KICP Friday Noon Seminars
KICP Seminars - Usually Fridays, 12 PM, LASR conference room, unless otherwise specified.

Past KICP Seminars
DateTalk TitleSpeaker
May 29, 2015Cosmic Flows: cosmology and astrophysics from galaxy velocitiesSimone Ferraro, Princeton University
May 22, 2015Probing the environments of supermassive black-hole binaries with pulsar timing arraysSean McWilliams, West Virginia University
May 15, 2015Re-Examining Astrophysical Constraints on the Dark Matter ModelAlyson Brooks, Rutgers University
May 8, 2015Probing New Physics Beyond the Standard Model with CosmologyCora Dvorkin, Harvard University
May 1, 2015Partially Massless Charges and MonopolesRachel A Rosen, Columbia University
April 24, 2015Gamma-rays from type Ia supernova SN2014JEugene Churazov, Max Planck Institute for Astrophysics
April 17, 2015Cosmological results from Planck 2015Silvia Galli, University of Chicago
April 3, 2015Measuring Dark Energy with CHIMELaura Newburgh, Dunlap Institute, University of Toronto
March 20, 2015Near-IR Background Fluctuations Results from the Cosmic Infrared Background ExperimentMichael Zemcov, California Institute of Technology
March 6, 2015Indirect Detection of Dark Matter with Gamma RaysSimona Murgia, UC Irvine
February 27, 2015What's Next for Cosmology with Type Ia SupernovaeDaniel Scolnic, University of Chicago
February 20, 2015Consistency Relations for Large Scale StructureMarko Simonovic, IAS, Princeton
February 13, 2015Joint Analysis of BICEP2, Keck Array, and PlanckColin Bischoff, Harvard-Smithsonian Center for Astrophysics
February 6, 2015Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''Tobias Marriage, Johns Hopkins University
January 30, 2015Decisively Testing Sub-GeV Dark Matter Through the Vector PortalGordan Krnjaic, Perimeter Institute for Theoretical Physics
January 23, 2015Observing the Assembly of Dark Matter and Baryons in Massive GalaxiesAndrew B Newman, Carnegie Observatories
January 16, 2015Dark matter halos as particle collidersSean Tulin, York University
January 9, 2015First results from the High Altitude Water Cherenkov ObservatoryMiguel A. Mostafa, Penn State University

First results from the High Altitude Water Cherenkov Observatory
January 9, 2015 | LASR conference room | 12:00 PM
Miguel A. Mostafa, Penn State University

Dark matter halos as particle colliders
January 16, 2015 | LASR Conference Room | 12:00 PM
Sean Tulin, York University

Astrophysical observations of structure can be used to study the non-gravitational particle interactions of dark matter. I discuss small scale structure anomalies for cold dark matter and their possible implications for dark matter physics. New results on cluster scales provide a new important handle for constraining dark matter's particle interactions.

Observing the Assembly of Dark Matter and Baryons in Massive Galaxies
January 23, 2015 | LASR Conference Room | 12:00 PM
Andrew B Newman, Carnegie Observatories

Massive galaxies are central to many pressing questions in galaxy formation and cosmology. Observations of the evolving distributions of baryons and dark matter within massive galaxies can constrain the astrophysical processes that drive their formation and growth. In the first part of the talk, I will present results from a program aimed at understanding the assembly of the stellar halos of massive galaxies over the last 10 Gyr. Beginning as compact "nuggets" at z~2, these galaxies undergo a remarkably rapid period of growth. By combining HST imaging with unique spectroscopic surveys conducted on large telescopes, I will show how measurements of the sizes, stellar populations, internal dynamics, and satellite systems of z>1 massive galaxies have provided new insights into their remarkable growth. In the second part, I will turn to the dark matter distribution at the centers of massive galaxies and clusters. Through a synthesis of multiple observational probes, including strong lensing, weak lensing, and stellar dynamics, I have constrained the slope of the inner dark matter density profile. Surprisingly, this analysis implies a slope that is shallower than the universal CDM profile in the central ~30 kpc of massive clusters. I will review attempts to explain this finding in recent numerical simulations as a consequence of the "back-reaction" of baryons on their host halos, or alternatively as a possible probe of dark matter microphysics.

