KICP Seminars & Colloquia, Winter 2015

Seminar schedule for Winter 2015
January 7, 2015
Astronomy Colloquium
Neal Dalal
University of Illinois, Urbana-Champaign
Probing structure formation beyond LCDM   [Abstract]
January 9, 2015
Friday noon seminar
Miguel A. Mostafa
Penn State University
First results from the High Altitude Water Cherenkov Observatory
January 13, 2015
Astronomy Special Seminar
Emily Levesque
University of Colorado
Engines, Lighthouses, and Laboratories: Massive Stars Across the Cosmos   [Abstract]
January 14, 2015
Astronomy Colloquium
Adrian Liu
University of California, Berkeley
Frontiers in Cosmology and Radio Astronomy: 21cm cosmology as a probe of reionization and beyond   [Abstract]
January 16, 2015
Friday noon seminar
Sean Tulin
York University
Dark matter halos as particle colliders   [Abstract]
January 21, 2015
Astronomy Colloquium
Gwen Rudie
Observatories of the Carnegie Institution for Science
The Circumgalactic and Interstellar Medium of Star-Forming Galaxies at 2<z<3   [Abstract]
January 23, 2015
Friday noon seminar
Andrew B Newman
Carnegie Observatories
Observing the Assembly of Dark Matter and Baryons in Massive Galaxies   [Abstract]
January 27, 2015
Astronomy Special Seminar
George Becker
Space Telescope Science Institute
The End of Reionization: An IGM Perspective   [Abstract]
January 28, 2015
Astronomy Colloquium
Leslie Rogers
Caltech
Origins and Demographics of Super-Earth and Sub-Neptune Sized Planets   [Abstract]
January 30, 2015
Friday noon seminar
Gordan Krnjaic
Perimeter Institute for Theoretical Physics
Decisively probing sub-GeV vector-portal dark matter with next generation electron-beam experiments   [Abstract]
February 3, 2015
Astronomy Special Seminar
Ryan Foley
University of Illinois, Urbana-Champaign
Transient Astronomy: Dark Energy, Supernova Physics & Exotica   [Abstract]
February 4, 2015
Wednesday colloquium
Carlos Wagner
University of Chicago/Argonne
Baryogenesis and New Physics   [Abstract | PDF]
February 6, 2015
Friday noon seminar
Tobias Marriage
Johns Hopkins University
Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''   [Abstract]
February 10, 2015
Open Group seminar
Seth R Siegel
California Institute of Technology
Multiwavelength Analysis of Galaxy Clusters   [Abstract]
February 11, 2015
Open Group seminar
Lorenzo Moncelsi
California Institute of Technology
Cosmology above the clouds with SPIDER   [Abstract]
February 11, 2015
Astronomy Colloquium
Beth Willman
Haverford College
Triumphs and tribulations of near-field cosmology with wide-field surveys: a biased perspective   [Abstract]
February 13, 2015
Friday noon seminar
Colin Bischoff
Harvard-Smithsonian Center for Astrophysics
Joint Analysis of BICEP2, Keck Array, and Planck   [Abstract]
February 17, 2015
Open Group seminar
Francis-Yan Cyr-Racine
Caltech/JPL
Talk for ''Dark Matter Hub'' : Graviational Detection of Self-Interacting Dark Matter.
February 18, 2015
Wednesday colloquium
Scott Dodelson
The University of Chicago
Sterile Neutrinos in Particle Physics and Cosmology   [Abstract | PDF]
February 20, 2015
Friday noon seminar
Marko Simonovic
IAS, Princeton
Consistency Relations for Large Scale Structure   [Abstract]
February 20, 2015
Open Group seminar
Matthew Dolan
SLAC National Accelerator Laboratory
A taste of dark matter: Flavour constraints on pseudoscalar mediators.   [Abstract]
February 25, 2015
Astronomy Colloquium
Daniel Stark
University of Arizona
Galaxies in the Reionzation Era   [Abstract]
February 26, 2015
Open Group seminar
Donglian Xu
University of Alabama
Search for Astrophysical Tau Neutrinos in Three Years of IceCube Data   [Abstract]
February 27, 2015
Friday noon seminar
Dan Scolnic
University of Chicago
What's Next for Cosmology with Type Ia Supernovae   [Abstract]
March 4, 2015
Wednesday colloquium
Jean-Loup L Puget
Institut d'Astrophysique Spatiale, univeresité Paris Sud
Overview of the 2015 Planck full mission results   [Abstract]
March 5, 2015
Open Group seminar
Karen Kolb Flude
Aging with Ease, Forward Chicago
Astrophysics for Older Adults   [Abstract]
March 6, 2015
Friday noon seminar
Simona Murgia
UC Irvine
Indirect Detection of Dark Matter with Gamma Rays   [Abstract]
March 11, 2015
Astronomy Colloquium
Richard Ellis
Caltech
Studies of Star-Forming Galaxies in the Reionization Era   [Abstract]
March 18, 2015
Wednesday colloquium
Daniel J Eisenstein
Harvard University
Baryon Acoustic Oscillations: A Robust and Precise Route to the Cosmological Distance Scale   [Abstract]
March 20, 2015
Friday noon seminar
Michael Zemcov
California Institute of Technology
Near-IR Background Fluctuations Results from the Cosmic Infrared Background Experiment   [Abstract]
 
