CCAPP Seminars
manos

Superluminous Supernovae from Pair Instability and from SN ejecta - Circumstellar Matter Interaction: Insights from Light Curve Fits and Simulations

1/15/13
Manos Chatzopoulos
(U. of Texas, Austin)

Superluminous Supernovae (SLSNe) appear to come in two main spectroscopic flavors: hydrogen-rich (such as SLSN 2006gy, SLSN 2006tf, SLSN 2008am) and hydrogen-poor (such as SLSN 2007bi, SLSN 2008es, SLSN 2010kd). SLSNe are thought to be the result of either violent, massive SN ejecta - circumstellar interaction or massive stars that encounter electron-positron pair instability in their oxygen cores (Pair Instability Supernova; PISNe). In the present work, we use the observed LCs of 9 SLSNe and other objects in which CSM interaction might be relevant and fit a series of SN LC models for different power input mechanisms (radioactive decays of Ni-56 and Co-56, magnetar spin-down, CSM interaction) using a new x2 - minimization code. The analysis of the fitting results and the implied model parameters suggest that CSM interaction is the most likely mechanism for the majority of hydrogen-rich SLSNe. We suggest that hydrogen-poor CSM interaction can also be relevant in hydrogen deficient SLSNe, such as SLSN 2006oz and even SLSN 2007bi as an alternative to the PISN scenario. In addition, we present models of hydrogen-poor CSM shells ejected by Pulsational PISNe corresponding to rapidly rotating progenitors with smaller masses than in the non-rotating case.

SDSS

Galaxy evolution in groups and clusters in a hierarchical Universe

1/22/13
Andrew Wetzel
(Yale)

Satellite galaxies in groups and clusters play a critical role in the picture of galaxy evolution. As many as a third of all galaxies are satellites, and the quenching of star formation in satellites is the dominant process in building the red-sequence galaxy population at low mass. Furthermore, satellite quenching, and thus color transformation, governs the optical properties of galaxy clusters. I will present an observational and theoretical investigation into the evolution of star formation (and thus color) in satellite galaxies, using the Sloan Digital Sky Survey to examine satellites across a wide range of host halo masses, from massive clusters to the lowest mass dwarf galaxy groups in the local Universe. I will place these results in a fully cosmological context using a high-resolution simulation to track satellite orbits and infall times, showing that the star formation histories of satellites follow a delayed-then-rapid quenching (color transformation) scenario. I also will examine the curious evolution of satellites that orbit beyond the virial radius of their host halo.

elise jennings

Detecting modified gravity with improved models of redshift space distortions

1/29/13
Elise Jennings
Chicago/KICP

Forthcoming galaxy spectroscopic surveys will make high precision measurements of the clustering of galaxies on scales in excess of 100 Mpc/h. In particular, the distortion of clustering due to the peculiar motions of galaxies and the apparent scale of characteristic features in the galaxy distribution have been proposed as tests of the cosmic acceleration. To obtain meaningful and robust constraints on dark energy, we need to understand any systematics in these measurements. I will present the predictions for redshift space distortions from large volume and high resolution N-body simulations and discuss the accuracy of current models in recovering the growth rate. I will present predictions of the clustering of dark matter in redshift space in f(R) modified gravity and in quintessence dark energy cosmologies. Due to the size and resolution of these simulations, this is the first time that the nonlinear matter and velocity fields in this class of modified gravity models has been resolved to a high level of accuracy over a broad range of scales.

High precision cosmology with large-scale structure

2/6/13
Hee-Jong Seo
(BCCP, LBL/Berkeley)

Baryon acoustic oscillations (BAO) in large-scale structure provide an excellent standard ruler test to measure the cosmological distance scales (such as the angular diameter distance and the Hubble parameter), and therefore to probe dark energy properties. In this talk, I will discuss various aspects of BAO surveys, recent high-precision BOSS BAO measurements, and how reconstruction of BAO and other techiniques can be used to recapture cosmological information lost due to nonlinear evolution of structure.

The Interstellar Medium of Galaxies in the Epoch of Reionization

2/12/13
Joseph Munoz
(UCLA)

The ISM of z>~6 galaxies is a crucial element for understanding many important probes of cosmic reionization, such as recently discovered Lyman-break systems in the UDF, the evolution of Lyman-alpha emitters, Swift gamma ray bursts, and intensity mapping of galactic emission lines with ALMA, which can improve the reliability of 21cm tomography. I will present a new, fully-analytic framework for describing the ISM and molecular cloud properties of reionization epoch galaxies that includes physical processes from an enormous range of distance scales---from the tens of megaparsec regions over which cosmic variance operates to the tens of parsec-sized photo-dissociative regions inside molecular clouds---a span typically beyond the reach of numerical simulations. I will discuss the observational consequences of such a model, in particular, examining whether recent Chandra data can constrain the way gas is transported through the disk and making realistic predictions for detecting carbon emission lines with the JVLA and ALMA.

plot of research

Dark Matter Physics:
New Clues from Dwarf Galaxies?

2/19/13
Jesus Zavala Franco
(Waterloo)

The observed abundance and inner densities of dwarf galaxies have been enduring challenges for the otherwise-remarkably successful Cold Dark Matter (CDM) paradigm. They may put to the test two of the fundamental hypothesis underlying this paradigm: dark matter particles are collisionless and have low primordial thermal velocities. In this talk I will review the current status of these challenges and describe how Warm Dark Matter (WDM) and Self-Interacting Dark Matter (SIDM) models are viable alternatives to alleviate these problems, arguing that it is timely to study them as seriously as CDM in the context of galaxy formation.

Cosmic velocity flows in the Local Universe: methods, observations

2/26/13
Guilhem Lavaux
(Waterloo)

A valuable source of information on the distribution of dark matter and the growth of structures lies in the peculiar velocity field of the galaxies. After a short review on techniques available for their determination, I will present the results obtained on two recent techniques that I developed for estimating the large scale cosmic flows. These two techniques are based either on dynamical modeling of galaxy redshift catalog, or the detection of the kinetic Sunyaev-Zel'dovich signal in the Cosmic Microwave Background. I will show the results obtained when they are applied on the recent galaxy surveys and WMAP7 sky maps and some forecasts for PLANCK.

galaxy

A New Probe of Dark Matter in Spiral Galaxies

3/12/13
Sukanya Chakrabarti
(Rochester Institute of Technology)

The cold dark matter paradigm of structure formation is successful at recovering the basic skeletal structure of the universe -- the large-scale distribution of galaxies. However, agreement between theory and observation is less secure when this model is applied to galactic (and sub-galactic) scales. The "missing satellites problem" and discrepancies between the observed structure of dwarf galaxies and simulations have prompted us to develop an inverse method of characterizing galactic satellites. The extended atomic hydrogen disks of galaxies are ideal tracers of tidal interactions with satellites and the galactic gravitational potential well. Our "Tidal Analysis" method allows us to infer the mass, and relative position (in radius and azimuth) of satellites from analysis of observed disturbances in outer gas disks, without requiring knowledge of their optical light. I will present the proof of principle of this method by applying it to galaxies with known optical companions. I will also present our earlier prediction for a dim and yet undiscovered companion of the Milky Way. I will end by presenting preliminary work on the application of this method to characterize the density profile of the dark matter halo in spiral galaxies.

darkmatter

Simulations of Lyman-Alpha Forest with Nyx

3/26/13
Zarija Lukic
(LBL)

Measurements of the Lyman-alpha (Ly-a) forest in spectra of distant quasars open an additional avenue for probing cosmological parameters and the nature of cosmic expansion. The forest is particularly appealing as it probes higher redshifts than most other methods, z~2-4, but also because the signal comes from sampling lower densities of the cosmic web, with different systematic errors from probes tracing galaxies or galaxy clusters. On large-scales, the Ly-a power-spectrum is used as a standard ruler, measuring the BAO scale at high redshifts. On small-scales (the high-end of the power spectrum), the Ly-a forest allows one to constrain neutrino masses, and offers the promise of distinguishing between modified gravity and dynamical dark energy models. As a part of DOE's SciDAC-3 program, we have developed a new AMR hydro + N-body code called Nyx, with the primary goal of producing accurate predictions for the Ly-a forest under different cosmological models and UV background histories. In this talk I will present details of the code, show results from our first Ly-a simulations, and outline our future simulation campaign.

water purification system

The Earth's composition study using neutrino oscillation

3/28/13
Akimichi Taketa
(Earthquake Research Inst, U of Tokyo)

The neutrino oscillation is sensitive to the electron density. On the other hand, the neutrino absorption is sensitive to the nucleus density, i.e., mass density. If we know precise mass density from neutrino absorption or some Earth models, we will be able to measure the A/Z ratio deep inside the Earth and to study about the Earth's core/mantle composition using neutrino oscillation. In this talk, I will discuss about this geophysical potential of new generation neutrino detectors, PINGU and Hyper-Kamiokande.

charting

Few-body physics in the first few minutes:
Physics of light nuclei in the big bang

3/29/13
Kenneth Nollett
(Ohio University)

The earliest time in the history of the universe that is clearly probed by observations is the period from about one second to about fifteen minutes after the big bang, when the initial chemical composition of the universe was determined in big-bang nucleosynthesis (BBN). This was a much simpler time than today, so the physical processes that produced measureable amounts of only hydrogen, deuterium, helium, and lithium can be easily modeled. By comparing the isotopic compositions of these elements againts the model, we learn about the structure and contents of the universe. The light nuclei involved in BBN are interesting in their own right; theorists have only recently produced predictive models of how properties of light nuclei arise from those of neutrons and protons. I will discuss the use of BBN as a cosmological probe, emphasizing the connections between recent applications of the model and recent developments in the physics of light nuclei.

Bayesian Large scale structure

Large Scale Bayesian Inference in Cosmology

4/2/13
Jens Jasche
(IAP)

Already the last decade has witnessed unprecedented progress in the collection of cosmological data. Presently proposed and designed future cosmological probes and surveys permit us to anticipate the upcoming avalanche of cosmological information during the next decades. The increase of valuable observations needs to be accompanied with the development of efficient and accurate information processing technology in order to analyse and interpret this data. In particular, cosmography projects, aiming at studying the origin and inhomogeneous evolution of the Universe, involve high dimensional inference methods. For example, 3d cosmological density and velocity field inference requires to explore on the order of 107 or more parameters. Consequently, such projects critically rely on state-of-the-art information processing techniques and, nevertheless, are often on the verge of numerical feasibility with present day computational resources. For this reason, in this talk I will address the problem of high dimensional Bayesian inference from cosmological data sets, subject to a variety of statistical and systematic uncertainties. In particular, I will focus on the discussion of selected Markov Chain Monte Carlo techniques, permitting to efficiently solve inference problems with on the order of 107 parameters. Furthermore, these methods will be exemplified in various cosmological applications, raging from 3d non-linear density and photometric redshift inference to 4d physical state inference. These techniques permit us to exploit cosmologically relevant information from observations to unprecedented detail and hence will significantly contribute to the era of precision cosmology.

Three-Dimensional Simulations of Core-Collapse Supernovae

4/16/13
Sean Couch
(Chicago)

Core-collapse supernovae (CCSNe) are the luminous explosions that herald the death of massive stars. Neutron stars, pulsars, magnetars, and stellar-mass black holes are all born out of these explosions. Some Gamma-Ray Bursts (GRBs) have been associated with CCSNe, raising the possibility of a common progenitor for both. CCSNe are chiefly responsible for the production of elements heavier than iron throughout the universe; their importance in galactic chemical evolution cannot be underestimated. The first stars, expected to be relatively massive, likely ended as CCSNe as well. These bright events, occurring just a couple million years after the Big Bang, may be some of the most distant, observable objects in the universe with the upcoming James Webb Space Telescope. Despite the importance of CCSNe to our understanding of many aspects of the universe the mechanism that reverses stellar core collapse and drives supernova explosions is not fully understood. The CCSN mechanism is one of the most important challenges for modern computational astrophysics. I will discuss the current state-of-the-art of CCSN theory and simulation, with an emphasis on my recent work on three-dimensional CCSN simulations. I will highlight some of the most interesting and important questions supernova theorists are currently wrestling with, in particular the importance of fully three-dimensional simulations.