Decisively Testing Sub-GeV Dark Matter Through the Vector Portal
January 30, 2015 | LASR Conference Room | 12:00 PM
Gordan Krnjaic, Perimeter Institute for Theoretical Physics

In a broad class of consistent models, MeV to few-GeV dark matter (DM) interacts with ordinary matter through kinetically-mixed vector mediators ("dark photons"). We outline a two-pronged experimental program to decisively test nearly all such scenarios. The first prong involves placing a suitable meter-scale detector downstream of an existing electron beam-dump to directly observe DM produced in electron-nucleus collisions. Once produced, the DM scatters in the detector and induces highly-energetic electron or nuclear recoils. This approach can explore a well-motivated and otherwise inaccessible region of DM parameter space with sensitivity several orders of magnitude beyond existing direct detection and LHC constraints. This approach would also probe invisibly decaying dark-photons down to kinetic mixing of epsilon ~ 10^{-4}, including the range of parameters relevant for explaining the (g-2)_{mu} discrepancy. The second, more powerful prong of this discovery program relies entirely on the distinctive kinematics of the DM production in electron-nucleus interactions. In this setup, individual electrons are fired through a thin target adjacent to a tracker and calorimeter. If DM particles are produced as the electron passes through the target, they carry away a large fraction of the incident electron's electron energy. Surprisingly, with suitable trigger and kinematic requirements, such events serve as powerful probes of DM-electron interactions and can explore kinetic mixing parameters down to epsilon ~ 10^{-7}, which covers nearly all the parameter space consistent with a thermal relic abundance, thereby testing all vector-portal models that have ever achieved thermal equilibrium with the Standard Model.

Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''
February 6, 2015 | LASR Conference Room | 12:00 PM
Tobias Marriage, Johns Hopkins University

Part 1: Evidence is mounting that Active Galactic Nuclei (AGN) are responsible for the lack of star-formation in the most massive galaxies. Attention has been drawn to the role of energetic radio-mode feedback from AGN in heating the gas around massive halos and preventing star-formation. I will present the first measurement using the Sunyaev-Zel'dovich (SZ) effect of the pressure of the gas around radio-loud AGN.

Part 2: The Cosmology Large Angular Scale Surveyor (CLASS) is a project to measure the imprint of gravitational waves from inflation in the polarization of the cosmic microwave background. I will present an overview of the CLASS strategy for measuring the E-modes and B-modes from both recombination and reionization and give an update on the project status.

Joint Analysis of BICEP2, Keck Array, and Planck
February 13, 2015 | LASR conference room | 12:00 PM
Colin Bischoff, Harvard-Smithsonian Center for Astrophysics

BICEP2, a CMB polarization experiment that operated at the South Pole from 2010-2012, reported a detection of B-mode polarization at degree angular scales in March of last year. While this result was initially interpreted as evidence for primordial gravitational waves from inflation, new data from the Planck satellite has shown that polarized emission from Galactic dust is brighter than what was assumed. I will report on the just-released joint analysis of data from BICEP2, the Keck Array (successor to BICEP2 at the South Pole), and Planck. I will also discuss the prospects for improving this measurement in the near future with data at 100 and 220 GHz from Keck Array and BICEP3.

Consistency Relations for Large Scale Structure
February 20, 2015 | LASR Conference Room | 12:00 PM
Marko Simonovic, IAS, Princeton

Consistency relations for LSS are general, non-perturbative statements about correlation functions of density perturbations. They relate the squeezed limit of an (n+1)-point function with the corresponding n-point function. I this talk I will review the derivation of the consistency relations in the non-relativistic limit and full GR, and show how these results can be applied in constraining the Equivalence Principle on cosmological scales and the BAO reconstruction.

