KICP Seminars & Colloquia, Spring 2017

Seminar schedule for Spring 2017
March 29, 2017
Astronomy Colloquium
Steinn Sigurdsson
Penn State
How Black Holes get their Kicks: Dynamical Evolution and Coalescence   [Abstract]
March 31, 2017
Friday noon seminar
Alessandro Manzotti
University of Chicago
Delensing CMB B-modes: results from SPT   [Abstract]
April 5, 2017
Wednesday colloquium
Juan I. Collar
University of Chicago
News from PICO and COHERENT   [Abstract | Video]
April 7, 2017
Friday noon seminar
Cosmin Deaconu
The University of Chicago
Radio-detection of Ultra-High Energy Neutrinos with the ANITA Long-Duration Balloon Payload   [Abstract]
April 11, 2017
Astronomy Tuesday Seminar
Farhad Yusef-Zadeh
Northwestern University
Star Formation Near the Supermassive Black Hole Sgr A*   [Abstract]
April 12, 2017
Astronomy Colloquium
Hsiao-Wen Chen
University of Chicago
Probing Chemical Enrichment in the Circumgalactic Medium -- Combining Absorption Spectroscopy and Direct Imaging Observations   [Abstract]
April 14, 2017
Friday noon seminar
Scott Hertel
University of Massachusetts
Superfluid 4He as a tool for sub-eV particle physics   [Abstract]
April 19, 2017
Wednesday colloquium
J. Richard Bond
Canadian Institute for Theoretical Astrophysics, University of Toronto
Observing, Mapping and Mocking our Cosmic Beginnings   [Abstract | Video]
April 21, 2017
Friday noon seminar
Michael J Baker
Johannes Gutenberg University Mainz
The Vev Flip-Flop: Dark Matter Decay between Weak Scale Phase Transitions   [Abstract]
April 24, 2017
Open Group seminar
Martina Gerbino
Oskar Klein Centre for Cosmoparticle Physics - Stockholm University
Quantifying the sensitivity of cosmological data to the neutrino mass hierarchy   [Abstract]
April 24, 2017
Open Group seminar
Massimiliano Lattanzi
Istituto Nazionale di Fisica Nucleare - Ferrara
Can secret neutrino interactions reconcile cosmology with short-baseline anomalies?   [Abstract]
April 26, 2017
Astronomy Colloquium
Nergis Mavalvala
MIT
First results from LIGO: past, present and future   [Abstract]
April 27, 2017
Open Group seminar
Titouan Lazeryas
MPA
Dark Matter Halo Bias from Separate Universe Simulations   [Abstract]
April 28, 2017
Open Group seminar
Benjamin Horowitz
UC Berkeley
Reconstruction of Cluster-Scale Cosmic Microwave Background Lensing   [Abstract]
April 28, 2017
Friday noon seminar
Antonia Hubbard
Northwestern University
Searching for Dark Matter with the Micro-X Sounding Rocket   [Abstract]
May 2, 2017
Astronomy Tuesday Seminar
Edwin Kite
UChicago GeoSci
Connecting plumes to oceans at Enceladus and Europa
May 3, 2017
Astronomy Colloquium
Erik Shirokoff
University of Chicago
Novel detectors for next-generation mm-wavelength instruments   [Abstract]
May 5, 2017
Friday noon seminar
Rebekah A Hounsell
University of California Santa Cruz
Simulations of the WFIRST Supernova Survey and Forecasts of Cosmological Constraints   [Abstract]
May 10, 2017
Astronomy Colloquium
Marc Kamionkowski
Johns Hopkins
Dust polarization and interstellar turbulence   [Abstract]
May 12, 2017
Friday noon seminar
Philip Chang
UW-Milwaukee
The Physics and Cosmology of TeV Blazars   [Abstract]
May 16, 2017
Astronomy Tuesday Seminar
Christopher Moore
University of Colorado, Boulder
Exploring solar coronal properties through soft X-ray observations of the MinXSS (Miniature X-ray Solar Spectrometer) CubeSat   [Abstract]
May 17, 2017
Wednesday colloquium
Albert Stebbins
Fermilab
Fast Radio Bursts!   [Abstract | Video]
May 19, 2017
Friday noon seminar
Victor Buza
Harvard University
Constraining Inflation Using Present and Future CMB polarization experiments: performance-based forecasts   [Abstract]
May 24, 2017
Wednesday colloquium
Camille Avestruz
University of Chicago
Automated Object Classification for Large Scale Future Surveys: A Strong Lensing Example with Machine Learning   [Abstract | Video]
May 26, 2017
Friday noon seminar
Niharika Sravan
Northwestern University
Single and binary progenitors of 'partially stripped' supernovae   [Abstract]
May 30, 2017
Astronomy Tuesday Seminar
Eduardo Banados
Carnegie Observatories
Quasars in the Epoch of Reionization   [Abstract]
May 31, 2017
Wednesday colloquium
Chihway Chang
University of Chicago
Mapping the Cosmos with the Dark Energy Survey - sneak peek of the first year weak lensing results   [Abstract | Video]
June 2, 2017
Friday noon seminar
Christopher Tunnell
University of Chicago
XENON1T results and how one can make the world's best direct dark matter detector in 5 easy steps   [Abstract]
June 9, 2017
Friday noon seminar
Julie Dumas
Vanderbilt University
Testing the Caustic Ring Dark Matter Halo Model Against Observations in the Milky Way   [Abstract]
June 16, 2017
Astronomy Special Seminar
Mitsunori Araki
Tokyo University of Science, Japan
Indications of Top-Down Chemistry by Laboratory Spectroscopy and Radio Observations   [Abstract]
 