NASA NuSTAR images

Focusing Hard X-rays with NuSTAR: First Results from Multi-epoch Observations of the Bullet Cluster and NGC 253

4/22/13
Daniel Wik
(NASA Goddard)

NuSTAR is the first satellite capable of focusing hard (>10 keV) X-rays, increasing our sensitivity to point sources 100-fold and spatially resolving arcminute-scale objects for the first time. In this talk, I will briefly introduce the mission, its primary science goals, and a few early results from the various science working groups. I will then focus in depth on our observations of the massive, merging "Bullet" galaxy cluster and the nearby starburst galaxy NGC 253. In particular, the temperature structure of the Bullet cluster and early Chandra/NuSTAR joint spectroscopy of bright X-ray binary sources in NGC 253, along with prospects for interesting limits on diffuse inverse Compton emission from both, will be presented.

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Searches for Low-mass WIMPs with CDMS II and SuperCDMS

4/23/13
Richard Schnee
(Syracuse)

The Cryogenic Dark Matter Search experiment (CDMS II) was designed to directly detect WIMP dark matter by simultaneously measuring phonon and ionization signals caused by particle interactions in semiconductor targets, allowing event-by-event discrimination of signal from background via the relative sizes of the two signals. Data from the CoGeNT, CRESST II, and DAMA/LIBRA experiments have hinted at a low-mass WIMP signal. I will review these results and the (similarly sensitive) analyses performed by the CDMS II collaboration. Most recently, three WIMP candidate events were observed in a blind analysis of data from eight CDMS II Si detectors with an expected background <1 event. I will also describe the prospects for future searches at low mass with the SuperCDMS dark-matter program, including searches with the new interleaved detectors currently taking WIMP-search data in the Soudan Mine (with energy thresholds ~5x lower than previous detectors), as well as the long-term expected sensitivity of the SuperCDMS technology.

Lindley Winslow with quantum dots.

Next Generation Scintillation Detectors: Neutrinos and Nanotechnology

05/14/13
Lindley Winslow
(UCLA)

The last decade has seen a revolution in our understanding of the most mysterious of the Standard Model particles, the neutrino, and this last year has been no exception. In the last year, we have seen exciting results from both double beta decay experiments and experiments measuring the last mixing angle θ13. For the most part, the detectors responsible for these measurements use Cerenkov and scintillation light to detect neutrino interactions. The wavelength of this light is matched to the peak efficiency of photo-multiplier tubes. This technique has been finely tuned over the last decades, but no great leaps forward in efficiency have been achieved. Nanotechnology may hold the key to improving both scintillators and photo-detectors. In this talk, I will focus on one particular technology, semiconducting nanocrystals known as quantum dots, and their unique optical properties. I will discuss how their use could enhance the capabilities of new photo-detection technology, and address the needs of the next-generation neutrino experiments.

Lindley Winslow with quantum dots.

Precision physics with PINGU at the South Pole

05/21/13
Carsten Rott
(OSU)

The Precision IceCube Next Generation Upgrade (PINGU) is proposed as a new in-fill array for IceCube at the South Pole, Antarctica. The primary physics goal for PINGU is a determination of whether the neutrino mass hierarchy is normal or inverted using atmospheric neutrinos as the neutrino source. The determination of the mass hierarchy is one of the last unmeasured fundamental parameters in the neutrino sector. PINGU will also have an essential role in the search for low-mass dark matter and might enable us to probe the Earth interior by exploiting matter effects in neutrino oscillations. I will summarize the status of PINGU and present high-lights of on-going sensitivity studies.

Lindley Winslow with quantum dots.

Search for Spectral Lines with the Fermi Large Area Telescope

05/21/13
Andrea Albert
(OSU)

Recently a narrow spectral feature has been reported at 130 GeV localized in the Galactic Center. A gamma-ray spectral line is often considered a "smoking gun" for WIMP annihilations, so this would be a remarkable discovery if confirmed. However, the Fermi LAT Collaboration has searched for spectral lines from 5 to 300 GeV in 5 regions of interest and found no statistically significant (>3 sigma global significance) spectral lines. I will discuss what our search finds near 130 GeV and some of the systematic uncertainties we investigated that may induce false line-like features in our measured energy spectrum.

How Galaxy Physics Can Help Us Understand Weak Lensing

5/28/13
Eric Huff

While weak lensing measurements can provide a useful probe of galaxy-scale physics, it is not commonly appreciated that an understanding of galaxy-scale physics can in turn be used to dramatically improve weak lensing measurements. I will explain how galaxy scaling relations can enhance the weak lensing signal, and show recent results from a lensing magnification measurement using data from the Sloan Digital Sky Survey. The combination of magnification and shear measurements enabled by these techniques will permit significantly better weak lensing constraints on the distribution of mass on galaxy scales, in time for the newest generation of large, high-precision imaging surveys such as the Dark Energy Survey.

High Energy Neutrinos in IceCube

5/28/13
Ranjan Laha

Neutrino astronomy has long promised to reveal the astrophysical sites of particle acceleration and the nature of cosmic rays. With the completion of IceCube, this promise has turned into a reality. In this talk, I will first talk about the neutrino detection techniques in IceCube. I will then concentrate on the recently detected PeV events in IceCube. I will discuss the possible source spectrum and will then show how to robustly distinguish between the source spectrum in future.

Radio Detection of Ultrahigh Energy Neutrinos with ARA

6/4/13
Carl Pfendner

The Askaryan Radio Array (ARA) is an ultra-high energy (UHE) cosmic neutrino detector located at the South Pole. The cosmic ray flux cut off above primary energies of 10^19.5 eV leads us to expect a UHE neutrino flux due to the Greisen-Zatsepin-Kuzmin (GZK) effect. The detection of these UHE cosmic neutrinos will add to the understanding of the sources and physics of UHE cosmic rays. The radio Cherenkov technique is the most promising technique for a long term program to investigate the UHE cosmic neutrino flux. ARA uses this radio Cherenkov technique with radio frequency antennas deployed at a depth of 200m in the Antarctic ice. A prototype ARA TestBed station was deployed in the 2010-2011 season and the first three ARA stations were deployed in the 2011-2012 and 2012-2013 seasons. I will present preliminary results of the first neutrino search with ARA, using data taken from 2011-2012 with the ARA TestBed and describe the techniques that will be applied to data from the subsequently installed stations.

Probing the Anisotropy of the Milky Way Warm-Hot Gaseous Halo

6/4/13
Anjali Gupta

We have known for a while that our Milky Way, like other nearby galaxies, is missing most of its baryons and models of galaxy formation predict that they should reside in the circumgalactic medium (CGM), at warm-hot temperatures. This warm-hot gas in the CGM of the Milky Way is best characterized with absorption and emission studies at soft X-ray energies. Recently, we found that there is a huge reservoir of ionized gas around the Milky Way, with a mass of over 2 billion solar masses and a radius of over 100 kpc. This is an exciting new discovery, but it has its own caveats. We had assumed an average, but constant value of the emission measure for all the sight-lines. By comparing absorption and emission measurements from adjacent fields I will show that the warm-hot gas in the CGM of the Milky Way is not distributed uniformly. I will discuss the anisotropy of the Milky Way warm-hot halo and its effect on the contribution to the missing baryon problem.

Probing the Warm-Hot Intergalactic Medium using Weak, Distributed Metal Absorption -- Early Stages of the project

6/11/13
Stephan Frank

The incomplete census of baryons in the low-redshift Universe is one of the outstanding problems of modern cosmology. Up to 50% of baryons are as yet unaccounted for. It is thought that the primary reservoir of missing baryons is the warm-hot intergalactic medium (or WHIM). This gas is thought to be at temperatures 5 < log T(K) < 7 mainly due to shock-heating during gravitational collapse. Metal ionization species are an ideal probe of these physical conditions. They may be seen via absorption in UV spectra of quasars.

Surveys are underway to search for these metals by identifying individual absorption lines in COS spectra. We propose to measure the signal of weak, distributed absorption between these lines. In doing so, we expect to probe an equally large portion of the baryon budget as found by these surveys. We intend to achieve this by use of searches for correlated absorption that we have refined ourselves.

Probabilistic Image Reconstruction with Radio Interferometers

6/11/13
Paul Sutter

The next generation of radio interferometers will image a wide variety of astrophysical and cosmological sources, delivering an incredible amount of raw data in the process. To enable effective science, we must deconvolve the noisy, incomplete data in a robust, data-driven, and efficient way. In addition, to perform quantitative analysis, we must have methods which deliver uncertainty information about the final processed images. Gibbs sampling, a technique widely used in CMB analysis, can potentially meet all these needs. This Bayesian method is scalable and flexible, requires minimal priors, and provides complete posterior information. We show several examples of using Gibbs sampling to reconstruct simulated images in realistic scenarios and compare Gibbs sampling to traditional deconvolution approaches.

Recent Results from IceCube

6/12/13
Albrecht Karle
(University of Wisconsin)

The IceCube neutrino detector, with 1 Gton of instrumented volume the largest neutrino detector ever built, was completed in December 2010. Today, 3 years of data have been recorded with the almost final and final configurations of IceCube. The very intriguing observation of two events at ~1 PeV energy reported in 2012 was followed up with a targeted search at lower energies. The collaboration recently reported new results with an additional 26 events in the energy range from around 50 TeV to PeV from data taken in the same period. The results form evidence for the presence of astrophysical neutrinos events in the sample. I will discuss the recent results of IceCube and will put these findings and in perspective to various searches for high energy neutrinos with IceCube.

The All Sky Automated Survey for Supernovae

6/18/13
Ben Shappee
(OSU)

The All Sky Automated Survey for Supernovae (ASAS-SN or "Assassin") is a long-term project to monitor the whole sky to find nearby supernovae (SNe) with a global network of fully-robotic telescopes. Many distant SNe observed by volume-limited surveys, including some of the most interesting events, are seen to occur in the outskirts of galaxies or in dwarf galaxies. Locally, most of these SNe are currently being missed by amateurs and galaxy-targeted SN surveys, but could be detected by an all-sky survey. The north ASAS-SN unit, Brutus, recently finished commissioning and is located on Mount Haleakala on Maui, Hawaii. Brutus is equipped with two telescopes on a common mount. Each telescope has a 14cm lens, a large 4.474.47 square-degree field-of-view, and a limiting V-band magnitude of 17.5 allowing us to survey the sky every 3-5 days. Since April of this year Brutus has lead to 8 ATELs, 16 bright CV discoveries, 1 "changing look" AGN, and the discovery of a Type Ia Supernova near maximum-light.

Hot Chromospheres on Ultracool Dwarfs

6/18/13
Sarah Schmidt
(OSU)

Despite having very cool atmospheres, Ultracool Dwarfs show evidence of chromospheric emission, generated by the interaction of magnetic fields with ionized material in their atmospheres. I investigate chromosphres on Ultracool Dwarfs using the presence and strength of the H-alpha emission line from SDSS spectra. Using one-dimensional atmosphere models, I place constraints on the chromospheric temperature structures and filling factors needed to produce the observed H-alpha emission strength. While chromosphreic activity is more common on early-L dwarfs than late-M dwarfs, the chromospheres of early-L dwarfs are much cooler and less extended than those of late-M dwarfs.

