Colloquia & Seminars, 2015
2015
DateColloquia & Seminars
January 7, 2015
3:00 PM
Astronomy colloquium
Neal Dalal, University of Illinois, Urbana-Champaign
Probing structure formation beyond LCDM
January 9, 2015
12:00 PM
Friday noon seminar
Miguel A. Mostafa, Penn State University
First results from the High Altitude Water Cherenkov Observatory
January 14, 2015
3:00 PM
Astronomy colloquium
Adrian Liu, University of California, Berkeley
Frontiers in Cosmology and Radio Astronomy: 21cm cosmology as a probe of reionization and beyond
January 16, 2015
12:00 PM
Friday noon seminar
Sean Tulin, York University
Dark matter halos as particle colliders
January 21, 2015
3:00 PM
Astronomy colloquium
Gwen Rudie, Observatories of the Carnegie Institution for Science
The Circumgalactic and Interstellar Medium of Star-Forming Galaxies at 2<z<3
January 23, 2015
12:00 PM
Friday noon seminar
Andrew B Newman, Carnegie Observatories
Observing the Assembly of Dark Matter and Baryons in Massive Galaxies
January 28, 2015
3:00 PM
Astronomy colloquium
Leslie Rogers, Caltech
Origins and Demographics of Super-Earth and Sub-Neptune Sized Planets
January 30, 2015
12:00 PM
Friday noon seminar
Gordan Krnjaic, Perimeter Institute for Theoretical Physics
Decisively probing sub-GeV vector-portal dark matter with next generation electron-beam experiments
February 4, 2015
3:00 PM
Wednesday colloquium
Carlos Wagner, University of Chicago/Argonne
Baryogenesis and New Physics
February 6, 2015
12:00 PM
Friday noon seminar
Tobias Marriage, Johns Hopkins University
Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''
February 11, 2015
3:00 PM
Astronomy colloquium
Beth Willman, Haverford College
Triumphs and tribulations of near-field cosmology with wide-field surveys: a biased perspective
February 13, 2015
12:00 PM
Friday noon seminar
Colin Bischoff, Harvard-Smithsonian Center for Astrophysics
Joint Analysis of BICEP2, Keck Array, and Planck
February 18, 2015
3:00 PM
Wednesday colloquium
Scott Dodelson, The University of Chicago
Sterile Neutrinos in Particle Physics and Cosmology
February 20, 2015
12:00 PM
Friday noon seminar
Marko Simonovic, IAS, Princeton
Consistency Relations for Large Scale Structure
February 25, 2015
3:00 PM
Astronomy colloquium
Daniel Stark, University of Arizona
Galaxies in the Reionzation Era
February 27, 2015
12:00 PM
Friday noon seminar
Dan Scolnic, University of Chicago
What's Next for Cosmology with Type Ia Supernovae
March 4, 2015
3:00 PM
Wednesday colloquium
Jean-Loup L Puget, Institut d'Astrophysique Spatiale, univeresité Paris Sud
Overview of the 2015 Planck full mission results
March 6, 2015
12:00 PM
Friday noon seminar
Simona Murgia, UC Irvine
Indirect Detection of Dark Matter with Gamma Rays
March 11, 2015
3:00 PM
Astronomy colloquium
Richard Ellis, Caltech
Studies of Star-Forming Galaxies in the Reionization Era
March 18, 2015
3:00 PM
Wednesday colloquium
Daniel J Eisenstein, Harvard University
Baryon Acoustic Oscillations: A Robust and Precise Route to the Cosmological Distance Scale
March 20, 2015
12:00 PM
Friday noon seminar
Michael Zemcov, California Institute of Technology
Near-IR Background Fluctuations Results from the Cosmic Infrared Background Experiment
April 1, 2015
3:00 PM
Astronomy colloquium
Kendrick Smith, Perimeter Institute
Primordial non-Gaussianity in the CMB and Large-Scale Structure
April 3, 2015
12:00 PM
Friday noon seminar
Laura Newburgh, Dunlap Institute, University of Toronto
Measuring Dark Energy with CHIME
April 8, 2015
3:00 PM
Wednesday colloquium
John M Kovac, Harvard University
Measurements of B-mode Polarization at Degree Angular Scales with the BICEP / Keck Experiments
April 15, 2015
3:00 PM
Astronomy colloquium
Daniel Green, University of Toronto
Probing the Nature of Inflation
April 17, 2015
12:00 PM
Friday noon seminar
Silvia Galli, The University of Chicago
Cosmological results from Planck 2015
April 22, 2015
3:00 PM
Wednesday colloquium
Maura McLaughlin, West Virginia University
A Galactic Scale Gravitational Wave Observatory
April 24, 2015
12:00 PM
Friday noon seminar
Eugene Churazov, Max Planck Institute for Astrophysics
Gamma-rays from type Ia supernova SN2014J
April 29, 2015
3:00 PM
Astronomy colloquium
Andrew MacFadyen, New York University
Binary Black Hole Accretion
May 1, 2015
12:00 PM
Friday noon seminar
Rachel A Rosen, Columbia University
Partially Massless Charges and Monopoles
May 6, 2015
3:00 PM
Wednesday colloquium
Keith Bechtol, WIPAC / University of Wisconsin-Madison
News on the search for Milky Way satellite galaxies
May 8, 2015
12:00 PM
Friday noon seminar
Cora Dvorkin, Harvard University
Probing New Physics Beyond the Standard Model with Cosmology
May 13, 2015
3:00 PM
Astronomy colloquium
Piero Madau, University of California Observatories
The Dark and Light Side of Galaxy Formation
May 15, 2015
12:00 PM
Friday noon seminar
Alyson Brooks, Rutgers University
Re-Examining Astrophysical Constraints on the Dark Matter Model
May 20, 2015
3:00 PM
Wednesday colloquium
Lisa Randall, Harvard
Double Disk Dark Matter
May 22, 2015
12:00 PM
Friday noon seminar
Sean McWilliams, West Virginia University
Probing the environments of supermassive black-hole binaries with pulsar timing arrays
May 27, 2015
3:00 PM
Astronomy colloquium
Edo Berger, Harvard University
Short-Duration Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources
May 29, 2015
12:00 PM
Friday noon seminar
Simone Ferraro, Princeton University
Cosmic Flows: cosmology and astrophysics from galaxy velocities
June 10, 2015
3:00 PM
Astronomy colloquium
Josh Winn, MIT
The shortest-period planets
October 2, 2015
12:00 PM
Friday noon seminar
Moritz Munchmeyer, Institute d'Astrophysique Paris
Oscillations in the CMB bispectrum
October 9, 2015
12:00 PM
Friday noon seminar
Ritoban Basu Thakur, The University of Chicago
WIMP-Search Results from the Second CDMSlite Run
October 16, 2015
12:00 PM
Friday noon seminar
Rampei Kimura, New York University
Healthy solutions in the decoupling limit of quasi-dilaton theory
October 23, 2015
12:00 PM
Friday noon seminar
Elisabeth Krause, KIPAC, Stanford
Combining Probes of Large-Scale Structure in the Precision Cosmology Era
October 28, 2015
3:00 PM
Wednesday colloquium
Marc Kamionkowski, Johns Hopkins University
The Future of Cosmological Physics: New Avenues
November 4, 2015
3:00 PM
Wednesday colloquium
Simon White, Max Planck Institute for Astrophysics
The formation and evolution of the galaxy population
November 6, 2015
12:00 PM
Friday noon seminar
Kumiko Kotera, Institut d'Astrophysique de Paris
Observing the transient sky with the highest energy multi-messengers
November 13, 2015
12:00 PM
Friday noon seminar
Lasha Berezhiani, Princeton University
Superfluid Dark Matter
November 20, 2015
12:00 PM
Friday noon seminar
Alexander van Engelen, Canadian Institute for Theroetical Astrophysics
Lensing and Other Results from ACTPol
December 2, 2015
3:00 PM
Wednesday colloquium
Raphael Flauger, The University of Texas at Austin
Planck, BICEP, and the Early Universe
December 4, 2015
12:00 PM
Friday noon seminar
Steve Rodney, University of South Carolina
Stellar Explosions, Strongly Lensed