WEDNESDAY COLLOQUIA

  • April 5, 2017 | 3:30 PM | ERC 401
    News from PICO and COHERENT
    Juan I. Collar, University of Chicago

    Video
    I will discuss the most recent results from PICO, a search for WIMP dark matter using bubble chambers, as well as future plans and some exciting lines of related research. I will then move on to cover COHERENT, an ongoing effort at ORNL's Spallation Neutron Source to detect and exploit coherent neutrino-nucleus scattering, soon to produce first results. The "glue" between these two subjects will be an elaboration on the overlap in techniques and methods used in modern neutrino and astroparticle physics. Abundant examples of this cross-talk will be provided.
  • April 19, 2017 | 3:30 PM | ERC 161
    Observing, Mapping and Mocking our Cosmic Beginnings
    J. Richard Bond, Canadian Institute for Theoretical Astrophysics, University of Toronto

    Video
    I will give my take on the phenomenology (and yes theory) of inflation as revealed in Planck and other CMB) and LSS experiments, but with an eye to the glorious CMB future of AdvACT, CCAT-p, Simons Observatory, Stage 4, and the LSS of Euclid, Chime, and much more besides that we mock. Apart from displaying linear and quadratic maps of the primordial universe, a compression of what we now know, i will chat about CMB/LSS anomalies, in practice and in theory, pointing to post-inflation chaotic dynamical systems that can lead to subdominant non-Gaussian signals unlike the ones we have put such stringent constraints on with Planck 2015; and relate everything to non-equilibrium entropies, including the formation of all cosmic structure.
  • May 17, 2017 | 3:30 PM | ERC 161
    Fast Radio Bursts!
    Albert Stebbins, Fermilab

    Video
    On a human scale most astronomical sources are large and vary slowly. They must be large enough to produce enough light be to seen at astronomical distances and the light travel time across a large source limits the timescale for observable variations. Nevertheless in recent years extremely rapidly varying radio emission has been detected and found to be a common phenomena. The most extreme case has timescales as small as one nanosecond, inferred size smaller than one meter, peak luminosity exceeding that of the Sun, and is observed at a distance of 2kpc. More numerous and further away are Fast Radio Bursts (FRBs), originating at cosmological distances, lasting a millisecond and arriving at Earth a few times a minute. These events are the brightest sources known in terms of an off-scale brightness temperature, yet the emission mechanism is undetermined. I will discuss some ideas for the origin of this emission and how these bright bursts could be used to augment gravitational wave and neutrino astronomy as well as the study of cosmological parameters and the intergalactic medium.
  • May 24, 2017 | 3:30 PM | ERC 161
    Automated Object Classification for Large Scale Future Surveys: A Strong Lensing Example with Machine Learning
    Camille Avestruz, University of Chicago