Microlensing Planet Discovered Using Data From One Telescope

6/25/13
Radek Poleski
(OSU)

Almost all the microlensing planets discovered so far relied on data collected by different groups and analyzed jointly. The growing capabilities of survey groups, which discover microlensing events, allows finding the planets using survey-only data. I present the analysis of one such case. Data from the OGLE telescope allowed not only detecting the planet but also measuring the second order effects. The measured microlensing parallax places the stellar mass at M/K dwarf boundary. The planet turns out to be a super-Jupiter orbiting the star beyond a snow line, i.e. the third such planet around low-mass star.

Exploring exoplanetary systems beyond 1AU with WFIRST

7/2/13
Matthew Penny
(OSU)

WFIRST (the Wide Field InfraRed Survey Telescope) will be NASA's next flagship astrophysics mission after JWST. Its primary instrument will be a large-format high-resolution near-infrared imager and slitless spectrometer. A primary goal of WFIRST will be to perform a high-cadence microlensing survey of the Galactic bulge to search for low-mass exoplanets beyond the ice line. This poster highlights some of the expected results of the WFIRST exoplanet survey. For example, at Earth-mass, the survey will probe the abundance of planets from less than 1 AU outwards, including free-floating planets. In its peak sensitivity range of ~2-5 AU, WFIRST will be sensitive to planets with masses lower than Mercury. Overall, WFIRST is expected to detect several thousand bound planets, as well as several thousand free-floating planets.

Resolving small scale Dark Matter structures using Indirect Dark Matter Detection

7/2/13
Kenny Ng
(OSU)

Dark matter annihilations from cosmological dark matter halos contribute to the Isotropic Gamma-Ray Background (IGRB) measured by the Fermi Gamma-ray Telescope. The expected gamma-ray intensity depends on both particle physics and astrophysics. Particle physics determines the annihilation rate given the density environment of dark matter, while the astrophysics determines the density distribution of dark matter in the universe. Comparing the IGRB to the gamma-ray observations from the Galactic Center may help to disentangle the particle physics and the astrophysics, as well as shedding light on some tantalizing dark matter annihilation signals.

2012 Reverberation Mapping Campaign

7/9/13
Gisella DeRosa

I will present results from our latest reverberation mapping program, carried out over January-April 2012. During the 120 days of the campaign, we collected both spectroscopic and photometric data for nine Seyfert 1 galaxies from various observatories. We have obtained high sampling-rate light curves of the Hbeta emission line and of the AGN continuum at 5100 Ang for seven AGNs: NGC 3227, NGC 3516, NGC 4151, NGC 5548, Mrk 374, Mrk 478, Mrk 704. I will discuss the analysis of the light curves and the derived time lags between continuum and line emission variation as well as the estimated black hole masses.

Counting Hydrogen and Oxygen Atoms for Metallicities

7/9/13
Kevin Croxall

The metal content of nearby galaxies can be determined in in multiple ways. However these methods require different assumptions, which may or may not be valid, and measurements, not all of which are easily obtained. Consequently, the calibration of abundances in nearby galaxies remains uncertain. I will review current methods of determine the metallicity of HII regions and discuss efforts to significantly constrain the calibration of these scales.

The First Moments of Stellar Death

7/10/13
Tony Piro
(Caltech)

Wide-field, high cadence surveys are allowing us to catch supernovae earlier than ever, often days if not hours after the they first begin. Theoretical work focusing on this early phase of stellar explosions is critical for (1) deriving constraints from observations, (2) predicting and interpreting new discoveries, and (3) helping guide the strategies of future observational efforts. I will discuss theoretical research in each of these areas, including showing how we are beginning to directly measure the properties of stars before they die and investigating how we may potentially observe the elusive events that mark black hole formation.

Dark Matter Searches with the Gamma-ray Anisotropy

7/16/13
Sheldon Campbell

Astrophysical gamma-ray experiments are characterizing the gamma-ray sky. Wide-angle experiments like the Fermi-LAT are especially suited for measuring the angular power spectrum. Since the dark matter distribution is predicted to have a different angular distribution in the sky than other astrophysical gamma-ray sources, the angular signature is sensitive to photon production from dark matter annihilation. In this talk, I will discuss the sensitivity of the gamma-ray angular power spectrum to dark matter annihilations, present some dark matter constraints based on the published experimental measurements, and compare these constraints to the more traditional dark matter searches.

Near-Infrared DIBs in the SDSS-III APOGEE Survey

7/16/13
Gail Zasowski

APOGEE is an ongoing, near-IR, high resolution spectroscopic survey of 100,000 giant stars in the Milky Way's bulge, disk, and halo, which probes both low- and high-reddening environments and is providing us with a unique, homogeneous view of the Milky Way. This dataset is also well-suited to a search for interstellar absorption lines. Recently, Geballe et al. (2011, Nature) reported the first detection of diffuse interstellar bands (DIBs) at wavelengths longer than 1.5 microns along a few lines of sight. Our analysis of the APOGEE spectra has resulted in the detection of such near-IR DIBs along several thousand sight-lines, thus increasing the number of detections in this regime by more than two orders of magnitude. After describing our detection method, I will present correlations between these DIBs and other ISM tracers in both abundance and kinematics, which give us new insights into the environment and properties of these absorption features.

Evidence for High-Energy Astrophysical Neutrinos at IceCube

7/19/13
Dr. Nathan Whitehorn
(University of Wisconsin, Madison)

The origin of high-energy cosmic rays is one of the most persistent mysteries in physics. Neutrinos, as neutral tracers of hadronic acceleration, may offer a new and unique window into this problem and others in high-energy astrophysics. I will discuss recent results from the antarctic IceCube neutrino observatory, the first operating gigaton-scale neutrino detector, showing first evidence for a population of extremely high energy neutrinos (100+ TeV) that cannot easily be explained by processes occurring in cosmic ray showers in the Earth's atmosphere and may be the first evidence for a population of high-energy neutrinos of extraterrestrial origin.

charting

Can we do lensing with DECam?

7/23/13
Peter Melchior

DECam, the newly build camera of The Dark Energy Survey, has seen first light in September 2012 and has, since then, gone through an intense phase of Science Verification, which provides us with crucial information to understand and improve the telescope performance for the survey start in late summer 2013. During this phase, we observed five galaxy cluster fields to study the photometry and lensing performance of the new instrument, seeking to utilize its remarkable Field-of-View of more than 3 square degrees to probe massive clusters and their environment. I will present the first weak lensing results of the DES, and discuss several - partially unsolved - issues that hamper the analysis.

Ultra-High Energy Cosmic Rays: Nuclear Mass Composition and Atmospheric Interactions

7/30/13
James Stapleton

The charge and atomic number of Ultra-High Energy Cosmic Ray (UHECR) nuclei (E>10^18 eV) cannot be directly measured. Astrophysical constraints reduce the set of possibilities to stable atomic nuclei (with 1<=A<=56), but limitations in our understanding of atmospheric cascades confound most attempts to clearly identify UHECR nuclear masses. Determination of these masses would yield important information about their sources (which are still not understood) and their interactions with the extragalactic background light and cosmic microwave background during their transit through extragalactic space. I will present an attempt to further constrain UHECR composition using Xmax (the cascade's penetration depth into the atmosphere) using data from the Pierre Auger Observatory. We construct a linear transformation which computes mass distribution moments from Xmax distribution moments. While this utilizes atmospheric cascade simulations, we show how to reduce the impact of uncertainties in these simulations. This is done by relating the Xmax distribution's skewness to statistical fluctuations in early cascade interactions.

J-PAS: The Javalambre-Physics of the Accelerated Universe Astrophysical Survey

8/6/13
Txitxo Benitez
(Instituto de Astrofisica de Andalucia)

The Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5m telescope, using a set of 54 narrow band and 5 broad band filters over a 1.2Gpix, 4.7deg2 camera. Starting in 2015, J-PAS will image 8500deg2 of Northern Sky and obtain 0.003(1 + z) precision photometric redshifts for 9 x 107 galaxies, about 50 times more than the largest current spectroscopic survey, sampling an effective volume of ? 14 Gpc3. In addition J-PAS will also carry out a SNIe survey, a cosmic shear survey (thanks to the superb seeing at Javalambre) and a cluster survey, exploring the four main Dark Energy probes. In fact, and thanks to its innovative design, J-PAS will be the first experiment capable of reaching Stage IV according to the Dark Energy Task Force classification, several years before other projects like Euclid or LSST start their operations. The instrumental development of this project involves a small fraction of the cost and complexity of a high multiplexing spectrograph, yet it will produce data which enable a much wider range of Astrophysical applications: J-PAS effectively uses a 4.7deg2 "IFU" which will produce a low resolution 3D image of the Extragalactic Northern sky. Our survey will have a lasting legacy value, serving as a fundamental dataset for future cosmological projects.

A Multi-wavelength Approach to AGN Selection using UV to Mid-infrared SEDs

8/13/13
Sun Mi Chung

Extragalactic surveys have traditionally been either wide and shallow, or narrow and deep. Wide/shallow surveys such as the SDSS and the 2DF Galaxy Redshift Survey allow us to study large populations of both galaxies and luminous AGN, while narrow/deep surveys such as COSMOS and DEEP2 can probe fainter populations. However, the relative rarity of AGN makes it difficult to fully characterize AGN in deep fields or to account for faint AGN in shallow fields. The NOAO Deep Wide-Field Survey (NDWFS) in the 9 square degree Bootes field allows us to explore a cosmologically significant volume with data that is both deep and extensive in wavelength coverage. Utilizing 17 bands of data from the ultraviolet to the mid-infrared, we fit galaxy, AGN, stellar, and brown dwarf templates to the spectral energy distributions of ~800000 sources. By fitting these templates to the data we are able to cleanly separate galactic from extragalactic sources for most of the sample. We also compare the SED fits for a galaxy-only model and a galaxy+AGN model and confirm that SED fitting can be successfully used as a method for identifying large populations of AGN, including extended AGN with significant contributions from the underlying host galaxies.

Applications of Lensed Quasars' Variability

8/13/13
Ana Mosquera
(OSU)

Flux variability of lensed quasars can be used as a fun and fancy way to study the structure of galaxies and quasar accretion disks. These fluctuations are a combination of the intrinsic variability of the quasar, from which it is possible to measure time delays and determine the dark matter halo structure of the lens galaxy, and microlensing variability induced by the stars and compact objects in the lensing galaxy, from which we can measure accretion disk sizes, the mean mass of the stars in the lens galaxy, and the dark matter mass fraction near the lensed images. In my talk I will discuss where these cool measurements are leading us, and the current status of our target selection and follow up.

Cosmological imprints in the intrinsic alignments of Luminous Red Galaxies

8/20/13
Elisa Chisari
(Princeton)

The tidal alignment model has been shown to reproduce the intrinsic alignments of Luminous Red Galaxies on large scales. While intrinsic alignments are usually thought of as a contaminant of cosmic shear measurements, they encode cosmological information and information about the formation history of galaxies. In this talk, I will discuss prospects of using the intrinsic alignments of Luminous Red Galaxies as a probe of baryon acoustic oscillations and primordial non-gaussianity with ongoing and upcoming surveys.

The large-scale structure of the Universe as seen by Planck.

8/27/13
Aurelien Benoit-Levy
(University College London)

One of main results of the 2013 data release of the Planck Collaboration is the first full-sky reconstruction of the lensing potential. The lensing potential is the projection on the sky of all the matter density fluctuations from today up to the last scattering surface and therefore constitutes the most complete information on the matter distribution at high redshift. In this talk, I will explain how the lensing potential, a quantity related to the large-scale structure of the Universe, can be reconstructed from observations of the anisotropies of temperature of the Cosmic Microwave Background (CMB) using the Planck data. I will then present in details the Planck lensing map and describe its use for cosmological studies, from improved constraints on cosmological parameters to joint analysis with current and future large-scale structure surveys.