Probing structure formation beyond LCDM
January 7, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Neal Dalal, University of Illinois, Urbana-Champaign

Cosmological structure formation has long been recognized as a sensitive probe of fundamental physics, especially physics beyond the Standard Model, and recent years have seen tremendous progress in our understanding of structure formation, both from the observational and theoretical sides. In this talk, I will describe some of my group's work on this subject. First, I will discuss a novel method we have developed for numerically simulating nonlinear structure formation in cosmologies where traditional N-body simulations produce large errors. I'll present preliminary results of our simulations for cosmologies with massive neutrinos, and I will describe a new potential signature of neutrino mass in large-scale structure. Finally, I will describe how upcoming ALMA observations of sources from the South Pole Telescope will vastly improve our knowledge of small-scale cosmic structure, thereby constraining the physics of inflation and dark matter.

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


Frontiers in Cosmology and Radio Astronomy: 21cm cosmology as a probe of reionization and beyond
January 14, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Adrian Liu, University of California, Berkeley

In recent years, 21cm cosmology has emerged as an exciting new way to map our Universe. By using the 21cm hyperfine transition as a tracer of neutral hydrogen, one is sensitive not only to the large scale distribution of matter, but also to the astrophysical conditions of the high-redshift intergalactic medium (IGM). The redshifted 21cm line is therefore particularly well-suited for understanding the as-yet unobserved Epoch of Reionization (EoR), a key part of our cosmic history when the first luminous objects were formed and systematically ionized the IGM.