    Video
    Gravitational lensing offers a direct probe of the underlying mass distribution of lensing systems, a window to the high redshift universe, and a geometric probe of cosmological models. The advent of large scale surveys such as the Large Synoptic Sky Telescope and Euclid has prompted a need for automatic and efficient identification of strong lensing systems. We present (1) (ALL) Automated Lensing Learner, a strong lensing identification pipeline that will be publicly released as open source software, and (2) a publicly available mock LSST dataset with strong galaxy-galaxy lenses. In this first application of the pipeline, we employ a fast feature extraction method, Histogram of Oriented Gradients (HOG), to capture edge patterns that are characteristic of strong gravitational arcs in galaxy-galaxy lensing. We use logistic regression to train a supervised classifier model on the HOG of HST- and LSST-like images. Our tests demonstrate an efficient and effective method for automatically identifying strong lenses that captures much of the complexity of the arc finding problem. The linear classifier both runs on a personal laptop and can easily scale to large data sets on a computing cluster, all while using existing open source tools.
  • May 31, 2017 | 3:30 PM | ERC Auditorium 161
    Mapping the Cosmos with the Dark Energy Survey - sneak peek of the first year weak lensing results
    Chihway Chang, University of Chicago

    Image credit: Andreas Papadopoulos
    Video
    Weak gravitational lensing, or weak lensing, is one of the most powerful tools in cosmology. The technique relies on measuring accurately the shape of a large number of galaxies, and statistically translating the shape measurements into (dark matter) mass distributions. The first year data from the Dark Energy Survey (DES Y1) provides the most powerful weak lensing dataset to date. In this talk I will first give an update on the status of the cosmology analysis from DES Y1 data and present some preliminary results. Next, I will describe our work in generating and testing the wide-field weak lensing mass maps from the galaxy shape measurements and some exciting applications for the maps. I will end with thoughts on how weak lensing could also inform us on various topics of galaxy formation, which is essential for completing the story behind the Universe we see today.

 
FRIDAY NOON SEMINARS

  • March 31, 2017 | 12:00 PM | ERC 401
    Delensing CMB B-modes: results from SPT
    Alessandro Manzotti, University of Chicago

    A promising signature of cosmic inflation is the presence of a "B-mode" component in the polarization of the Cosmic Microwave Background (CMB) induced by primordial gravitational waves. For many inflation models, this B-mode signal is predicted to be at a level detectable in the near future. However current searches are limited by a "lensing B-mode" component that is produced by gravitationally lensing primordial E modes. In order to potentially detect the inflationary signal from B-mode measurements, lensing B modes must be characterized and removed in a process referred to as "delensing." This process has been studied extensively theoretically and with simulations, but has not been performed on polarization data. In this talk, I will present a demonstration of CMB B-mode delensing using polarization data from the South Pole Telescope polarimeter, SPTpol. Furthermore, using realistic simulations that include filtering and realistic CMB noise, we will show what is currently limiting the delensing efficiency and how it will rapidly improve in the near future.
  • April 7, 2017 | 12:00 PM | ERC 401
    Radio-detection of Ultra-High Energy Neutrinos with the ANITA Long-Duration Balloon Payload
    Cosmin Deaconu, The University of Chicago