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Probing Dark Matter on Small Scales with Weak Lensing

9/3/13
Matthew George
(UC Berkeley)

The mass profile of galaxies and clusters on small scales is important to a wide variety of problems in astrophysics and cosmology. Gas cooling and stellar feedback directly impact the dark matter distribution, and uncertainty in the stellar initial mass function makes it difficult to separate baryonic and dark components. The abundance of substructure and the inner halo slope are also sensitive to dark matter self-interactions. Uncertainties in these effects will hinder gravitational lensing experiments aiming to constrain dark energy with cluster masses and cosmic shear. I will discuss challenges and opportunities for addressing these issues with weak lensing on small scales. In particular, I will discuss results from a study of halo miscentering with a galaxy group catalog, and forecasts for combining shear and magnification with dynamical masses from current and future surveys. I will also present a novel technique that uses kinematic information from background sources to infer their intrinsic shapes, greatly improving the lensing signal-to-noise per galaxy and enabling weak lensing measurements from individual galaxies.

Possible Signatures of Exotic Dark Matter in Stars

9/10/13
Andrew Zentner
(PITT PACC)

There has been a long-standing quest to identify the dark matter. Numerous recent developments, including recent recent results from dark matter direct detection experiments and indirect searches for dark matter by the Fermi Gamma-ray Space Telescope (FGST), have spurred interest in exotic models of dark matter. First, I will discuss Asymmetric Dark Matter. A possible candidate for the low-mass (< 20 GeV) dark matter that would be consistent with both the events observed in the CoGeNT & CDMS direct detection experiments while evading constraints on annihilation rates from non-detection of gamma-rays by FGST is Asymmetric Dark Matter (ADM). In ADM, the contemporary dark matter consists of a particle, but not its anti-partner so it does not annihilate (the symmetric portion of the population annihilated in the early universe). Nevertheless, I will discuss how Asymmetric Dark Matter may leave its signature on stellar evolution giving a potential astrophysical signature of such a dark matter candidate. Time-permitting, I will also discuss self-interacting dark matter (SIDM), which is a dark matter particle with a large cross section (~1 barn) for scattering with itself. SIDM has been invoked as a possible means to alleviate some of the small-scale "challenges" to standard Cold Dark Matter (CDM) cosmology. I will discuss how SIDM is captured within the Sun and how neutrino telescopes can provide complementary constraints on some SIDM candidate models.

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The Unbearable Lightness of Being: Direct detection of light dark matter

9/16/13
Felix Kahlhoefer
(U of Oxford, UK)

Motivated by the recent observation of a signal in the Si detectors of the CDMS-II experiment, I will review the difficulties of direct detection for light dark matter. While the observed events are consistent with being nuclear recoils due to scattering of Galactic dark matter particles, there is significant tension with the upper bounds from the XENON10 and XENON100 experiments. I will discuss the underlying assumptions for these results and point out under what conditions the tension between these experiments can be ameliorated or resolved. A particular focus will be on experimental uncertainties (for example concerning the ionisation yield Q_y) and uncertainties related to the dark matter velocity distribution. Finally, I will discuss various particle physics modifications of the interactions between DM and SM quarks which can bring XENON10/100 and CDMS-II into better agreement.

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Radio frequency interferometry for measuring Antarctic albedo and detecting cosmic ray events

9/18/13
Jessica Stockham
(U of Kansas)

The ANtarctic Impulsive Transient Antenna (ANITA) experiment, a balloon-borne suite of horn antennas, is designed to detect radio frequency (RF) signals from the interaction of neutrinos with nucleons in the Antarctic ice sheet. Subsequent to the the ANITA II 2008-2009 flight, no neutrino events were discovered, but analysis did show the detection of cosmic ray air shower events. The majority of these events were detected as reflections from the ice surface. Reconstructing these reflected events requires analysis and modeling of the reflection properties of the air-ice interface. Using data obtained during the ANITA II 2008-2009 flight, the direct and reflected solar signals are employed to estimate the the power reflection coefficients as a function of incident elevation angle. The initial results of this analysis are discussed along with issues arising from the interferometric techniques. Current progress toward implementing a different interferometric technique, triple correlation, is presented as a method to potentially improve the analysis.

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Revised predictions of ultra-high-energy neutrinos from gamma-ray bursts and the cosmic ray-neutrino connection

9/23/13
Mauricio Bustamante

The recent detection of ultra-high-energy (UHE) neutrinos by IceCube has marked the start of a new era: it is possible that the long-sought UHE neutrinos from cosmic accelerators are now starting to be seen. Among the accelerator candidates, gamma-ray bursts (GRBs) stand out as some of the most attractive: from their observed high luminosities (~10^52 erg/s) and inferred large magnetic fields (~10^5 G), they are likely sites where highly-accelerated protons (~10^21 GeV) could create neutrinos of similar energy through proton-photon interactions. The non-observation of neutrinos associated with GRBs has recently ruled out the simplest models of UHE neutrino emission from these sources. However, by taking greater care of the particle physics involved, the expected flux from a more sophisticated emission model lies still comfortably one order of magnitude below the current upper bounds, as shown by the recent ANTARES results. In this talk, I will briefly introduce NeuCosmA, our revised model of neutrino emission. Also, I will succinctly introduce a generalised model of cosmic ray (CR) emission from GRBs which allows for protons to "leak out" of the source, in spite of the magnetic confinement. Finally, I will touch upon the cosmic ray-neutrino connection, assuming a common origin for them in GRBs, and argue that the current UHECR observations and the bounds on the UHE neutrino flux might already be enough to put tension on several possibilities of CR and neutrino emission and propagation.

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SNO+ and the search for the Majorana neutrino

9/24/13
Logan Sibley
(U Alberta)

One of the leading unanswered questions in the field of neutrino physics is whether the neutrino is equivalent to its anti-particle, a so-called Majorana fermion. The most promising experimental method to determine the nature of the neutrino is to search for the process of neutrinoless double beta decay, where two neutrons in an isotope decay to two protons via neutrino exchange, emitting just two electrons and violating lepton number conservation in the process. The field is currently rife with experiments exploiting this idea. To date, however, there has been only a single claim of observation from a subgroup of the Heidelberg-Moscow experiment investigating 76Ge, reporting a half-life of 2.23x10^25 years and effective Majorana neutrino mass of 320 meV. Recent results from the GERDA experiment, using refurbished Ge crystals from Heidelberg-Moscow, strongly disfavour this claim, leading to a combined Ge experiment half-life limit at 90% confidence of 3.0x10^25 years. Current experiments investigating 136Xe also disfavour this claim of observation. Joining the current generation of experiments with the aim of pushing down the effective Majorana mass limit, SNO+ is a kilotonne-scale liquid scintillator neutrino detector housed 2 km underground in Vale Canada Ltd.'s Creighton Mine near Sudbury, Ontario, Canada. Through re-purposing existing hardware in place for the now decommissioned Sudbury Neutrino Observatory (SNO), and employing a rigourous materials purification and selection program, SNO+ will investigate neutrinoless double beta decay of 130Te. Owing to its size, SNO+ expects a sensitivity to the effective Majorana neutrino mass below 100 meV with a 0.3% loading of natural Te after several years of data collection. Designed as a general purpose detector, SNO+ also has a robust physics program that includes investigations of solar and supernova neutrinos, and reactor and geo anti-neutrinos. Construction of the detector is nearly complete, with the first water-fill commissioning phase set to begin at the end of this year with the neutrinoless double beta decay phase following in late 2014. This talk will present a short overview of neutrinoless double beta decay and outline the current status and physics goals of the SNO+ experiment.

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Revealing Core Collapse Supernova Progenitors Without Seeing Them

10/1/13
Iair Arcavi
(UC Santa Barbara)

Identifying the progenitors of the various types of core collapse supernovae (SNe) is an outstanding problem, hindering progress towards understanding the explosion mechanisms of these events. Direct progenitor detections are limited to few nearby cases, and this method has so far only robustly established the connection between red supergiants and Type IIP SNe. Statistical methods allow for some constraints to be put on progenitor scenarios of other SN types, with large samples illuminating certain aspects of the roles of binarity, mass and metallicity. In addition, new surveys such as iPTF are finding supernovae at very early times, a mere hours to days after the explosion. Observations on these timescales can probe the shock cooling emission, constraining the progenitor radius, the explosion physics and also Ni mixing. Together, these methods are teaching us about the progenitors of many SN types.

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New Relics from Inflation

10/2/13
Liang Dai
(Johns Hopkins)

Cosmological observations strongly support the theory that an inflationary phase in the early Universe seeded the density inhomogeneities of the present Universe. However, the underlying physics that drove inflation remains poorly understood. A variety of motivations lead us to consider the possibility that inflation may have involved more than just one fundamental field. If so, then it is important to understand the possible imprints of these inflation relics on cosmic structures, as these may, if observed, help reveal the fundamental mechanism of inflation. I will present two examples of such imprints from inflation. One is a three-point correlation between some 'fossil' field and the density perturbation. Such a correlation can give rise to modulations over the sky of power in the cosmic microwave background anisotropies. The other example involves a correlation between the inflationary gravitational-wave background and primordial density perturbations. I will explain how gravitational waves generated by inflation can result in a physically-measurable quadrupolar anisotropy in the galaxy power spectrum.

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Newborn Pulsars as sources of Ultrahigh Energy Cosmic Rays

10/4/13
Ke Fang
(Chicago)

The workings of the most energetic astrophysical accelerators in the Universe are encoded in the origin of ultrahigh energy cosmic rays (UHECRs). Current observations by the Auger Observatory, the largest UHECR observatory, show a spectrum that agrees with an extragalactic origin, as well as an interesting transition in chemical composition from light element to heavier element as energy increases. Candidate sources range from young neutron stars to gamma-ray bursts and events in active galaxies. In this talk, we will discuss newborn pulsars as the sources of ultrahigh energy cosmic rays. We will show that a newborn pulsar model naturally injects heavier elements and can fit the observed spectrum once propagation in the supernova remnant is taken into account. With the proper injection abundances, integrated cosmic rays from the extragalactic pulsar population can match observation in all aspects - energy spectrum, chemical composition, and anisotropy. We will also examine the fingerprints of their Galactic counterparts on cosmic ray spectrum . Lastly, we will discuss the multi-messenger smoking gun of this scenario - the detectability of high energy neutrinos from pulsars and magnetars.

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Bright and dark: Satellite galaxies as a test of galaxy formation and the nature of dark matter.

10/4/13
Anna Nierenberg
(UC Santa Barbara)

I present our recent measurements of the spatial distribution and the cumulative luminosity function of satellites up to a thousand times fainter than their hosts, as a function of host stellar mass and morphology between redshifts 0.1 and 0.8, using imaging from the COSMOS fields and a rigorous statistical analysis. I will demonstrate how these measurements provide powerful new constraints for abundance matching and cosmological simulations in the context of both warm and cold dark matter, and how future measurements of faint satellite colors using CANDELS, will provide important distinguishing power between warm and cold dark matter models. In addition, I will present results from a complementary gravitational lens modeling project in which we use spatially resolved spectra obtained with OSIRIS at Keck to place new constraints on the subhalo mass function.

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Distribution function approach to redshift-space distortions

10/15/13
Zvonimir Vlah
(ITP Zurich)

In galaxy clustering surveys redshift corresponds to the true distance according to the Hubble Law. In addition, peculiar velocities induced by the local gravitational potential are not associated with the Hubble flow and can cause distortions in redshift space. We study these distortions in phase space distribution function approach in order to model the power spectra of dark matter and halos. In this approach RSD of dark matter halos can be written as a sum over density weighted velocity moments correlators, with the lowest order being density, momentum density and stress energy density. Modelling of these contributing terms is done by combining perturbative methods and non-local biasing model to connect halos to the underlying dark matter distribution. In modelling the isotropic part of the RSD power spectrum we go beyond the Poissonian estimates of shot noise and allow for the scale dependence seen in the N-body simulation data. We present the results of RSD model for multipoles as well as dependence of the power spectrum on the amplitude and direction of the Fourier modes. Transforming these we also obtain the results in configuration space. In addition to the power spectra we also show the models for the velocity statistics in the resdhift space.