In this talk, I will highlight recent progress in 21cm cosmology, including recent observations from the Precision Array for Probing the Epoch of Reionization (PAPER). These observations disfavor “cold reionization” scenarios, where early luminous sources did little to reheat the IGM. Along the way, I will discuss novel techniques that have been developed for moving beyond technical hurdles (such as foreground contamination) to a first detection of the cosmological 21cm signal. I will conclude by introducing the Hydrogen Epoch of Reionization Array (HERA), a recently commenced experiment that promises to make high signal-to-noise measurements of the power spectrum of 21cm emission. This will not only provide new and direct observational constraints on the EoR, but will also benefit other cosmological probes by reducing uncertainties on a key epoch of cosmic history, thus transforming 21cm cosmology from a promising theoretical idea to a practical way to probe our Universe.

Dark matter halos as particle colliders
January 16, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

The Circumgalactic and Interstellar Medium of Star-Forming Galaxies at 2<z<3
January 21, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Gwen Rudie, Observatories of the Carnegie Institution for Science

The exchange of baryons between galaxies and their surrounding intergalactic medium (IGM) is a crucial but poorly-constrained aspect of galaxy formation and evolution. I will present results from the Keck Baryonic Structure Survey (KBSS), a unique spectroscopic survey designed to explore both the physical properties of high-redshift galaxies and their connection with the surrounding intergalactic baryons. The KBSS is optimized to trace the cosmic peak of star formation (z~2-3), combining high-resolution spectra of 15 hyperluminous QSOs with densely-sampled galaxy redshift surveys surrounding each QSO sightline. I will characterize the physical properties of the gas within the circumgalactic medium (CGM) through measurements of the spatial distribution, column densities, and kinematics of ~6000 HI absorbers surrounding ~900 foreground star-forming galaxies that lie within 50 kpc to 3 Mpc of a QSO sightline. This analysis provides clear evidence of gas inflow and outflow as well as accretion shocks or hot outflows from these forming galaxies. My ongoing study of metallic absorbers in these fields will provide detailed information about the enrichment patterns and overall abundance of metals as a function of distance and velocity, providing a high-fidelity probe of the nature and sphere of influence of galaxy-scale outflows at high-z. I will also discuss KBSS-MOSFIRE, a rest-frame optical spectroscopic survey of more than 800 galaxies in these same QSO fields. These data provide new insight into the physical properties of HII regions at high redshift which show remarkable differences in their ionization and excitation conditions compared to low-redshift star-forming regions. These results have significant implications for both diagnostics of the chemical abundances of high-z galaxies as well as our understanding of massive stars during the peak of cosmic star formation.

Observing the Assembly of Dark Matter and Baryons in Massive Galaxies
January 23, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Origins and Demographics of Super-Earth and Sub-Neptune Sized Planets
January 28, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Leslie Rogers, Caltech

Sub-Neptune, super-Earth-size exoplanets are a new planet class. Though absent from the Solar System, they are found by microlensing, radial velocity, and transit surveys to be common around distant stars. The nature of planets in this regime is not known; terrestrial super-Earths, mini-Neptunes with hydrogen-helium gas layers, and water-worlds with several tens of percent water by mass are all a-priori plausible compositions. Disentangling the contributions from each of these scenarios to the population of observed planets is a critical missing link in our understanding of planet formation, evolution, and interior structure. I will review individual highlights from the diverse complement of sub-Neptune-size planets discovered to date, and present statistical analyses constraining the nature and origins of short-period rocky planets. With the suite of space-based exoplanet transit surveys on the horizon (K2, TESS, CHEOPS and PLATO) and continuing development of ground-based spectrographs (e.g., MAROON-X and G-CLEF), the pace of exoplanet discovery and characterization is poised to continue accelerating. I will conclude by describing pathways forward to identify bulk composition trends in the growing census of known exoplanets and to connect these composition trends back to distinct planet formation pathways.

Decisively probing sub-GeV vector-portal dark matter with next generation electron-beam experiments
January 30, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Baryogenesis and New Physics
February 4, 2015 | 3:00 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Carlos Wagner, University of Chicago/Argonne

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Although physical reality seems to be well described by the Standard Models of Particle Physics and Cosmology, there are many open questions that do not have a direct answer within this framework. An important one is why is there Matter and not Antimatter in the Universe. The conditions for a dynamical generation of the asymmetry between matter and antimatter (baryogenesis) are well known, but cannot be fulfilled within the Standard Models framework. I will explain what are the basic conditions that must be fulfilled for baryogenesis to occur, some general classes of models in which baryogenesis is realized and the possible tests of these models in the near future.

Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''
February 6, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Triumphs and tribulations of near-field cosmology with wide-field surveys: a biased perspective
February 11, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
A map of dwarf galaxies orbiting the Milky Way. Each dwarf contains up to several billion stars, compared to several hundred billion in the Milky Way.

Image credit: J. Bullock, M. Geha, R. Powell
Astronomy colloquium
Beth Willman, Haverford College

Over the last decade, wide-field surveys have revolutionized our view of the Milky Way's stellar halo and dwarf galaxy population. Much of this observational progress has been motivated by a series of apparent "crises" for our cosmological model: the missing satellites problem, too big to fail, and the apparent planar distribution of dwarf satellite galaxies. These challenges have effectively functioned as flashlights pointing us to interesting galaxy formation physics. I will highlight related observational progress in our understanding of galaxy formation using near-field observations. I will then focus on the limiting impacts of observational bias and ways that current and future surveys will be used to tackle these biases. In particular, I will present new predictions for the number of Milky Way dwarf galaxies expected to be discovered in DES and LSST, RR Lyrae stars as a tool to discover dwarf galaxies in previously unexplored territory, and the use of M giant stars to map the Milky Way's halo beyond its virial radius.

Image credit: J. Bullock, M. Geha, R. Powell

Joint Analysis of BICEP2, Keck Array, and Planck
February 13, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Sterile Neutrinos in Particle Physics and Cosmology
February 18, 2015 | 3:00 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Scott Dodelson, The University of Chicago

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The matter particle with the smallest mass, the neutrino, is also the most abundant in the Universe. Since their discovery, neutrinos have continually surprised us. Every time we think we understand the full scope of neutrino physics, data prove us wrong. We now understand the full scope of neutrino physics and can explain almost all observations with a simple 3-flavor model. Will upcoming data from accelerators and the cosmos prove us wrong yet again?

Consistency Relations for Large Scale Structure
February 20, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Galaxies in the Reionzation Era
February 25, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Daniel Stark, University of Arizona

Deep infrared images from the Hubble and Spitzer Space Telescopes have recently pushed the cosmic frontier back to just 500 million years after the Big Bang, delivering the first reliable census of galaxies in what is likely the heart of the reionization era. I will discuss implications of these results for the build-up of stellar mass in early galaxies. I will then present the latest results of a large ground-based spectroscopic program aimed at using the Lyman-alpha emission line as a probe of the ionization state of the IGM at z>7. The results indicate that Lyman-alpha is strongly attenuated in galaxies at z=7-8, as would be expected if the IGM is still partially neutral. Finally, I will introduce a new approach to the spectroscopic study of galaxies at z>7. I will demonstrate that various metal lines in the rest-UV are much stronger in early galaxies than we expected. I will discuss a large new observational campaign aimed at targeting these lines in the brightest known gravitationally-lensed galaxies with the goal of providing the first constraints on the metallicity, ionizing spectrum, and stellar populations of galaxies in the reionization era.

What's Next for Cosmology with Type Ia Supernovae
February 27, 2015 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Dan 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.

Overview of the 2015 Planck full mission results
March 4, 2015 | 3:00 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Jean-Loup L Puget, Institut d'Astrophysique Spatiale, univeresité Paris Sud

The Planck collaboration has released the results from the full mission including polarisation.
The Planck space mission has fulilled its initial goal of extracting essentially all the cosmological information in the temperature map of the Cosmic Microwave Background. It has also detected the polarisation cosmological signals with unprecedented sensitivity over the whole sky.
The Planck mission performances will be illustrated by some spectacular improvements in calibration and reduction of polarized sytematic effects. The Planck view of the polarized microwave sky will be presented.
The extreme stability of the L-CDM cosmological parameters determined either from the temperature or polarization data is leading to a « standard cosmolgy model ». This includes also parameters related to the primordial universe physics.
The polarised foreground emission from interstellar dust has been mapped with a spectacular accuracy. The claim for detection of primordial gravity waves from the BICEP2 team using CMB data aquired from south pole will be discussed in the light of the dust B modes signal observed by Planck and the recent BICEP2-Plkanck paper. The future of the search for primordial B modes will be discussed.

Indirect Detection of Dark Matter with Gamma Rays
March 6, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Studies of Star-Forming Galaxies in the Reionization Era
March 11, 2015 | 3:00 PM | BSLC 001 | Astronomy colloquium
Astronomy colloquium
Richard Ellis, Caltech

Deep exposures with the Hubble Space Telescope (HST) have provided the primary evidence that star-forming galaxies were present in the first billion years of cosmic history. Sometime during this early period the intergalactic medium transitioned from a neutral gas to one that is fully ionized. How did this 'cosmic reionization' occur and were star-forming galaxies responsible? Recent imaging of deep fields with HST's Wide Field Camera 3 in conjunction with Spitzer photometry and Keck spectroscopy has provided important new insight into understanding when reionization occurred and the role of early galaxies in the process. Gravitational lensing by foreground clusters is providing complementary evidence. I will review this rapid progress in our understanding of what could be considered the last missing piece in our overall picture of cosmic history and discuss the remaining challenges ahead of future facilities such as TMT, GMT and JWST.