    The interactions of ultra-high-energy cosmic rays with the Cosmic Microwave Background are expected to produce a flux of EeV-scale neutrinos through the GZK process. Successful detection of these cosmogenic neutrinos would help elucidate the sources of the highest-energy cosmic rays and probe the standard model in a new regime. Due to the low predicted flux and small interaction cross-section, an enormous detector is required for successful measurement. The Antarctic Impulse Transient Antenna (ANITA) long-duration balloon payload scans the Antarctic ice sheet for radio emission produced by the interactions of cosmogenic neutrinos in ice. At altitude, ANITA instantaneously instruments a volume on the order of 10^6 km^3. This talk will provide an overview of the ANITA detection technique, instrumentation, analysis methods, and results so far. I will focus on the recent fourth flight of ANITA, completed in December, as well as a strange event detected in the first ANITA flight that is potentially of neutrino origin.
  • April 14, 2017 | 12:00 PM | ERC 401
    Superfluid 4He as a tool for sub-eV particle physics
    Scott Hertel, University of Massachusetts

    Efforts to observe interactions between galactic dark matter and laboratory test particles are undergoing a transition, broadening out from the standard WIMP hypothesis. Some models newly attracting attention inhabit the keV-MeV mass range. The dominant practical challenge in probing this light mass range is the development of detector technologies sensitive to sub-eV energy depositions. I'll describe both the general challenge of this low-energy regime and also one possible technological path forward, employing meV-scale kinetic excitations of the superfluid state.
  • April 21, 2017 | 12:00 PM | ERC 401
    The Vev Flip-Flop: Dark Matter Decay between Weak Scale Phase Transitions
    Michael J Baker, Johannes Gutenberg University Mainz

    We discuss a new alternative to the Weakly Interacting Massive Particle (WIMP) paradigm for dark matter. Rather than being determined by thermal freeze-out, the dark matter abundance in this scenario is set by dark matter decay, which is allowed for a limited amount of time just before the electroweak phase transition. We discuss a concrete model which exhibits a ``vev flip-flop'' and show that it is phenomenologically successful in the most interesting regions of its parameter space. We comment on detection prospects, primarily at the LHC.
  • April 28, 2017 | 12:00 PM | ERC 401
    Searching for Dark Matter with the Micro-X Sounding Rocket
    Antonia Hubbard, Northwestern University

    The Micro-X sounding rocket uses a Transition Edge Sensor (TES) array to make X-ray observations. The improved energy resolution of TESs compared to traditional space-based X-ray detectors brings new precision to both supernova remnant observations and the X-ray search for sterile neutrino dark matter. Current X-ray observations disagree over the potential presence of a 3.5 keV X-ray line consistent with a sterile neutrino interaction, and Micro-X is in a unique position to establish or refute the presence of this line. I will present the construction status of the instrument and expectations for flight observations, with special emphasis given to the prospects of sterile neutrino studies.
  • May 5, 2017 | 12:00 PM | ERC 401
    Simulations of the WFIRST Supernova Survey and Forecasts of Cosmological Constraints
    Rebekah A Hounsell, University of California Santa Cruz

    The Wide Field InfraRed Survey Telescope (WFIRST) was the highest ranked large space-based mission of the 2010 New Worlds, New Horizons decadal survey. It is now a NASA mission in formulation with a planned launch in the mid-2020's. A primary mission objective is to precisely constrain the nature of dark energy through multiple probes, including Type Ia supernovae (SNe Ia). Within this talk I present the first realistic simulations of the WFIRST SN survey based on current hardware specifications and using open-source tools. I will review different survey strategies with varying time allocations between WFIRST's wide-field channel (WFC) imager and integral field channel (IFC) spectrometer, and predict the dark energy task force figure of merit (DETF FoM) for each strategy. Even without improvements to other cosmological probes, the WFIRST SN survey has the potential to increase the FoM by more than an order of magnitude from the current values.
  • May 12, 2017 | 12:00 PM | ERC 401
    The Physics and Cosmology of TeV Blazars
    Philip Chang, UW-Milwaukee