What's Next for Cosmology with Type Ia Supernovae
February 27, 2015 | LASR Conference Room | 12:00 PM
Daniel Scolnic, University of Chicago

We are currently in the midst of a huge explosion in the number of Type Ia Supernovae we've found to better determine cosmological parameters. With the release of Pan-STARRs data, the start of the Dark Energy Survey, and multiple surveys at both low and high-redshift, our statistics will soon improve by an order of magnitude. At the same time, analysis of the systematic uncertainties of these large samples has never been more difficult - there are still questions of how to understand the relationship between supernovae and their host galaxies, and how well we can calibrate all the various samples we wish to join. During this talk, I will give a tour of the current state of cosmology with Type Ia Supernovae and how things will look different within this next year and next few years. I will show some initial results from the new Pan-STARRs cosmology analysis. I will give an update on the current status of the supernova analysis with the Dark Energy Survey. I will also discuss a new low-z survey called the Foundation survey and discuss how recent findings may affect the local H_0 measurements. I will also discuss results from measurements of high-z SNe with the Hubble Space Telescope, and explain how the significance of these measurements depends on the parameterization of the equation-of-state w(z). This understanding is crucial for planning of the WFIRST mission in the next ten years, and I will present first simulations for this survey and how we can assess various strategies.
There is an incredible amount of supernova data on its way, and I hope to give a sense of what to expect.

Indirect Detection of Dark Matter with Gamma Rays
March 6, 2015 | LASR Conference Room | 12:00 PM
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.

Near-IR Background Fluctuations Results from the Cosmic Infrared Background Experiment
March 20, 2015 | LASR Conference Room | 12:00 PM
Michael Zemcov, California Institute of Technology

The galaxies responsible for the reionization of the intergalactic medium at z > 6 produce fluctuations in the diffuse near-infrared background that can be detected by an instrument sufficiently sensitive to surface brightness fluctuations. The Cosmic Infrared Background Experiment (CIBER) was designed to make this measurement, and over the course of four sounding rocket flights has successfully measured the amplitude of the near-IR background fluctuations on arcminute scales. We detect an electromagnetic spectrum that is nearly Rayleigh-Jeans with an indication of a turn over at 1.1 microns, a spectrum that is significantly bluer than the integrated light from galaxies. These fluctuations have been interpreted as arising from intra-halo light from old, low mass stars residing in dwarf galaxies or dissociated from their parent galaxies during merging events over the history of the Universe. This population has implications for large scale structure formation, implying the existence of a previously undetected population that may account for an appreciable fraction of the missing baryons in the Universe.

Measuring Dark Energy with CHIME
April 3, 2015 | LASR Conference Room | 12:00 PM
Laura Newburgh, Dunlap Institute, University of Toronto

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a new radio transit interferometer currently being built at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC, Canada. We will use the 21cm emission line of neutral hydrogen to map baryon acoustic oscillations between 400-800MHz across 3/4 of the sky. These measurements will yield sensitive constraints on the dark energy equation of state between redshifts 0.8 -- 2.5, a fascinating but poorly probed era corresponding to when dark energy began to impact the expansion history of the Universe. I will describe the CHIME instrument, the analysis challenges, the calibration requirements, and current status.

Cosmological results from Planck 2015
April 17, 2015 | LASR Conference Room | 12:00 PM
Silvia Galli, University of Chicago

Planck is an ESA satellite aimed at the observation of the Cosmic Microwave Background. In 2013, the Planck collaboration has released the first results on cosmology based on temperature only data from ~15 months of observations. This year, we released the second round of cosmological results based on full mission data (~30+ months) both in temperature and, for the first time, in polarization. In this talk, I will review a few of the main cosmological results of this year release, showing the main changes with respect to the 2013 release. I will highlight the power of polarization data and show a few cases where polarization allows us to set spectacular constraints on possible extentions of the LCDM model.

Gamma-rays from type Ia supernova SN2014J
April 24, 2015 | LASR Conference Room | 12:00 PM
Eugene Churazov, Max Planck Institute for Astrophysics

SN2014J is the closest type Ia supernova in the era of space observatories and the first one from which gamma-ray lines have been detected with high significance. The flux of Co-56 lines at 847 and 1238 keV, observed with INTEGRAL, shows that about 0.6 Msun of radioactive Ni-56 has been synthesized during explosion. The line broadening suggests the characteristic expansion velocity of ~10000 km/s. Annihilation of positrons produced during decay of Co-56 makes significant contribution to the continuum below 511 keV. The total mass of the ejecta is consistent with 1.4 Msun progenitor, although the constraints are not very tight. Overall the gamma-ray data are broadly consistent with the expectations for canonical 1D models, such as delayed detonation or deflagration models for a near-Chandrasekhar mass White Dwarf. Pure detonation models or strongly sub-Chandrasekhar models are excluded by the gamma-ray data.