Baryon Acoustic Oscillations: A Robust and Precise Route to the Cosmological Distance Scale
March 18, 2015 | 3:00 PM | BSLC 001 | Wednesday colloquium
Wednesday colloquium
Daniel J Eisenstein, Harvard University

I will discuss how the acoustic oscillations that propagate in the photon-baryon fluid during the first million years of the Universe provide a robust method for measuring the cosmological distance scale. The distance that the sound can travel can be computed to high precision and creates a signature in the late-time clustering of matter that serves as a standard ruler. Galaxy clustering results from the Sloan Digital Sky Survey reveal this feature, giving geometric distances to a wide range of redshifts and producing an accurate measurement of the abundance of dark energy. I will review our recent work on the theory and practice of the acoustic oscillation method and our latest cosmology results from SDSS-III on the expansion history of the Universe.

Near-IR Background Fluctuations Results from the Cosmic Infrared Background Experiment
March 20, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Primordial non-Gaussianity in the CMB and Large-Scale Structure
April 1, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Kendrick Smith, Perimeter Institute

I'll give a pedagogical review of inflation and explain how its physics can be constrained by searching for "primordial non-Gaussianity", i.e. differences between the statistics of the initial curvature field in our universe and the statistics of an ideal Gaussian field. Then I'll talk about observational CMB constraints, including some new results from Planck. Finally I'll discuss future prospects for improving Planck constraints with large-scale surveys such as Euclid and LSST.

Measuring Dark Energy with CHIME
April 3, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Measurements of B-mode Polarization at Degree Angular Scales with the BICEP / Keck Experiments
April 8, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
Wednesday colloquium
John M Kovac, Harvard University

The theory of cosmic inflation postulates that the initial conditions of our observable universe arose from quantum fluctuations during a very early burst of exponential expansion. The BICEP / Keck Array experiments are a series of cosmic microwave background (CMB) polarimeters specifically designed to search for gravitational waves predicted by inflation by looking for the faint B-mode patterns they would imprint on degree-scale CMB polarization. Observing from the South Pole between 2010 and 2012, the BICEP2 telescope made maps of unprecedented sensitivity at degree angular scales over 2% of the sky, In March 2014 the BICEP2 team reported a high signal-to-noise detection of B-mode polarization at 150 GHz, at a level well above typical predictions of galactic foreground models for that region of sky, and consistent with a large contribution from inflationary gravitational waves. However, later last year high-frequency results reported by the Planck satellite indicated levels of polarized emission from galactic dust potentially high enough to account for the entire BICEP2 signal. In a recently published joint analysis that combines data from BICEP2, the Keck Array, and the Planck satellite, we find that there is not currently significant evidence for a gravitational wave signal, and we set the tightest constraints yet on its possible level. I will describe our current results and the continuing hunt for inflationary gravitational waves with the BICEP / Keck Array experimental program.

Probing the Nature of Inflation
April 15, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Daniel Green, University of Toronto

The idea that the early universe included an era of accelerated expansion (Inflation) was proposed to explain very qualitative features of the first cosmological observations. Since then, our observations have improved dramatically and have lead to high precision agreement with the predictions of the first models of inflation, slow-roll inflation. At the same time, there has been significant growth in the number of mechanisms for inflation, many of which are qualitatively distinct from slow-roll.
Nevertheless, most of these ideas are also consistent with current data. In this talk, I will first review inflation and its current observational status. I will then discuss the important theoretical targets for the future and the prospects for achieving them.

Cosmological results from Planck 2015
April 17, 2015 | 12:00 PM | LASR Conference Room | Friday noon seminar
Friday noon seminar
Silvia Galli, The 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.

A Galactic Scale Gravitational Wave Observatory
April 22, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
Wednesday colloquium
Maura McLaughlin, West Virginia University

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Pulsars are rapidly rotating neutron stars with phenomenal rotational stability that can be used as celestial clocks in a variety of fundamental physics experiments. One of these experiments involves using an array of precisely timed millisecond pulsars to detect perturbations due to gravitational waves. The gravitational waves detectable through pulsar timing will most likely result from an ensemble of supermassive black hole binaries. I will describe the efforts of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), a collaboration which monitors an array of over 40 millisecond pulsars with the Green Bank Telescope and Arecibo Observatory. The most recent limits on various types of gravitational wave sources will be presented, and I will show how these limits are already constraining models for galaxy formation and evolution and the tension of cosmic strings. I will then describe the dramatic gains in sensitivity that are expected from discoveries of millisecond pulsars, more sensitive instrumentation, improved detection algorithms, and international collaboration and show that detection is possible before the end of the decade.