WEDNESDAY COLLOQUIA

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

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

    PDF
    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?
  • March 4, 2015 | 3:00 PM | BSLC 001
    Overview of the 2015 Planck full mission results
    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.
  • March 18, 2015 | 3:00 PM | BSLC 001
    Baryon Acoustic Oscillations: A Robust and Precise Route to the Cosmological Distance Scale
    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.

 
FRIDAY NOON SEMINARS

  • January 9, 2015 | 12:00 PM | LASR conference room
    First results from the High Altitude Water Cherenkov Observatory
    Miguel A. Mostafa, Penn State University
  • January 16, 2015 | 12:00 PM | LASR conference room
    Dark matter halos as particle colliders
    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.
  • January 23, 2015 | 12:00 PM | LASR conference room
    Observing the Assembly of Dark Matter and Baryons in Massive Galaxies
    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.
  • January 30, 2015 | 12:00 PM | LASR conference room
    Decisively probing sub-GeV vector-portal dark matter with next generation electron-beam experiments
    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.
  • February 6, 2015 | 12:00 PM | LASR conference room
    Double Feature: ''SZ and AGN'' and ''The Cosmology Large Angular Scale Surveyor''
    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.
  • February 13, 2015 | 12:00 PM | LASR conference room
    Joint Analysis of BICEP2, Keck Array, and Planck
    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.
  • February 20, 2015 | 12:00 PM | LASR conference room
    Consistency Relations for Large Scale Structure
    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.
  • February 27, 2015 | 12:00 PM | LASR Conference Room
    What's Next for Cosmology with Type Ia Supernovae
    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.
  • March 6, 2015 | 12:00 PM | LASR conference room
    Indirect Detection of Dark Matter with Gamma Rays
    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.
  • March 20, 2015 | 12:00 PM | LASR conference room
    Near-IR Background Fluctuations Results from the Cosmic Infrared Background Experiment
    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.

 
OPEN GROUP SEMINARS

  • February 10, 2015 | 4:00 PM | LASR Conference Room
    Multiwavelength Analysis of Galaxy Clusters
    Seth R Siegel, California Institute of Technology

    I will report on the joint analysis of X-ray, weak lensing, strong lensing, and Sunyaev-Zel'dovich (SZ) measurements of the CLASH sample of 25 massive galaxy clusters. The high-quality multiwavelength data is able to constrain more realistic parametric models for the distribution of dark and baryonic matter in the galaxy clusters, avoiding biases in mass estimates that result from the assumptions of spherical symmetry and hydrostatic equilibrium. I will present results for a subsample of the clusters, including constraints on the level of non-thermal pressure support in the intracluster medium (ICM). I will conclude by introducing the Multiwavelength Sub/millimeter Inductance Camera (MUSIC), a new photometric imaging camera for the Caltech Submillimeter Observatory that is simultaneously sensitive to four bands at 150, 230, 290, and 350 GHz, and is ideally suited for studies of the ICM through the SZ effect. I will describe the characterization and removal of noise sourced by MUSIC's Microwave Kinetic Inductance Detectors (MKIDs) and their readout electronics.
  • February 11, 2015 | 12:00 PM | LASR Conference Room
    Cosmology above the clouds with SPIDER
    Lorenzo Moncelsi, California Institute of Technology