    The universe is teeming with very high energy gamma ray sources (> 100 GeV), but it is generally thought that their impact on the universe is minor at best. On energetic grounds, this assumption seems well-founded because the energy density in TeV photons is 0.2% of that of ionizing photons from quasars. However, as I hope to show in this talk, this is not the case. Rather, the greater efficiency by which TeV photons can be converted to heating in the intergalactic medium (IGM) allows TeV blazars dominate the heating of the IGM at low redshift. I will discuss the nature of this conversion via beam instabilities. I will then discuss how the resultant heating from these TeV sources makes dramatic differences for constraints on the intergalactic magnetic field, on the formation of structure, and on the redshift evolution of TeV blazars. I will also discuss how it gives rise to the inverted temperature-density profile of the IGM, the bimodality of galaxy clusters, and the paucity of dwarf galaxies in galactic halos and voids.
  • May 19, 2017 | 12:00 PM | ERC 401
    Constraining Inflation Using Present and Future CMB polarization experiments: performance-based forecasts
    Victor Buza, Harvard University

    A long-sought prediction of our most refined approach to early universe cosmology, the inflationary theory, is the existence of primordial gravitational waves. A potential observational signature of these waves are so called "primordial B-modes" in CMB polarization maps. However, local sources such as galactic dust and synchrotron, as well as lensing of the CMB, also produce "B-mode" signals that need to be untangled from the observed signal in order to make precise claims about the early universe. In this talk I will describe a multicomponent likelihood analysis framework for joint analyses of various CMB datasets that takes into account multiple signal types, and its subsequent use for analysis of BICEP2, Keck and Planck CMB polarization data to derive the tightest current constraints, parametrized by the tensor-to-scalar ratio, on primordial B-modes (r<0.07). I will also talk about modifying this likelihood framework into a spectral-based Fisher projection framework that allows using current achieved performances from various CMB experiments to make robust forecasts for future CMB-polarization endeavors. This approach is unique in its implementation of real-life experimental inefficiencies by using actual on-sky performance of BICEP/Keck experiments, which produced leading constraints on r, to scale to future capabilities. This framework allows for rapid iteration on how various experimental configurations affect the underlying science results. It has been extensively used in the context of optimizing survey configurations, and calculating inflation projections for the next generation experiment in the BICEP/Keck series, and the field-wide CMB-Stage 4 endeavor.
  • May 26, 2017 | 12:00 PM | ERC 401
    Single and binary progenitors of 'partially stripped' supernovae
    Niharika Sravan, Northwestern University

    The rise of survey telescopes in the past decade have led to an explosion in the number of supernovae (SNe) discovered and the amount of information available on them. They have revealed an unexpected diversity in the properties of progenitor stars and their environments. Unfortunately, theoretical efforts to explain these have lagged. However, there is a growing urgency for robust theoretical models to inform supernova (SN) observations given the imminent launch of LSST, which threatens to overwhelm current techniques for studying SNe. As a step towards addressing this vacuum, we undertake a comprehensive study of a group of 'partially stripped' SNe, known as Type IIb SNe. These are in need of theoretical interpretation because mechanisms driving significant mass loss in the progenitor stars are an open question. In this talk, I will describe single and binary progenitors of Type IIb SNe and their properties. I will present results for the application of our work to the most recent Type IIb with a detected progenitor, SN 2016gkg. In particular, we derive observational constraints for the progenitors and binary companions of SN 2016gkg that can be verified in the future.
  • June 2, 2017 | 12:00 PM | ERC 576
    XENON1T results and how one can make the world's best direct dark matter detector in 5 easy steps
    Christopher Tunnell, University of Chicago