Gamma-rays from type Ia supernova SN2014J
April 24, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Binary Black Hole Accretion
April 29, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Andrew MacFadyen, New York University

Binary black hole mergers in the presence of gaseous accretion flows are prime candidates for simultaneous observations of both gravitational waves and electromagnetic signals. I will present the results of 2D hydrodynamical simulations of circumbinary disk accretion using the moving-mesh code DISCO. These simulations demonstrate that gas accretion is not impeded by binarity. Gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent "mini-disks" surrounding each black hole. I will discuss characteristic periodicity in the measured accretion rate onto each BH, with implications for the quasar PG 1302-102 which shows evidence for periodic variability, as well as the dependence of the accretion flow on the binary mass ratio. I will also discuss characteristic modifications to the spectrum which arise from shock heated gas inside the circumbinary cavity. Finally, I will discuss simulations which include binary inspiral and merger due to gravitational wave emission in order to track the changes in accretion and electromagnetic radiation as the orbit shrinks.

Partially Massless Charges and Monopoles
May 1, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

News on the search for Milky Way satellite galaxies
May 6, 2015 | 3:00 PM | BSLC 115 | Wednesday colloquium
Wednesday colloquium
Keith Bechtol, WIPAC / University of Wisconsin-Madison

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The population of Milky Way satellite galaxies includes the least luminous, least chemically evolved, and most dark matter dominated galaxies in the known universe. These extreme objects have reshaped how we define a "galaxy" and provide a unique testing ground for both galaxy formation models and the cold dark matter paradigm. The current census of satellite galaxies surrounding the Milky Way is almost certainly incomplete. Ongoing and near-future wide-field optical imaging surveys are anticipated to find hundreds of ultra-faint Milky Way companions at lower luminosities, greater distances, and in less explored regions of the sky. A dozen new stellar systems have already been reported in 2015, and at least one these, Reticulum II, has now been dynamically and chemically confirmed as a galaxy. I will place these recent results in context and discuss how the emergent population of Milky Way satellites might enhance the sensitivity of indirect dark matter searches.

Probing New Physics Beyond the Standard Model with Cosmology
May 8, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

The Dark and Light Side of Galaxy Formation
May 13, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Piero Madau, University of California Observatories

In recent years, precision measurements across cosmic time have led to a widely accepted cosmological paradigm for galaxy assembly and evolution, the cold dark matter (ΛCDM) model. Within this theory, galaxies form "bottom-up," with low-mass objects ("halos") collapsing earlier and merging to form larger and larger systems over time. Ordinary matter follows the dynamics dictated by the dominant dark matter until radiative, hydrodynamic, and star-formation processes take over. Although ΛCDM has had great success in explaining the observed large-scale distribution of mass in the universe, the nature of the dark matter particle is best tested on small scales, where its physical characteristics manifest themselves by modifying the structure of galaxy halos and their lumpiness. It is on these scale that detailed comparisons between observations and theory have revealed several discrepancies and challenged our understanding of the mapping between dark matter halos and their baryonic components. In this talk I will review some of the triumphs and tribulations of the theory. While the latter may indicate the need for more complex physics in the dark sector itself, emerging evidence suggests that a poor understanding of the baryonic processes involved in galaxy formation may be at the origin of these controversies.

Re-Examining Astrophysical Constraints on the Dark Matter Model
May 15, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Double Disk Dark Matter
May 20, 2015 | 3:00 PM | BSLC 109 | Wednesday colloquium
Lisa Randall
Frank B. Baird, Jr., Professor of Science, Harvard University
Photo credit: Tsar Fodorsky.
Wednesday colloquium
Lisa Randall, Harvard

I will describe Partially Interacting Dark Matter and a possible consequence, Double Disk Dark Matter in which a dark matter disk is embedded in the baryonic disk. I will discuss possible implications and observational consequences and constraints, including implications for the satellites of the Andromeda Galaxy.

Probing the environments of supermassive black-hole binaries with pulsar timing arrays
May 22, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

Short-Duration Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources
May 27, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Edo Berger, Harvard University

Gamma-ray bursts are the most luminous and energetic explosions known in the universe. They appear in two varieties: long- and short-duration. The long GRBs result from the core-collapse of massive stars, but until recently the origin of the short GRBs was shrouded in mystery. In this talk I will present several lines of evidence that point to the merger of compact objects binaries (NS-NS and/or NS-BH) as the progenitor systems of short GRBs. Within this framework, the observational data allow us to determine the merger rate of these systems as input to Advanced LIGO, to infer the electromagnetic properties of gravitational wave sources, and to study r-process nucleosynthesis.

Cosmic Flows: cosmology and astrophysics from galaxy velocities
May 29, 2015 | 12:00 PM | LASR conference room | Friday noon seminar
Friday noon seminar
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.