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Exploring the Extreme Universe with Fermi

10/15/13
Julie McEnery
(University of Maryland)

Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory, review the science highlights and discuss future opportunties with Fermi.

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Imprint of unstable dark matter on large-scale structure and implications for subhalo properties

10/22/13
Mei-Yu Wang
(Indiana, Pittsburgh)

Although cold dark matter is known to describe large-scale observations well, its agreement with data on galactic scales is less clear. A possible solution to the galactic scales issues relies on altering the nature of dark matter, such as making it warm or self-interacting. To constrain these different dark matter models, it is important to look for complementary astrophysical constraints. I discuss a class of unstable dark matter models in which a dark matter particle decays into a slightly less massive stable dark matter particle and a comparably light particle, with lifetime the order of the age of the Universe. I will show that by combining SDSS Lyman-alpha forest measurements with WMAP data, we can place interesting and competitive limits on decaying dark matter (DDM) models. Because of its late-decay nature, this class of DDM models can have significant impact on galactic substructure while agreeing with observations of the high-redshift intergalactic medium (IGM) distribution. I will discuss the predictions of DDM models on the galactic scales and compare them with those from other DM models. I will also discuss possible improvement in model constraints using late-time phenomena with forthcoming weak lensing data and also the newly-released BOSS Lyman-alpha forest measurement.

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Mapping the z~2 Cosmic Web with Lyman-alpha Forest Tomography

10/24/13
Khee-Gan Lee
(Max Planck Inst for Astronomy)

I will discuss the technique of Lyman-alpha forest tomography, in which the Lyman-alpha forest absorption from an extremely dense grid (>500 per sq deg) of background sources is used to make a full 3D 'tomographic' map of large-scale structure at z~2. Using empirical luminosity functions of QSOs and LBGs, I will show that at apparent depths of g~24, the background sources are separated by comoving transverse distances of ~3 h^-1 Mpc thus enabling mapping on that resolution. Using simulations, I will show that just S/N~4 per angstrom on g=24 background sources is sufficient to generate maps with ~3 h^-1 Mpc comoving. This requires just several hrs of integration on existing spectrographs on 8-10m telescopes, e.g. VLT-VIMOS and Keck-LRIS. I will introduce CLAPTRAP, a survey to map out 1 sq deg in the COSMOS field over a comoving volume of 10^6 h^-3 Mpc^3. The resulting maps can be used to study z~2 properties as a function of their large-scale environment, characterize the topology of large-scale structure, and find galaxy protoclusters.

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Probing the initial conditions of the Universe using large scale structure

10/29/13
Nishant Agarwal
(Carnegie Mellon)

Primordial non-Gaussianity induces a scale-dependent bias in large scale structure (LSS) data. Recent work has shown that the exact form of this scale-dependence also helps distinguish between scenarios where a single field or multiple fields contribute to the curvature fluctuations, and encodes information about the initial state of inflationary perturbations. I will discuss work in which we use photometric data of luminous red galaxies and quasars in the Sloan Digital Sky Survey Data Release Eight (SDSS DR8) to constrain primordial non-Gaussianity and the scale-dependence of the bias, and its implications for different models of inflation and single field inflation with generalized initial conditions. For reliable cosmological parameter estimation from LSS, it is extremely crucial to account for various sources of contamination in the data --- I will also discuss a method to characterize unknown systematics which may persist in the data after correcting for known sources of contamination.

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A Nearly Gaussian Hubble-patch in a non-Gaussian Universe

11/5/13
Marilena Loverde
(Chicago)

The statistics of density perturbations in our local patch of the universe may look radically different from those in the universe at large --- something called ``super cosmic variance." In particular, even a small level of non-Gaussianity can cause observations in our Hubble volume to be biased by mode coupling. The bias depends on the background value of the curvature potential -- something that is locally unobservable -- and can be large if the entire post inflationary patch is large compared with our Hubble volume. I present a few examples in which the statistics of density perturbations in our Hubble patch appear nearly Gaussian and consistent with observations, despite the fact that the statistics in the larger post-inflationary volume look very different. Finally, I'll show an explicit example, the curvaton scenario, where the mode-coupling bias can be understood simply.

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A multi-messenger quest for the sources of the highest energy cosmic rays

11/8/13
Foteini Oikonomou
(University College London)

The origin of ultra high energy cosmic rays (UHECRs) remains unknown despite decades of experimental and theoretical research; their discovery will bring to light the nature of the Universe's most violent accelerators. In this talk I will discuss the observable signatures of UHECRs that can be used to constrain the nature and distribution of their yet unknown sources, focusing on the constraints imposed by the arrival directions of the highest energy cosmic rays detected at the Pierre Auger observatory in Argentina. Constraints on the sources of UHECRs may also come from the secondary particles (gamma-rays and neutrinos) that UHECRs produce during their propagation. I will present the results of a search for the signatures of UHECR acceleration in the gamma-ray spectra of blazars and discuss the implications for the detectability of such signatures with current and upcoming gamma-ray instruments.

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Dissecting Galaxies With the Hubble Space Telescope

11/13/13
Julianne Dalcanton
(U of Washington)

7th Annual R. Jack and Forest Lynn Biard Cosmology and Astrophysics Lecture
Galaxies are complex systems of stars, gas, and dark matter. These three major components interact in many different ways, leading galaxies to have the structure and motions we see today. I will discuss the current paradigm for galaxy formation, and show how some of the most beautiful Hubble Space Telescope observations can be used to extract detailed histories of the nearest galaxies, providing some of the most rigorous constraints on the physics that controls galaxy formation.

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Gas Retention and Accumulation in Dwarf Galaxies: Implications for Star Formation

11/19/13
Jill Naiman
(UC Santa Cruz)

The effective supply and retention of gas in shallow gravitational potentials is a problem with implications in a diverse set of astrophysical systems. In particular, the magnitude of gas flows into mature dwarf galaxies can have large impacts on the star formation histories in these systems. In this talk, computational techniques will be used to show how such such weakly bound gravitational structures might be able to accumulate gas effectively. The implications for star formation in dwarf galaxies after their incorporation into a larger host halo will be presented.

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Cosmic Voids: Tracers of Large-Scale Structure

12/5/13
Nico Hamaus
(Paris Institute of Astrophysics)

Redshift surveys measure the location of millions of galaxies in the observable Universe, thereby constructing a three-dimensional map of its large-scale structure. This structure is characterized by dense clusters of galaxies, connected by filaments and sheets of lower number density. The remaining and dominant volume within this cosmic web is taken up by voids, vast regions of relatively empty space. While clusters, filaments and sheets have all entered different stages of non-linear evolution during cosmic history, voids represent structures that more closely related to the initial conditions of the Universe. I will discuss the prospects of considering cosmic voids as tracers of large-scale structure. While the clustering of voids alone yields a poor signal-to-noise ratio, when combined with the clustering statistics of galaxies, some interesting features emerge that may be useful for cosmological applications in the future. I will present some recent results obtained from numerical simulations and discuss their implications.

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Real-space density profile reconstruction of stacked voids

12/6/13
Alice Pisani
(Paris Institute of Astrophysics)

In this talk I will briefly introduce the use of cosmic voids to constrain cosmology. I will then present a non-parametric, model-independent method to reconstruct the spherical density profiles of void stacks in real space, without redshift-space distortions. The method uses the expected spherical symmetry of stacked voids to build the shape of the spherical density profile of cosmic voids in real space without any assumption about the cosmological model. The reconstruction algorithm has been tested with both a toy model and a full dark matter simulation. I will present the result for the simulation: the reconstruction of the spherical density profile for a simulated stacked void in real space. I will also present a first application of the algorithm to reconstruct real cosmic void stacks density profiles in real space from the Sloan Digital Sky Survey (Sutter et al. 2012b) and discuss capabilities of the algorithm and possible future improvements. Reconstructed density profiles from real voids are the first step to study the spherically averaged dynamical structure of voids in real space. The reconstruction method does not make any cosmological assumption about the model, thus the density profile reconstruction of stacked voids in real space opens the way to better constrain the value of the Hubble constant and eventually cosmological models and new physics on current and future data sets.

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Dwarf Galaxies are Trying to Kill Cold Dark Matter

12/9/13
James Bullock
(UC Irvine)

The cold dark matter (CDM) cosmological model has been very successful in explaining cosmic structure on large scales and over a vast span of cosmic time, but it has faced ongoing challenges from observations that probe the inner regions of dwarf galaxies in the local universe. Cosmological simulations that incorporate only gravity and collisionless CDM predict central densities that are too high to match constraints from galaxy dynamics. The solution could lie in baryonic physics: gravitational potential fluctuations associated with supernova feedback can lower central densities. However, it is not clear that this solution can work for the faintest galaxies, where basic energetic arguments suggest that feedback alone cannot solve the problem. Alternatively, the anomalous dark matter densities could be evidence of more complex physics in the dark sector itself. For example, elastic scattering from strong dark matter self-interactions can alter predicted halo mass profiles, leading to good agreement with observations across a wide range of galaxy mass. I will discuss ways forward for discriminating between these scenarios.

Indirect Detection of Dark Matter with Gamma Rays

12/10/13
Simona Murgia
(UC Irvine)

Evidence for dark matter is overwhelming. From experimental data we can infer that dark matter constitutes most of the matter in the Universe and that it interacts very weakly, and at least gravitationally, with ordinary matter. However we do not know what it is. Several theoretical models have been proposed that predict the existence of Weakly Interacting Massive Particles (WIMPs) that are excellent dark matter candidates. The existence of WIMPs can be tested indirectly, primarily through their annihilation or decay into photons. In this talk I'll present the latest results on these searches by Fermi LAT.

Neutrinos from GRBs, and the multi-messenger connection

1/21/14
Philipp Baerwald
(Penn State)

The detection of the first ultra-high energy neutrino events inside the IceCube telescope has finally opened neutrinos as a new "window" into the sky. With the neutrino as a new messenger, it is now possible to test astrophysical source models with several different types of messengers. However, to obtain meaningful results from the different messengers, detailed (particle physics) models of the sources are needed. At the example of GRBs, we will first discuss how the neutrino flux predictions are calculated based on gamma-ray observations and how they are used for current neutrino analyses. Then, we will use the particle physics involved to also obtain a prediction of the cosmic ray spectra self-consistently together with the neutrinos. Finally, we will discuss how the combination of neutrino, cosmic ray, and photon data can be used to derive strong constraints on the internal shock fireball model for GRBs and even rule out some of its forms.

The Fermi Bubbles: Possible Nearby Laboratory for AGN Jet Activity

1/24/14
Karen Hsiang-Yi Yang
(U. of Michigan)

One of the most important discoveries of the Fermi Gamma-ray Space Telescope is the detection of two giant bubbles extending 50 degrees above and below the Galactic center (GC). The symmetry about the GC of the Fermi bubbles suggests some episode of energy injection from the GC, possibly related to past jet activity of the central active galactic nuclei (AGN). Thanks to the proximity to the GC, the Fermi Bubbles are excellent laboratories for studying cosmic rays (CRs), Galactic magnetic field, and AGN feedback in general. Using three-dimensional magnetohydrodynamic simulations that include relevant CR physics, I will show how leptonic AGN jets can explain the key characteristics of the Fermi bubbles and the spatially correlated features observed in the X-ray, microwave, and radio wavelengths. I will also discuss how we use our simulations in combination with the multi-wavelength data to obtain constraints on the composition of the Fermi bubbles.