    Within the last month, we on the XENON collaboration published our first results from the XENON1T experiment's 34.2 live day run, which is the first ton-scale detector using this world-leading technology of liquid-xenon time-projection chambers. These results do not make any claims of a dark matter signal but rather further weaken the WIMP hypothesis. In these results, which had a large contribution from the KICP XENON group, you can think of there as being a checklist of requirements needed to have strong results like ours in this competitive field. This includes rather physical requirements such as being able to contain ~3000 kg of liquid xenon at cryogenic temperatures, where I will discuss the hardware insomuch as it is of interest to cosmologists. My focus however will be on the analysis we performed, where beyond our WIMP results, we were able to establish that this detector is the quietest on earth (1.93 +/- 0.25) * 10^-4 events/(kg day keV). This allows us, when combined with novel calibration and analysis techniques, to set the strongest limits for WIMP masses above 10 GeV, with a minimum of 7.7e-47 cm^2 at 35 GeV. In explaining how we produced these results, the promising prospects for XENON1T in the coming years will become clear.
  • June 9, 2017 | 12:00 PM | ERC 401
    Testing the Caustic Ring Dark Matter Halo Model Against Observations in the Milky Way
    Julie Dumas, Vanderbilt University

    A prediction of axion dark matter models is they can form Bose-Einstein condensates and rigid caustic rings as a halo collapses in the non-linear regime. In this talk, I will present results from the first study of the caustic ring model for the Milky Way halo (Duffy & Sikivie 2008), focusing on observational consequences. I will describe the formalism for calculating the gravitational acceleration of a caustic ring halo. The caustic ring dark matter theory reproduces a roughly logarithmic halo, with large perturbations near the rings. I will show that this halo can reasonably match the known Galactic rotation curve. We explored the effects of dark matter caustic rings on dwarf galaxy tidal disruption with N-body simulations. N-body simulations of the Sagittarius (Sgr) dwarf galaxy in a caustic ring halo potential, with disk and bulge parameters that are tuned to match the Galactic rotation curve, match observations of the Sgr trailing tidal tails as far as 90 kpc from the Galactic center. Like the Navarro-Frenk-White (NFW) halo, they are, however, unable to match the leading tidal tail. None of the caustic, NFW, or triaxial logarithmic halos are able to simultaneously match observations of the leading and trailing arms of the Sagittarius stream. I will further show that simulations of dwarf galaxies that move through caustic rings are qualitatively similar to those moving in a logarithmic halo.

 
OPEN GROUP SEMINARS

  • April 24, 2017 | 10:30 AM | ERC 419
    Quantifying the sensitivity of cosmological data to the neutrino mass hierarchy
    Martina Gerbino, Oskar Klein Centre for Cosmoparticle Physics - Stockholm University

    Present measurements are not able to firmly single out nature's choice for the neutrino mass hierarchy. Consequently, in the absence of a robust measurement of the neutrino mass ordering, a desirable bound on the neutrino mass would be one which does not rely on any assumption (or, to be more precise: that relies on the less informative possible assumption) about the hierarchical distribution of the total mass among the three eigenstates. We will discuss the role of the choice of the prior when assessing the sensitivity of data to the neutrino hierarchy, and introduce a novel method to quantify the sensitivity in the context of Bayesian analysis.
  • April 24, 2017 | 11:00 AM | ERC 419
    Can secret neutrino interactions reconcile cosmology with short-baseline anomalies?
    Massimiliano Lattanzi, Istituto Nazionale di Fisica Nucleare - Ferrara

    The interpretation of anomalies in short-baseline (SBL) neutrino experiments in terms of a light (~ 1 eV mass) sterile neutrino is challenged by cosmological observations, since it implies a complete thermalization of the extra eigenstate nd thus N_eff = 4. Moreover, the neutrino mass bound from the Planck satellite strongly disfavours a mass as large as 1 eV. It has been suggested that secret neutrino interactions could allow to circumvent both issues and reconcile SBL and CMB measurements. I will discuss whether this is actually the case, taking into account the effect of secret interactions in the evolution of cosmological perturbations.
  • April 27, 2017 | 1:00 PM | ERC 445
    Dark Matter Halo Bias from Separate Universe Simulations
    Titouan Lazeryas, MPA