Partially Massless Charges and Monopoles
May 1, 2015 | LASR conference room | 12:00 PM
Rachel A Rosen, Columbia University

In this talk I'll discuss an exotic theory of gravity known as "partially massless" gravity. The linear partially massless theory displays many features analogous to those of electromagnetism, including an electric/magnetic duality. However, the structure of gauge charges is much richer than in E&M. I'll present the analogues of electric point charges and Dirac monopoles and discuss possible applications.

Probing New Physics Beyond the Standard Model with Cosmology
May 8, 2015 | LASR Conference Room | 12:00 PM
Cora Dvorkin, Harvard University

Cosmological observations have provided us with answers to age-old questions, involving the age, geometry, and composition of the universe. However, there are profound questions that still remain unanswered. In this talk, I will describe ongoing efforts to shed light on some of these questions. The origin of the small anisotropies that later grew into the stars and galaxies that we see today is still unknown. In the first part of this talk, I will explain how we can use measurements of the CMB and the large-scale structure of the universe to reconstruct the detailed physics of very early epochs, when the universe was only a tiny fraction of a second old. In the last part of the talk, I will discuss how we can use observations of the CMB and the large-scale structure of the universe to improve our understanding of another open question in fundamental physics. Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time. I will identify cosmological processes in which the particle interactions of dark matter are of relevance and show how we can use current and future cosmological data to probe these interactions both at large and small scales.

Re-Examining Astrophysical Constraints on the Dark Matter Model
May 15, 2015 | LASR conference room | 12:00 PM
Alyson Brooks, Rutgers University

The cosmological model based on cold dark matter (CDM) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our Universe. However, at small scales (in the smallest galaxies and at the centers of larger galaxies), a number of observations seem to conflict with the predictions CDM cosmology, leading to recent interest in Warm DarkMatter (WDM) and Self-Interacting Dark Matter (SIDM) models. These small scales, though, are also regions dominated by the influence of baryons. I will present results from high resolution cosmological galaxy simulations that include both baryons and dark matter to show that baryonic physics can significantly alter the dark matter structure and substructure of galaxies, revolutionizing our expectations for galaxy structure and influencing our interpretation of the Dark Matter model.

Probing the environments of supermassive black-hole binaries with pulsar timing arrays
May 22, 2015 | LASR conference room | 12:00 PM
Sean McWilliams, West Virginia University

While pulsar timing arrays (PTAs) like NANOGrav have not yet detected gravitational waves, they are still giving us useful information about supermassive black-hole binaries in our Universe. In particular, the continuing non-detection of gravitational waves at current sensitivity levels already suggests that dynamical effects other than gravitational-wave emission are either much more or else much less efficient than we previously thought. I will present detailed calculations of the influence of these other effects on the gravitational-wave signal that we hope to detect with PTAs. I will also present results using the actual 9-year data set from NANOGrav that show how models that include effects other than gravitational-wave emission are already favored over models that only include gravitational-wave emission. Finally, I will present results using realistic simulated PTA data that show what conclusions we will be able to draw regarding the environments and the dynamics of supermassive black-hole binaries at ~milliparsec separations over the next several years.

Cosmic Flows: cosmology and astrophysics from galaxy velocities
May 29, 2015 | LASR conference room | 12:00 PM
Simone Ferraro, Princeton University

Velocity fields are a powerful probe of structure formation and the energy content of our Universe. Additionally, the motion of ionized gas on intermediate scales can be used to measure the clustering of baryons and shed light on galaxy formation and feedback mechanisms. I will discuss techniques that can be used to both constrain cosmology and measure baryon properties. I will also present some preliminary results.