First measurement of pp neutrinos in real time in the Borexino detector

1/28/14
Pablo Mosteiro
(Princeton)

The Sun is fueled by a series of nuclear reactions that produce the energy that makes it shine. Neutrinos (ν) produced by these nuclear reactions exit the Sun and reach Earth within minutes, providing us with key information about what goes on at the core of our star. For decades since the first detection of solar neutrinos in the late 1960's, an apparent deficit in their detection rate was known as the Solar Neutrino Problem. Today, the Mikheyev-Smirnov-Wolfenstein (MSW) effect is the accepted mechanism by which neutrinos oscillate inside the Sun, arriving at Earth as a mixture of νe, νμ and ντ, the latter two of which were invisible to early detectors. Several experiments have now confirmed the observation of neutrino oscillations. These experiments, when their results are combined together, have demonstrated that neutrino oscillations are well described by the Large Mixing Angle (LMA) parameters of the MSW effect.
This talk presents progress towards the first measurement of pp neutrinos in the Borexino detector, which would be the first direct real-time measurement of pp neutrinos independent of other experiments. This would be, furthermore, another validation of the LMA-MSW model of neutrino oscillations. In addition, it would complete the spectroscopy of pp chain neutrinos in Borexino, thus validating the experiment itself and its previous results. We also report on a measurement of neutrons in a dedicated system within the Borexino detector, which resulted in an improved understanding of neutron rates in liquid scintillator detectors at Gran Sasso depths. This result is crucial to the development of novel direct dark matter detection experiments.

Seeing Gravitational Waves: Transients in the Local Universe

2/4/14
Mansi Kasliwal
(Observatories of the Carnegie Institution for Science)

The advent of wide-field synoptic imaging has re-invigorated the venerable field of time domain astronomy. Our framework of optical transients no longer has a wide six-magnitude luminosity "gap" between the brightest novae and faintest supernovae. Multiple new and distinct classes of very rare explosions have been uncovered just in the past few years. I review the surge of excitement (and debate) on the physics of these transients with unprecedented explosion signatures. "Gap transients" represent missing pieces in two fundamental pictures: the fate of massive stars and the evolution of compact binaries. Calcium-rich gap transients may even be the key to solving a long standing abundance problem in the intra-cluster medium. Two classes of gap transients are extremely red, hinting that the infrared dynamic sky is ripe for exploration. I conclude with the next frontier in gap transients --- discovering elusive binary neutron star mergers, a goal which may soon be within reach with coordination between the next generation of synoptic surveys and advanced gravitational wave interferometers. This search may literally be the 21st century gold rush!

Fast, Accurate Predictions of the Galaxy Power Spectrum

2/11/14
Juliana Kwan
(Argonna National Lab)

Two point galaxy clustering statistics are a key observable for large scale structure surveys. Unfortunately, they are very difficult to model accurately within the halo model and perturbation theory. In this talk, I will be presenting a new framework for calculating the galaxy power spectrum, called emulation, which can make predictions accurate to ~3%. Our technique uses a set of fully non-linear galaxy power spectra derived from applying the halo occupation model on a dark matter halo catalogue identified in a LCDM N-body simulation. A Gaussian process model then interpolates over the set of input power spectra. Unlike fitting functions, the cosmic emulation framework can be easily generalised to other problems and I will also describe a number of other projects currently in progress, such as emulating the redshift space power spectrum.

Discovery of Fermi Bubbles and Evidence for Past Activities in the Galactic Center

2/18/14
Meng Su
(KIASR (MIT), ITC (Harvard-Smithsonian Center for Astrophysics))

Analysis of data from the Fermi Gamma-ray Space Telescope revealed a pair of gigantic gamma-ray bubble structures, named the Fermi bubbles, each extending ~10 kpc above and below the Galactic center. I will present new results using five years Fermi-LAT data and multi-wavelength observations of the Fermi bubbles in X-ray, microwave, and radio, including updates from dedicated observations. New observations help us to distinguish hadronic from leptonic origin of the cosmic-ray electrons emitting gamma-ray/microwave emission, and constrain the magnetic field within the Fermi bubbles. I will also show our numerical simulations which demonstrate that the bubble structure could be evidence for past accretion events and outflow from the central supermassive black hole. Furthermore, we recently found evidence for large-scale collimated structure penetrating through the bubbles from the Galactic center from Fermi-LAT data. We have proposed to change the survey strategy of Fermi to increase the exposure at the inner Galaxy by more than a factor of 2. New survey strategy has been initiated since December 2013 and will last for at least one year. I will end up with a discussion of future gamma-ray space missions.

Beyond Dark Energy

2/19/14
Bhuvnesh Jain
(U. Penn)

The discovery that our universe is accelerating poses fascinating challenges for physics and astronomy. Vacuum energy, more generally called dark energy, is a possible explanation for the observed cosmic acceleration. Modifications to Einstein's general relativity are being explored as alternatives to dark energy. I will describe the theoretical motivations and experimental tests of gravity theories and other effects involving dark sector couplings. On large scales, they require a different take on cosmological observations such as gravitational lensing and large-scale structure in the universe. On much smaller scales the new tests of gravity use pulsating stars, rotating disk galaxies and other astronomical phenomena. I will describe how these diverse observations are being used to look "beyond dark energy".

Very High Energy Blazars: A Broadband Perspective

2/25/14
Amy Furniss
(UCSC)

Blazars, a type of active galaxy with a jet pointed toward the observer, are perplexing objects harboring relativistic particle populations with intrinsic characteristics which, despite more than 20 years of investigation, remain an enigma. These sources emit non-thermal radiation and display bright, variable emission at all energies. Blazars are the most commonly detected type of very high energy (VHE; E > 100 GeV) source and can be observed at these energies by imaging atmospheric Cherenkov telescopes such as VERITAS. A foundational understanding of the underlying acceleration mechanisms, particle environment, non-thermal emission and definitive extragalactic distance enable the use of these extraordinary objects to constrain the star formation history of the Universe through the indirect measurement of the extragalactic background light, the accumulated and reprocessed radiation of all starlight produced over the life of the Universe. I will summarize the results from a variety of innovative and complementary multiwavelength observations which can be used to address long-standing questions regarding the underlying acceleration mechanism, the emission environment and constituent particles within VHE blazar jets.

Constraints on the parameter space of axion dark matter

2/26/14
Kfir Blum
(Princeton / IAS)

I will discuss phenomenological constraints on the parameter space of axion dark matter. First, I will review how standard chiral perturbation theory relates the axion mass to the induced neutron electric dipole moment (nEDM). I will argue that this well known relation can only be avoided at the price of fine-tuning, and show that it has significant implications for proposed experimental searches for the oscillating nEDM induced by the background field of axion dark matter. I will then show that, if one is willing to accept this kind of fine-tuning, another constraint comes up by requiring that axion-driven operators in the chiral Lagrangian, that redshift up in the early Universe, do not ruin the success of Big-Bang Nucleosynthesis at z~10^10.

Order out of chaos:
Towards understanding galaxy formation in the cosmological context

3/4/14
Andrey Kravtsov
(Chicago)

Galaxy formation is a complex, hierarchical, highly non-linear process, which involves gravitational collapse of dark matter and baryons, supersonic, highly compressible and turbulent flows of gas, star formation, stellar feedback, as well as heating, cooling, and chemical processes that affect the gas and, indirectly, the stellar and dark matter distributions. Nevertheless, despite the apparent complexity of processes accompanying galaxy formation, galaxies exhibit a number of striking regularities, such as tight correlations between galaxy sizes, masses, luminosities, and internal velocities and surprisingly tight correlations between properties of stars and gas in galaxies and the mass and extent of their parent halos dominated by dark matter. Existence of such correlations indicates that powerful processes operate to bring order out of chaos. Understanding what these processes are and how they operate is not only fascinating scientifically, but is critical for interpreting the avalanche of current and future observations of galaxies across cosmic time. I will describe recent progress in our understanding of how such regularities can arise in a seemingly chaotic and nonlinear process of galaxy formation.

Elizabeth Fernandez

A Multiwavelength Understanding of the Epoch of Reionization

3/11/14
Elizabeth Fernandez
(Groningen)

Up until very recently, the Epoch of Reionization has been largely observationally unexplored . However, with advancements of modern telescopes, we are now able to observe this period of the Universe in multiple ways. While observations are still very challenging due to a host of foreground contaminants, combining observations at multiple wavelengths can lead to a greater understanding of the populations of stars and galaxies at these redshifts. I will describe two of these observables: the Cosmic Infrared Background, which is partially the integrated light from all stars and galaxies at high redshifts, and the 21cm Background, which results from emission from neutral gas. These observables, when paired with theory and simulations, can tell us about some of the first stars and galaxies that formed within our Universe.

Plot

"Light WIMPs" in direct dark matter detection

3/18/14
Graciela Gelmini
(UCLA)

Four direct dark matter detection experiments, DAMA, CoGeNT, CRESST and CDMS-II-Si, find potential signals of "Light WIMPs" (Weakly Interacting Massive Particles with mass 10 GeV or lighter) while several other experiments, CDMS-II-Ge, CDMSlite, SuperCDMS, XEONON10, XENON100, LUX..., do not find any. Are all or some the positive and negative signals compatible with each other? I will review the experimental situation and compare the data for different particle candidates in a dark halo model dependent and in a dark halo model independent manner.

Using Millions of SDSS Halo Stars to Robustly Measure the Shape of the Milky Way's Dark Matter Halo

3/25/14
Sarah Loebman
(Michigan)

I will present detailed evidence from the Sloan Digital Sky Survey (SDSS) for the presence of a dark matter halo within Milky Way (MW). Using the number density distribution and kinematics of SDSS halo stars, my collaborators and I probe the dark matter distribution to heliocentric distances exceeding ~10 kpc and galactocentric distances exceeding ~20 kpc. Our analysis utilizes Jeans equations to generate two-dimensional acceleration maps throughout the volume; this approach is thoroughly tested on a cosmologically derived N-body+SPH simulation of a MW-like galaxy. We show that the known accelerations (gradients of the gravitational potential) can be successfully recovered in such a realistic system. The SDSS observations reveal that, in Newtonian framework, the implied gravitational potential cannot be explained by visible matter alone: the gravitational force experienced by stars at galactocentric distances of ~20 kpc is as much as three times stronger than what can be attributed to purely visible matter. Leveraging the baryonic gravitational potential derived by Bovy & Rix (2013), we show that the SDSS halo stars also provide a strong constraint on the shape of the dark matter halo potential. Within galactocentric distances of ~20 kpc, the dark matter halo potential is well described as an oblate halo with axis ratio q_DM=0.7+/-0.1. Thanks to precise two-dimensional measurements of acceleration for halo stars, we can reject MOND model as an explanation of the observed behavior, irrespective of the details in assumed in the interpolating function and the value of characteristic acceleration. In the era of Gaia and LSST, these techniques can be used to map the MW dark matter halo with a much better fidelity, and to a much larger galactocentric radius.

Review of the proton radius puzzle

3/27/14
Maxim Pospelov
(Victoria, Perimeter)

Recent measurements of the Lamb shift in the muonic hydrogen and deuterium revealed a puzzling discrepancy with similar measurements in e-p systems. This is often presented as a difference in the value for the proton charge radius. The origin of the discrepancy is not known, and in my talk I will cover possible scenarios for its resolution: an experimental error, "unusual" QCD effects, or new MeV-scale forces. For the latter, I describe a new idea for searches of MeV-scale force carriers using underground accelerators.