    The large-scale local bias parameters of dark matter halos are essential to describe the statistics of halos and galaxies on large scales, as well as for the halo model of the matter distribution. Using so-called separate universe simulations, we recently obtained precise measurements of the three leading bias parameters. For b2 and b3, these are the most precise measurements to date. We compare our results with bias parameters obtained from two and three points cross-correlation functions and with theoretical predictions from the excursion set peaks (ESP) model. Using the same set of simulations, we further investigate halo assembly bias, i.e. the dependence of the halo bias on properties other than the halo mass. We focus on several halo properties including halo concentration, spin, ellipticity and mass accretion rate and measure assembly bias for both b1 and b2. Results are in good agreement with previous studies for the linear bias. To try and better understand the physical mechanisms behind assembly bias, we also look at the joint dependence of bias on two halo properties in addition to the mass and compare our results to theoretical ones from the ESP.
  • April 28, 2017 | 11:00 AM | ERC 445
    Reconstruction of Cluster-Scale Cosmic Microwave Background Lensing
    Benjamin Horowitz, UC Berkeley

    Cluster cosmology with upcoming surveys, like CMB S-4 and the Simon's Observatory, will greatly contribute to our understanding of the universe by constraining the properties of neutrinos, understanding the formation of structure, and examining the gas properties within clusters. While there are a number of ways to gain estimates on the mass of these clusters, only gravitational lensing has the ability to measure these masses in a way that is not sensitive to the particular gas physics within the cluster. In particular, the lensing of the CMB has significant promise as it provides an image with consistent statistical properties at known redshift. However, current techniques in analyzing these lensed images are fundamentally limited by variation in the CMB gradient which should be able to precisely reconstructed on cluster scales. In this seminar, I will discuss development of more optimal methods of measuring lensing by clusters of CMB which reduce systematics and provide more accurate cluster masses on scales probed by upcoming surveys.

 
ASTRONOMY COLLOQUIA

  • March 29, 2017 | 3:30 PM | ERC 161
    How Black Holes get their Kicks: Dynamical Evolution and Coalescence
    Steinn Sigurdsson, Penn State

    Recent observations have increased interest in the possibilities of a significant population of black hole binaries in the local universe. Natal kicks may play a crucial role in the merger rate of stellar mass black holes. Dynamical evolution can lead to an enhanced interaction rate for compact binaries in dense stellar systems and a distinct and richer population of compact binaries. I discuss some of the issues related to black hole binary formation and coalescence, the issue of retention in globular clusters and possible contribution to the LIGO rate.
  • April 12, 2017 | 3:30 PM | ERC 161
    Probing Chemical Enrichment in the Circumgalactic Medium -- Combining Absorption Spectroscopy and Direct Imaging Observations
    Hsiao-Wen Chen, University of Chicago

    Tremendous progress has been made over the last decade in our empiricaland theoretical understanding of how galaxies form and evolve across cosmic time. In particular, state-of-the-art cosmological simulations can not only match the large-scale statistical properties of galaxies, but they can also successfully reproduce the observed small-scale features of star-forming disks. However, these models have fallen short in matching the empirical properties of diffuse gas, which constitutes 90% of all baryons in the universe, beyond visible galaxy disks and into circumgalactic space. An accurate characterization of the complex physical processes that govern the interactions between star-forming regions and this diffuse circumgalactic medium (CGM) is a critical next step toward a comprehensive understanding of galaxy formation and evolution. In this talk, I will summarize the progress and challenges in CGM studies from traditional absorption-line observations, and discuss future prospects in direct imaging of the CGM around distant galaxies.
  • April 26, 2017 | 3:30 PM | ERC 161
    First results from LIGO: past, present and future
    Nergis Mavalvala, MIT

    The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015. Since then there have been a couple more detections of binary black hole mergers. I will discuss the instruments that made these discoveries, the science so far, and plans for future improvements and upgrades to LIGO.
  • May 3, 2017 | 3:30 PM | ERC 161
    Novel detectors for next-generation mm-wavelength instruments
    Erik Shirokoff, University of Chicago