    SPIDER is a balloon-borne microwave polarimeter designed to measure cosmological B-modes on degree angular scales in the presence of Galactic foregrounds. With six independent telescopes housing a total of ~2000 detectors in the 90 GHz and 150 GHz frequency bands, SPIDER is the most instantaneously-sensitive CMB polarimeter deployed on the sky to date. SPIDER was successfully launched from McMurdo Station, Antarctica in January 2015 and acquired science data for 16 days. I will briefly cover the in-flight performance and the expected analysis challenges. Pending recovery, the SPIDER team is already planning the next flight, featuring one or two foreground-optimized channels, which will allow us constrain the primordial tensor-mode amplitude at the level of r < 0.03 (99% CL), even in the presence of foregrounds.
  • February 17, 2015 | |
    Talk for ''Dark Matter Hub'' : Graviational Detection of Self-Interacting Dark Matter.
    Francis-Yan Cyr-Racine, Caltech/JPL
  • February 20, 2015 | 1:30 PM | LASR Conference Room
    A taste of dark matter: Flavour constraints on pseudoscalar mediators.
    Matthew Dolan, SLAC National Accelerator Laboratory

    Dark matter interacting with the Standard Model via a light mediator can induce observable signals in indirect detection experiments and experience large self-interactions, while evading otherwise strong constraints from direct detection experiments. However, new light particles can induce new flavour-changing interactions in the Standard Model, opening alternative avenues to testing these models. In this talk I will present these constraints with a focus on light pseudoscalars. I will discuss the implications for explanations of the DAMA annual modulation and Galactic Centre excess signals.
  • February 26, 2015 | 10:00 AM | LASR Conference Room
    Search for Astrophysical Tau Neutrinos in Three Years of IceCube Data
    Donglian Xu, University of Alabama

    High-energy cosmic neutrinos are expected to be produced in extremely energetic astrophysical sources such as active galactic nuclei (AGNs) and gamma ray bursts (GRBs). The IceCube neutrino observatory has recently detected a diffuse astrophysical neutrino flux at 5.7$sigma $. One of the outstanding questions regarding astrophysical neutrinos is their flavor composition. Most standard oscillation scenarios predict tau neutrinos in the astrophysical flux, which have a negligible background from cosmic ray induced atmospheric neutrinos. I will present the analysis method and results from a recent search for astrophysical tau neutrinos with three years of IceCube data.
  • March 5, 2015 | 10:00 AM | LASR Conference Room
    Astrophysics for Older Adults
    Karen Kolb Flude, Aging with Ease, Forward Chicago

    The KICP has a substantial astronomy/physics/cosmology outreach effort underway at Chicago City Senior Centers, in which we've brought astronomy and physics content to ~200 seniors free of charge, followed by subsidized field trips to the Adler Planetarium. If you think you might be interested in participating, this is the perfect opportunity to get involved. The session will be led by gerontologist Karen Kolb Flude, gerontologist, and KICP postdoc Daniel Grin, on Thursday March 5th, 10 AM-12 PM, in the LASR Building, in the central conference room. The session will begin with a short overview of our existing program. We'll then hear from Karen Flude about the motivation for lifelong learning and senior outreach, the specific challenges seniors face worldwide, and then some important tools for participating in senior outreach effectively. The session will wrap up with an opportunity for attendees to show the group any existing presentation material and then get helpful feedback on tailoring it to a senior citizen audience.