The Physics of Gas Sloshing in the Cores of Galaxy Clusters

4/1/14
John ZuHone
(NASA-Goddard)

Many X-ray observations of relaxed galaxy clusters reveal the presence of sharp, spiral-shaped discontinuities in the surface brightness of the X-ray emitting gas. Spectral analysis of these features shows that the colder gas is on the brighter side, hence they have been dubbed "cold fronts." These features arise naturally in simulations from the cool-core gas "sloshing" in the gravitational potential. Their sharpness and stability has important implications for the microphysics of the ICM. The sloshing motions may have other effects, such as contributing to the heating of the cluster core and the acceleration of relativistic particles. I will present simulations of gas sloshing in clusters, explain their formation and evolution, and discuss the implications for the physics of the ICM, including fresh results on heat conduction, viscosity, and radio mini-halos. I will also briefly discuss yt, an emerging software toolkit for analyzing astrophysical data from simulations and other datasets.

Statistically probing the merger history of the Milky Way

4/8/14
Facundo Gomez
(Michigan State)

Despite a wealth of observational information that is currently available, the details of the formation of our own Galaxy remain a puzzle. Thanks to the latest generation of stellar surveys it is now possible to study in detail how the Milky Way has evolved to become the galaxy we currently observe During the first part of this talk I will discuss how semi-analytic models of Galaxy formation, coupled to cosmological N-body simulations, could allow us to constrain the Milky Way merger history. Statistical model emulators are used to efficiently explore the multi-dimensional input parameter space of our model. We search for the sets of input parameters that can best reproduce the cumulative Luminosity Function (cLF) of satellite galaxies. Our results indicate that the determination of "best-fit" parameters is highly susceptible to the particular merger history of the Milky Way-like host. When comparing the resulting best-fitting models against independent sets of observational data, we find that only one of these models was able to simultaneously reproduce the stellar halo mass within 40 kpc of the Galactic center and the cLF. On the basis of this analysis it is possible to disregard certain models, and their corresponding merger histories, as good representations of the underlying merger history of the Milky Way. During the second part of this talk I will discuss about the perturbations that a minor merger event may induce in the phase-space distribution of Solar Neighborhood stars. In particular, I will show how the interaction between the Milky Way disc and the Sagittarius dwarf galaxy could qualitatively explain some of the radial and vertical perturbations identified in current observational data sets.

Cosmology with the Baryon Oscillation Spectroscopic Survey (BOSS)

4/15/14
Florian Beutler
(LBNL)

I will present the results of the BOSS-DR11 analysis which we published 4 months ago. I will also present measurements of the growth of structure through redshift-space distortions using the power spectrum multipoles. Such a measurement can be used to test General Relativity. Our measurements are in some tension with the expectation of LCDM and I will suggest ways in which this tension can be alleviated.

Constraints on Dark Matter from Merging Galaxy Clusters

4/22/14
Doug Clowe
(Ohio University)

Over the past decade, merging galaxy clusters have become one of the primary sources of data for constraining properties of dark matter particles as well as the force law of gravity on Mpc scales. Using the Bullet Cluster, I will demonstrate how merging clusters prove that dark matter makes up the majority of the mass of their systems independent of assumptions regarding the nature of the force law of gravity and place constraints on the self-interaction cross-section of dark matter. I will review the dozen merging clusters that have been studied since the Bullet Cluster, and discuss whether any of them show serious departures from a light-traces-mass paradigm that would cause significant problems for a LCDM universe.

Interpretation of standard problems associated with Milky Way dwarf spheroidals

4/29/14
Louis Strigari
(Indiana U.)

Improvements in theory and observations have put a new spin on the classical problems involving Milky Way dwarf spheroidals, and dwarf galaxies in general. In this talk, I will discuss what information can robustly be extracted from these observations, and how this information can be connected to the large scale cosmological model. I will close by discussing how this field will progress in the era of 30m class telescopes and with forthcoming galaxy surveys.

High redshift starburst galaxies revealed by SPT, ALMA, and gravitational lensing

5/6/14
Joaquin Vieira
(Illinois, Urbana-Champaign)

The South Pole Telescope (SPT) has systematically identified a large number of high-redshift strongly gravitationally lensed starburst galaxies in a 2500 square degree cosmological survey of the millimeter (mm) sky. With ALMA, we have performed an unbiased spectroscopic redshift survey with these sources and determined that roughly 40% lie at z>4. Two sources are at z=5.7, placing them among the highest redshift starbursts known, and demonstrating that large reservoirs of molecular gas and dust can be present in massive galaxies near the end of the epoch of cosmic reionization. These sources were additionally targeted with high resolution imaging with ALMA, unambiguously demonstrating them to be strongly gravitationally lensed by foreground structure. We are undertaking a comprehensive and systematic followup campaign to use these ``cosmic magnifying glasses'' to study the infrared background in unprecedented detail, inform the condition of the interstellar medium in starburst galaxies at high redshift, and place limits on dark matter substructure. I will discuss the scientific context and potential for these strongly lensed starburst galaxies, give an overview of our team's extensive followup efforts, and describe our latest science results.

Microlensing techniques: revealing the "black box"

5/27/14
Ana Mosquera

You know that microlensing techniques are powerful. You know that our group and collaborators have used them to set by the first time limits on quasar's X-ray emitting regions. And you know that currently you can only rely upon us to study the inner structure of AGNs. But, how does the microlesing machinery actually works? Under which assumptions do we fit and analyze the data? And why is our technique so robust? In my talk I'll answer to these questions following Mosquera et al. 2013.

Magnetic Deflections of Ultra-High Energy Cosmic Rays

5/27/14
Michael Sutherland

The nature of cosmic rays are mysterious even more than a century after their discovery. At the highest energies ($E > 10^{18}$ eV), their composition and sources are unknown. Deflection in cosmic magnetic fields, even at these ultra-high energies, complicates source identification due to a direct dependence on the composition as well as uncertainties in the magnetic fields. For a nearby source, for example Centaurus A (Cen A), deflection from the extragalactic magnetic field is minimized. This allows for deflection studies of the Galactic magnetic field (GMF), which itself is capable of significantly altering UHECR trajectories. I will highlight a study of simulated UHECR trajectories from Cen A to Earth for a range of rigidities, allowing for primaries as heavy as Fe nuclei with energies exceeding 50 EeV. The Galactic magnetic field is modeled using the recent work of Jansson and Farrar which fitted its parameters from extragalactic Faraday rotation measures and WMAP7 synchrotron emission maps. This model also includes parameters for a detailed turbulent component. Aspects of the arrival direction distributions are examined for dependencies on rigidity and properties of turbulent field realizations.

Galaxy intrinsic alignments: systematic nuisance or powerful probe?

6/3/14
Jonathan Blazek

The shapes and orientations of galaxies arise from complex processes on comparatively small scales. In the context of weak gravitational lensing measurements, large-scale correlations between these shapes, known as "intrinsic alignments" (IA), constitute the most significant astrophysical source of uncertainty and have the potential to degrade cosmological constraints. If sufficiently understood, however, IA can probe the physics of the formation and evolution of galaxies and their surrounding dark matter halos. IA may also provide a valuable tracer of large-scale structure. In this talk, I will outline why understanding IA is critical for current and future weak lensing surveys, including DES and LSST. I will describe recent and ongoing work in which we use both analytic modeling and observational data to make significant progress towards this goal.

Quasars and their absorption lines: a legacy survey of the high redshift universe with X-shooter

6/3/14
Kelly Denney

Utilizing the X-shooter spectrograph on the VLT, we have obtained spectra of 100 z>3.5 QSOs with high S/N (95% of the reduced spectra have S/N>20 and ~50% have S/N>30). X-shooter is a unique, 3-arm echelle spectrograph that covers wavelengths from the UV cutoff ~3000A through K-band (2.48 microns) at R~6,000. This Large Programme represents the first major spectroscopic QSO survey in the rest-frame UV and optical at z>3.5. I will present our data and science goals, though given the time allotted, I will only be able to discuss in more detail some of our plans for this exquisite data set, which encompass (1) measurement of the matter power spectrum with the Ly-alpha forest at high redshift, including an independent measurement of cosmological parameters with a joint analysis of these and the Planck publicly released data; (2) determination of the incidence of MgII absorbers at z > 2.5 with unprecedented sensitivity to test predictions from the cosmic star formation rate; (3) investigation of the physical environments of the quasars, including, e.g., accurate measurements of black-hole masses, luminosities and metal abundances in a homogeneous sample; and (4) measurement of the universe's opacity at the Lyman limit and constraint of the UV background via the proximity effect.

AGN-STORM - Space Telescope and Optical Reverberation Mapping of NGC 5548

6/10/14
Gisela DeRosa

Active Galactic Nuclei are the spectacular manifestation of accreting black holes and can tell us many things about their central powering engines. Reverberation mapping is a powerful technique to study the region near the supermassive black holes, allowing a full geometric and kinematic modeling of the broad line region gas through the study of variations of the emission line profiles. After a brief review of reverberation mapping methods, I will focus on AGN-STORM, a program centered on 180 daily HST observations designed to study in unprecedented details the broad line region in one AGN: NGC 5548. I will describe the observing strategy, the challenges and the aims of this ambitious project and present preliminary results.

Detecting absorption signatures of warm / hot gas circum-galactic gas in COS archival data

6/10/14
Stephan Frank

A large fraction of the baryons at the low redshift universe (z=1, and below) has thus far escaped our heroic detection efforts. Simulations predict that part of these "missing" baryons may be located in areas of the temperature-density parameter space that would produce weak UV absorption features when seen against bright background sources like QSOs. Here, I am going to report on our ongoing project to detect such a weak signature of this gas, focusing on a specific transition (NeVIII). Instead of presenting polished results, however, I will focus on the method itself we have specifically developed for this prupose ('agnostic stacking'), but also highlighting its broader applicability for similar searches.

Model Independent Measurements of Angular Power Spectra

6/17/14
Sheldon Campbell

Spatial fluctuations of astrophysical signals are a powerful probe of source distributions, radiation production mechanisms, and propagation effects. The precision of measuring angular power spectra is currently estimated as a combination of shot noise, instrument systematics, and cosmic variance. We show that an important contribution, dependent on the finite statistics of the experiment, has been neglected. These new results allow for improved estimates of sensitivities to angular power by statistics-limited observations, such as for high-energy gamma rays.

First exoplanet similar to Uranus

6/17/14
Radek Poleski

We know exoplanets similar to both inner rocky planets of Solar System as well as Jupiter and Saturn. However, the long orbital periods of Uranus and Neptune make their analogs inaccessible to methods that depend on periodic phenomenon i.e. radial velocities and transits. Also direct imaging is not sensitive enough. I present the first discovery of extrasolar planet that has orbit and mass similar to Uranus using gravitational microlensing method. Moreover, the host star has a relatively nearby stellar or brown dwarf companion. All the basic properties of the lens triple system can be understood without detail modeling.

Dynamical Modeling of the Broad Line Region in AGNs with Reverberation
Mapping Data

6/24/14
Kate Grier

Both theoretical and observational evidence suggests that galaxies and their central supermassive black holes are connected. In order to understand these connections, we must have accurate measurements of supermassive black hole masses in objects across the observable universe. All black hole mass measurements in distant galaxies are made using emission lines in active galactic nuclei (AGN) -- however, the unknown conditions within the broad line-emitting region could be a source of serious systematic errors in black hole mass measurements in these objects. Reverberation mapping methods have the capability of both yielding black hole mass easurements as well as information about the broad line region itself. I will discuss the use of dynamical modeling techniques with reverberation mapping data to probe the geometry and kinematics of the broad line region in active galactic nuclei to help better constrain black hole mass estimates in these galaxies and understand the physics of the BLR, highlighting preliminary results using data from a 2010 reverberation campaign carried out here at OSU.