The shortest-period planets
June 10, 2015 | 3:00 PM | BSLC 115 | Astronomy colloquium
Astronomy colloquium
Josh Winn, MIT

Short-period planets were a gift from nature that enabled the rapid acceleration of exoplanetary science. They are more readily studied than long-period planets, and their existence and orbital properties pose interesting questions. I will present the results of a search for the shortest-period transiting planets, using data from the Kepler spacecraft. The results show that 0.5% of Sun-like stars have orbiting "lava worlds": terrestrial planets with periods ranging from 4 hours to one day. The search also revealed a new class of objects that seem to be small rocky planets disintegrating in the blazing heat from their parent stars. Finally, I will describe an upcoming NASA mission, the Transiting Exoplanet Survey Satellite (TESS), which will identify thousands of short-period planets around the nearest and brightest stars in the sky.

Oscillations in the CMB bispectrum
October 2, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Planck data is used to search for bispectrum oscillations.
Friday noon seminar
Moritz Munchmeyer, Institute d'Astrophysique Paris

Oscillating signatures in the correlation functions of the primordial density perturbations are predicted by a variety of inflationary models. A theoretical mechanism that has attracted much attention is a periodic shift symmetry as implemented in axion monodromy inflation. This symmetry leads to resonance non-gaussianities, whose key feature are logarithmically stretched oscillations. Oscillations are also a generic consequence of excited states during inflation and of sharp features in the potential. Oscillating shapes are therefore a very interesting experimental target.
After giving an overview of these motivations, I will discuss how to search for these signatures in the CMB. Fast oscillations are difficult to search for with traditional estimation techniques, and I will demonstrate how targeted expansions, that exploit the symmetry properties of the shapes, allow to circumvent these difficulties. As a member of the Planck collaboration, I will discuss the Planck results that have been obtained using these methods in the bispectrum, as well as a joint search using bispectrum and power spectrum. Due to their low overlap with other non-gaussian shapes, oscillating bispectrum shapes are not exhaustively constrained and a potential discovery is therefore not yet ruled out.
My talk will be based in particular on arxiv:1412.3461, arxiv:1505.05882 and Planck publications on inflation and non-gaussianities.

WIMP-Search Results from the Second CDMSlite Run
October 9, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Ritoban Basu Thakur, The University of Chicago

The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg days, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded for WIMP masses between 1.6 and 5.5 GeV/c^2.

Healthy solutions in the decoupling limit of quasi-dilaton theory
October 16, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Rampei Kimura, New York University

Quasidilaton massive gravity is an extension of massive General Relativity to a theory with additional scale invariance and approximate internal Galilean symmetry. In this talk, I will present a detailed study of the spherically symmetric solutions which are free of ghosts, tachyons, gradient instability, and superluminality for all propagating modes in a theory of quasidilaton.

Combining Probes of Large-Scale Structure in the Precision Cosmology Era
October 23, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Elisabeth Krause, KIPAC, Stanford

Current and upcoming wide-field large-scale structure surveys, such as DES and LSST, will enable precision measurements of various observables of large-scale structure, such as weak lensing, galaxy clustering, and the abundance of galaxy clusters. These observables probe different aspects of cosmic structure formation, and combining them improves constraints on cosmology significantly. However, these observables probe the same underlying density field, and the information content is correlated. Additionally, they share correlated (astrophysical and observational) systematic effects.
In this talk I will introduce the analysis concepts for the joint analysis of probes of large-scale structure currently under development for CosmoLike, a fast and self-consistent LSS likelihood analysis package. Using a simulated DES combined probes analysis as an example, I will discuss cross-correlations of observables, and modeling and mitigation of systematic uncertainties affecting multiple probes, and in particular give a quantitative comparison of different weak lensing systematics.

The Future of Cosmological Physics: New Avenues
October 28, 2015 | 3:00 PM | ERC 401 | Wednesday colloquium
Wednesday colloquium
Marc Kamionkowski, Johns Hopkins University

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We now have a highly successful cosmological model in place, but one which leaves many questions unanswered. What is the new physics responsible for primordial perturbations? What is the dark matter? What causes an accelerated cosmic expansion? And why is there a preponderance of matter over antimatter? New generations of galaxy surveys will continue to map the cosmic mass distribution on ever larger scales and with increased precision, while CMB experiments are beginning to map the polarization B modes from inflation and from lensing. It is never too soon, though, to think about what else can be done with these new experiments and in subsequent generations of experiments. In this talk I will discuss a variety of new early-Universe fossils that can be sought with galaxy surveys and discuss new ideas to probe primordial power on scales far smaller than those accessible with galaxy surveys.