 
ASTRONOMY COLLOQUIA

  • January 7, 2015 | 3:00 PM | BSLC 001
    Probing structure formation beyond LCDM
    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.
  • January 14, 2015 | 3:00 PM | BSLC 001
    Frontiers in Cosmology and Radio Astronomy: 21cm cosmology as a probe of reionization and beyond
    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.
  • January 21, 2015 | 3:00 PM | BSLC 001
    The Circumgalactic and Interstellar Medium of Star-Forming Galaxies at 2<z<3
    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.
  • January 28, 2015 | 3:00 PM | BSLC 001
    Origins and Demographics of Super-Earth and Sub-Neptune Sized Planets
    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.
  • February 11, 2015 | 3:00 PM | BSLC 001
    Triumphs and tribulations of near-field cosmology with wide-field surveys: a biased perspective
    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
  • February 25, 2015 | 3:00 PM | BSLC 001
    Galaxies in the Reionzation Era
    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.
  • March 11, 2015 | 3:00 PM | BSLC 001
    Studies of Star-Forming Galaxies in the Reionization Era
    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.

 
ASTRONOMY SPECIAL SEMINARS

  • January 13, 2015 | 12:00 PM | LASR Conference Room
    Engines, Lighthouses, and Laboratories: Massive Stars Across the Cosmos
    Emily Levesque, University of Colorado

    Massive stars are crucial building blocks in the study of star-forming galaxies, stellar evolution, and transient events, and their applications as astrophysical tools span a broad range of subfields. The radiative signatures of young star-forming galaxies are powered by their massive stellar populations. Transient phenomena act as observational beacons, ranging from local non-terminal events signaling the death throes of extreme massive stars to long-duration gamma-ray bursts that can serve as powerful probes of the high-redshift universe. Finally, resolved massive star populations offer a treasure trove of nearby targets, allowing us to closely examine their physical parameters, evolution, and contribution to chemical enrichment. I will present my current research programs focused on developing a comprehensive picture of massive stars across the cosmos: observational surveys and models of star-forming galaxies, progenitor and host environment studies of transient phenomena, and extragalactic stellar observations, including the recent discovery of the first Thorne-Zytkow object candidate. Combined, this work will make substantial progress in our understanding of massive stars over the coming decade. This in turn will equip us with the tools we need to take full advantage of the frontiers opened up by new observational facilities such as the GMT, LSST, and JWST, allowing us to immediately begin probing the new corners of the universe that they reveal.
  • January 27, 2015 | 12:00 PM | LASR Conference Room
    The End of Reionization: An IGM Perspective
    George Becker, Space Telescope Science Institute

    The epoch of reionization was a period of intense interaction between luminous objects and their surroundings. Consequently, along with tracking the cosmic history of baryons, determining when and how the intergalactic medium (IGM) was reionized provides fundamental insights into the first stars and galaxies. I will describe a set of recent projects that examine reionization by using quasar absorption lines to probe the IGM at the highest observable redshifts. The results help to clarify when reionization ended and the role played by galaxies, but also pose significant challenges to current reionization models. I will describe the next steps forward, and some of the potential avenues for IGM science with next-generation observing facilities.
  • February 3, 2015 | 12:00 PM | LASR Conference Room
    Transient Astronomy: Dark Energy, Supernova Physics & Exotica
    Ryan Foley, University of Illinois, Urbana-Champaign

    We are currently in a golden age of transient astronomy. Repeated imaging of large areas of the sky have revealed celestial objects that change on a human timescale. LSST and WFIRST, the top ground-based and space-based priorities for the entire astronomical community, are inherently transient surveys. Because of these upcoming facilities combined with follow-up capabilities from upcoming facilities such as GMT, this field will continue to grow for the foreseeable future. Scientifically, transient astronomy holds significant potential for major discoveries. Supernovae are connected to almost every aspect of astrophysics from star formation to cosmic ray acceleration to dust formation to chemical enrichment and feedback. Type Ia supernovae remain one of our primary dark energy probes. New classes of exotic transients are revealing rare and extreme endpoints to stellar evolution. I will discuss recent successes and potential future opportunities in transient astrophysics. These include a factor of 2 improvement in Type Ia supernova distances, a new survey to make the most headway in measuring dark energy, a large on-going Hubble program and the innovative use of light echoes from historical Galactic supernovae to measure the explosion properties of Type Ia supernovae, and a Magellan program to probe Type Ia supernova progenitor environments. I will also briefly discuss the recently identified Type Iax class of supernovae, which are the most common "peculiar" supernovae. I will present observations of the progenitor system of one Type Iax supernova, the first detection of a progenitor system for any thermonuclear supernova.