Understanding the Detector Background for Astrophysical MeV
Neutrino Detection

6/24/14
Shirley Li

Background rejections are crucial for MeV neutrino detection. When muons travel through matter, their energy losses lead to nuclear breakup (“spallation”) processes. Subsequent beta decays can lead to detector backgrounds that mimic neutrino signals, and isotopes with long lifetimes are especially difficult to cut. In a recent paper from Super-Kamiokande collaboration, a correlation between the spallation event position and a peak in the prior muon Cherenkov light profile was found. We calculate the rates of isotopes produced by muons and their secondaries in Super-Kamiokande and study the properties of electromagnetic showers induced by muons. A better theoretical understanding of these processes will help in developing new techniques to reduce detector backgrounds.

Answers from the void

7/1/14
Paul Sutter

Voids are the large, underdense regions in the cosmic web, and they are potentially powerful cosmological probes due to their intimate connection to the growth of structure, their domination by dark energy, and their relative lack of systematics. I will present our latest work to identify voids in galaxy redshift surveys, our efforts to understand their fundamental nature and their connection to dark matter underdensities, and an overview of many diverse cosmological applications, including gravitational lensing, the ISW effect, and the Alcock-Paczynski effect.

Clustering, Proximity, and Balrog

7/1/14
Eric Suchyta

I will present work in progress about what happens to galaxy clustering when the influence of proximity effects in the data are included. I will touch on a new software package we have developed which is directly related to problem at hand. I will demonstrate in simple terms what is difficult about the problem and what the answer must look like.

Fishing for the FIR Line Deficit in the Local Swimming Hole: Heating and Cooling in the ISM

7/8/14
Kevin Croxall

The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. The principal mechanisms responsible for the heating and cooling of this gas are thought to be the injection of photoelectrons from dust and far-infrared line emission, respectively. In standard practice, we express the efficiency of the photoelectric effect as the ratio of the strong [CII] cooling line emission to thermal dust emission, [CII]/TIR. As the average temperature of dust grains increases a deficit appears in the ratio of [CII]/TIR, according to studies of the global properties of galaxies. While several solutions to this occurrence have been suggested, its cause has not been clear. However, galaxies host a complex ISM, that is most certainly inhomogeneous. Deeper understanding of this deficit requires observations with better spatial resolution to disentangle environments with different radiation fields. Using data from the Herschel space observat ory we investigate the [CII] deficit in nearby galaxies.

Testing the wedge effect on future 21cm BAO surveys

7/8/14
Hee-Jong Seo

Baryon acoustic oscillations (BAO) provide a robust standard ruler with which to measure the acceleration of the Universe. The BAO feature has so far been detected in optical galaxy/qso surveys. Intensity mapping of neutral hydrogen emission with a ground-based radio telescope provides another promising window for measuring BAO at redshifts of order unity for relatively low cost. Although very promising in terms of performance per cost, the major challenge for this method is the severe foreground contamination. I will discuss the effect of the foregrounds on 21cm surveys when they are not removed properly.

Unorthodox weak-lensing applications in DES

7/15/14
Peter Melchior

The Dark Energy Survey (DES) will soon start the second season of observations. I'll review the current state of the survey and summarize the efforts to control and improve the quality of observations and data processing. I will then discuss ideas how to exploit the existing data for weak-lensing purposes in several ways other than cosmic shear.

An Ultra-high Energy Neutrino Search with the ARA Testbed

7/22/14
Carl Pfendner

The Askaryan Radio Array (ARA) is an ultra-high energy (UHE) cosmic neutrino detector located at the South Pole. The cosmic ray flux cut off above primary energies of 10^19.5 eV leads us to expect a UHE neutrino flux due to the GZK effect. The detection of these UHE cosmic neutrinos will add to the understanding of the sources and physics of UHE cosmic rays. ARA uses the radio Cherenkov technique to search for UHE neutrinos by deploying radio frequency (RF) antennas at 200m depth in the Antarctic ice and searching for impulsive RF signals. A prototype ARA Testbed station was deployed in the 2010-2011 season and the first design-level ARA stations were deployed in the 2011-2012 and 2012-2013 seasons. I will present the results of one of the first neutrino searches with 2011-2012 ARA Testbed data.

Hot galactic winds constrained by the X-ray luminosities of galaxies and ram pressure acceleration of cold clouds

7/22/14
Dong Zhang

 

Galactic superwinds may be driven by very hot outflows generated by overlapping supernovae within the host galaxy. We use the Chevalier & Clegg (CC85) wind model and the observed correlation between X-ray luminosities of galaxies and their SFRs to constrain the mass loss rates across a wide range of star formation rates (SFRs), from dwarf starbursts to ultra-luminous infrared galaxies. We show that for fixed thermalization efficiency and mass loading rate, the X-ray luminosity of the hot wind scales as Lx ~ SFR2, significantly steeper than is observed for star-forming galaxies: Lx ~ SFR. Using this difference we constrain the mass-loading and thermalization efficiency of hot galactic winds. For reasonable values of the thermalization efficiency (<~ 1) and for SFR >~ 10 M_sun/yr we find that \dot{M}hot/SFR <~ 1, significantly lower than required by integrated constraints on the efficiency of stellar feedback in galaxies, and potentially too low to explain observations of winds from rapidly star-forming galaxies. Moreover, we highlight that the CC85-like hot wind is unlikely the mechanism in accelerating neutral cold outflows in most starbursts observed by Na D absorption surveys, expect for some local dwarf starbursts.

Recent progress on Magnification in the Dark Energy Survey

7/31/14
Eric Huff

 

Magnification is shear's neglected cousin, and by ignoring this lensing measurements ignore half of their potential signal. There are good reasons for this, but recent progress on magnification with Dark Energy Survey data holds out the prospect of magnification's achieving parity with shear. In this talk, I will describe the hybrid image simulations that make this feasible, and show preliminary magnification results using DES data.

Gyrochronology in the Kepler Era: What Can Stellar Rotation Do for You?

7/29/14
Jennifer van Saders

 

Cool, single main sequence stars have rotation periods that increase as they age. The technique of gyrochronology uses the observed relationship between rotation period, stellar color, and age to date old field stars based on two key assumptions: 1) that all targets can be treated as single main sequence stars that spin down as a function of time, and 2) that the relations can be calibrated on systems of solar age and younger and extrapolated to old stars, where data has traditionally been sparse. With the recent availability of space-based photometry that provides both rotation periods (from stellar spot modulation) and independent ages (from asteroseismology), we are in a unique position to test and better calibrate rotation as a tool. I focus, in particular, on how an understanding of observational selection effects and behavior of rotation across all stellar types is critical for the calibration and interpretation of gyrochronological ages.

Cross-correlating Planck, SPT, DES, Fermi and low-redshift galaxy surveys

7/31/14
Aurelien Benoit-Levy

 

By deflecting the trajectories of the CMB photon from the last scattering surface, gravitational lensing imprints statistical signatures of the matter distribution in the observed temperature and polarization anisotropies of the CMB. Extracting this signature permits the reconstruction of the lensing potential, a powerful probe of the matter distribution. Matter distribution can also be probed by galaxy surveys thus providing additional information that can be correlated with the CMB lensing potential. In this talk I will present some aspects of these cross-correlations focusing on the complementary of DES and Planck/SPT. I will also present some recent work that focuses on the correlation of the gamma ray sky observed by the Fermi satellite and catalogues of nearby galaxies.

Understanding the Magnetic Variability of M and L dwarfs

8/5/14
Sarah Schmidt

 

M and early-L dwarfs are often active, revealing the presence of magnetic fields through both quasi-static emission from their chromospheres and coronae in addition to dramatic flares. Even the quasi-static emission exhibited by these low mass stars is intrinsically variable on timescales ranging from minutes to possibly even decades. I will briefly discuss current and future work to understand the magnetic variability of M and L dwarfs through photometric surveys for flares and spectroscopic monitoring for variations in the Halpha emission lines.

Improved limits on sterile neutrino dark matter by Fermi-GBM

8/5/14
Kenny Ng

 

Sterile neutrinos with mass in the keV range are a well motivated dark matter candidate. Interestingly, these cannot be completely stable, though the lifetimes are very long. The decays produce an X-ray line that provides a distinctive signature. Stringent limits were set using Chandra, XMM-Newton, and INTEGRAL. However, there is a gap in sensitivity for the mass range 20 to 40 keV (with line energy 10 to 20 keV), because this is outside the sensitivity range of the fore-mentioned missions. For the first time, we show that it is possible to use Fermi Gamma-ray Burst Monitor (GBM) data to search for such lines in this gap. Our preliminary result show that we can improve the limit on sterile neutrino decay rate by about an order of magnitude.

Cosmic Rays and Neutrinos as Complementary Probes of Ultra-High Energy Astrophysics

8/12/14
Nathan Griffith

 

Ultra-high energy cosmic ray and neutrino spectra provide us with a complementary set of information that can be used to uncover a variety of information about ultra-high energy phenomena. This work uses fits to the Pierre Auger Observatory's 2013 data to generate neutrino spectra. Then, looking through the lens of next generation neutrino detectors (EVA, ARA), the ultra-high energy parameters of source distribution and source spectrum are inspected.

An All-Sky, Multi-wavelength Astronomy Computational Engine

8/12/14
Demitri Muna

 

Astronomy produces extremely large data sets from ground-based telescopes, space missions, and simulation. The problem is that no one institution can host all of this data, let alone have the resources to properly manage it. The result is that applying analyses against full data sets across the wide range of wavelengths available is either beyond the resources of most astronomers or currently impossible. Simply having an extremely large volume of data available in one place is not sufficient; one must be able to make valid, rigorous, scientific comparisons across very different data sets from very different instrumentation. This talk will describe a framework of distributed data and distributed computation for astronomers.

Elizabeth Fernandez

From Nexus to Hopf: on the structure and dynamics of the Cosmic Web

8/19/14
Rien van de Weijgaert
(Kapteyn Institute, University of Groningen)

 

The Cosmic Web is the fundamental spatial organization of matter on scales of a few up to a hundred Megaparsec, scales at which the Universe still resides in a state of moderate dynamical evolution. galaxies, intergalactic gas and dark matter exist in a wispy weblike spatial arrangement consisting of dense compact clusters, elongated filaments, and sheetlike walls, amidst large near-empty void regions. This seminar will describe recent work on the structure and dynamics of the Cosmic Web. For the analysis of its complex and multiscale structural pattern, we invoke concepts from computational topology and computational geometry. We apply the explicit multi-scale -- parameter-free and scale-free -- Nexus/MMF Multiscale Morphology formalism to dissect the cosmic mass distribution into clusters, filaments, walls and voids. This results in a systematic study of the evolving size and volume distribution of these structural components. Subsequently, we assess the mass and halo distribution in the filaments and walls, and follow their evolution. To study the dynamical evolution of the cosmic web, we have developed an updated adhesion model of cosmic structure formation based on Voronoi and Delaunay tessellations. With this we can systematically follow the outline of the emerging cosmic web and its morphological components. This provides a systematic assessment of the sensitivity of the cosmic web to different cosmologies and/or as a function of power spectrum. We conclude with a short discussion of the detection of galaxy spin alignments with the filaments in which galaxies are embedded, the most direct manifestation of the influence of filaments on the properties of galaxies.

Tova Yoast-Hull

Cosmic Ray Populations in Three Starbursting Galaxies

8/26/14
Tova Yoast-Hull
(Wisconsin)

 

M82, NGC 253, and Arp 220 are often associated with each other due to similarities in the intense starburst environments contained within each galaxy. Dense concentrations of young massive stars, strong magnetic fields, and high radiation fields characterize their starburst nuclei. Additionally, both M82 and NGC 253 have been detected in gamma-rays with Fermi. Despite their similarities, the interstellar medium and effects of galactic winds differ in these galaxies. However, these distinctions are vital to understanding the role of cosmic ray interactions and the observed radio and gamma-ray spectra from each galaxy. I will discuss results of my single-zone models of the cosmic ray populationsof the starburst nuclei and their implications for future gamma-ray and neutrino observations.

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