The formation and evolution of the galaxy population
November 4, 2015 | 3:00 PM | ERC 161 | Wednesday colloquium
Wednesday colloquium
Simon White, Max Planck Institute for Astrophysics

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Recent observations of the high-redshift universe have characterized the initial conditions for nonlinear structure formation over the full range of scales responsible for dwarf and giant galaxies, galaxy clusters and the large-scale cosmic web. At the same time, wide-field spectroscopic and photometric surveys have measured the abundance and clustering of low-redshift galaxies as a function of mass, size, morphology, kinematic structure, gas content, metallicity, star formation rate and nuclear activity, while deep surveys have explored the evolution of several of these distributions to z>3. Galaxy population simulations aim to interpret these observations within the LCDM structure formation paradigm, thereby constraining the complex, diverse and heavily interconnected astrophysics of galaxy formation.
Recent simulations are broadly consistent with the galaxy abundances and clustering seen in both wide-field and deep surveys, and provide predictions for topics as different as galaxy-galaxy lensing, the triggering and duty cycles of AGN, and the evolution of Tully-Fisher, mass-size and mass-metallicity relations. They show galaxy assembly histories to be strongly constrained by the structure formation paradigm, giving insight into issues such as internally versus externally driven evolution, inflow versus winds, major versus minor mergers, in situ versus ex situ star formation, and disks versus bulges. In addition, simulations can now be adapted to represent any chosen LCDM-like cosmology, allowing a first assessment of whether galaxy formation uncertainties will limit our ability to do precision cosmology with galaxy surveys.

Observing the transient sky with the highest energy multi-messengers
November 6, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Kumiko Kotera, Institut d'Astrophysique de Paris

Kumiko Kotera
In the transient sky are found the most violent phenomena in the universe. The energy production and release of these events is mysterious. Very high energy messengers (photons, neutrinos and cosmic rays at energies >10^14 eV) offer a unique perspective to their study. Transients are indeed the best known sources capable of supplying enough energy and flux to astroparticles at the observed level. In this talk, we will focus on some of these powerful objects (young pulsars, millisecond pulsar systems, superluminous supernovae) and explore their capability to produce the highest energy particles, by building comprehensive scenarios of acceleration, escape and propagation. We will estimate the expected signatures of these scenarios, and compare them to the latest multi-wavelength and multi-messenger data, in order to constrain the source properties. In particular, the expected neutrino signatures will be a good target to be probed by the Giant Radio Array for Neutrino Detection (GRAND) project, that aims at detecting high-energy neutrinos with a 100'000 km2 radio antenna array in the Tianshan mountains in China.

Superfluid Dark Matter
November 13, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Lasha Berezhiani, Princeton University

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I will talk about a novel theory of dark matter superfluidity that matches the success of LCDM model on cosmological scales while simultaneously reproducing the MOND phenomenology on galactic scales.

Image credit: NASA/CXC/SAO

Lensing and Other Results from ACTPol
November 20, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Alexander van Engelen, Canadian Institute for Theroetical Astrophysics

Surveys of the CMB from ground-based observatories have revealed much about cosmology, in particular by measuring effects on CMB photons since recombination. In this talk, I will summarize results from the ongoing ACTPol survey, highlighting in particular the measurement of gravitational lensing by matter between us and the CMB recombination surface. I will discuss challenges with these measurements and also look forward to what will be possible with upcoming surveys such as SPT-3G, AdvACT, and CMB-S4.

Planck, BICEP, and the Early Universe
December 2, 2015 | 3:00 PM | ERC 161 | Wednesday colloquium
Wednesday colloquium
Raphael Flauger, The University of Texas at Austin

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The cosmic microwave background contains a wealth of information about cosmology as well as high energy physics. It tells us about the composition and geometry of the universe, the properties of neutrinos, dark matter, and even the conditions in our universe long before the cosmic microwave background was emitted. After a brief introduction, I will discuss various aspects of the recently released Planck full mission data before turning to a discussion of string inspired models and the search for their signatures. Finally, I will turn to the search for primordial B-modes.

Stellar Explosions, Strongly Lensed
December 4, 2015 | 12:00 PM | ERC 401 | Friday noon seminar
Friday noon seminar
Steve Rodney, University of South Carolina

The Hubble Space Telescope Frontier Fields survey has been extending the reach of HST by targeting massive galaxy clusters that act as cosmic telescopes: using gravitational lensing to amplify the light of distant objects. This makes it possible to detect the explosions of stars that formed when the universe was less than a few billion years old. It also yields a small but special sample: highly magnified supernovae that serve as sensitive probes of the lensing cluster's dark matter potential. I will describe some of the recent discoveries from this program, including a highly magnified Type Ia supernova, a peculiar fast transient observed twice in a multiply-imaged galaxy, and an ancient supernova being multiply imaged by both a galaxy and a galaxy cluster. I will also look ahead to discuss how HST, JWST and WFIRST can help develop strongly-lensed supernovae into a powerful new tool for studying dark matter and dark energy in the next decade.