    The kinetic inductance detector (KID) is a novel superconducting photon detector. It offers simple fabrication, intrinsic multiplexing of thousands of detectors per cable, and much higher dynamic range than competing technologies, and has now demonstrated background limited operation suitable for ground-based instruments at mm and submm wavelengths. I'll discuss two specific applications that make use of these new devices. The first, SuperSpec, is an compact on-chip, mm-wavelength spectrometer. Its small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multi-object spectrometers able to catalog thousands of dusty star forming galaxies at high redshift. I will discuss the design, optimization, and measured performance of our prototype devices, our upcoming engineering run with the SuperSpec demonstration camera, and the unique observational opportunities accessible to future large-scale facility instruments based upon this technology. The second project, the Chicago CMB-KIDs program, is developing a KID-based, polarization sensitive, multi-band focal plane array optimized for CMB observations. I'll discuss our pixel designs and progress toward producing laboratory demonstration of a full-scale array suitable for deployment in a future CMB instrument.
  • May 10, 2017 | 3:30 PM | ERC 161
    Dust polarization and interstellar turbulence
    Marc Kamionkowski, Johns Hopkins

    Perhaps the most surprising result from the Planck satellite is the observation that the E-mode power in the dust polarization is twice that in the B mode. In this talk I will show how the E and B modes in the dust polarization are related to fluctuations in the magnetized interstellar medium. I will argue that the observed E/B ratio, as well as the TE (temperature-polarization) cross-correlation are not easily reconciled with expectations from MHD turbulence. I will then discuss some alternative explanations for the dust-emission patterns seen in the Planck temperature-polarization maps and outline some interesting directions for future related research.

 
ASTRONOMY TUESDAY SEMINARS

  • April 11, 2017 | 12:00 PM | ERC 576
    Star Formation Near the Supermassive Black Hole Sgr A*
    Farhad Yusef-Zadeh, Northwestern University

    The environment of Sgr A* provides a window to close-up study of star formation under extreme physical conditions. A critical question regarding star formation near supermassive black holes (SMBHs) is whether tidal shear in the vicinity of SMBHs is able to completely suppress star formation or induce star formation. There are currently two modes of star formation that are considered to explain the origin of young stars near Sgr A*. One is the standard cloud-based mode of star formation. The other is disk-based of star formation, which explains the disk of stars orbiting Sgr A*. I will present recent observations and discuss these modes of star formation applied to the region within 0.5 pc of Sgr A* and beyond the nuclear cluster. In addition, I will discuss a viable mechanism to explain the origin of the Fermi bubble resulting from gas accretion onto Sgr A* around the same time that young OB stars were formed near the black hole.
  • May 2, 2017 | 12:00 PM | ERC 576
    Connecting plumes to oceans at Enceladus and Europa
    Edwin Kite, UChicago GeoSci
  • May 16, 2017 | 12:00 PM | ERC 576
    Exploring solar coronal properties through soft X-ray observations of the MinXSS (Miniature X-ray Solar Spectrometer) CubeSat
    Christopher Moore, University of Colorado, Boulder

    The Solar outer atmosphere, called the corona, is filled with hot plasma exceeding a million degrees kelvin confined by magnetic fields that radiates UV and X-rays. While there is a consensus that magnetic fields are vital conduits for transporting the energy needed to heat the corona from the lower solar atmosphere, the main heating mechanisms are still in debate. Photons originating from the strongest quasi-static magnetic field structures called active regions (ARs), contain information on the local plasma temperature, density, chemical abundance and particle processes at the time of generation. Thus, soft X-rays provide unambiguous probes of hot plasma properties. The majority of solar soft X-ray observations have included spectrally integrated filter images, high spectral resolution (E/ΔE ~ 1,000) narrowband spectra, low resolution (E/ΔE ~ 10) spectral images, but limited spectrally resolved broadband observations. The Miniature X - ray Solar Spectrometer (MinXSS) 3U CubeSats developed by graduate students, professionals and professors at the University of Colorado - Boulder are designed to fill the gap in soft X - ray measurements with moderate resolving power (E/ΔE ~ 40, at 5.9 keV) over a fairly broad spectral bandpass (1 - 10 keV). The twin MinXSS CubeSats, mostly funded by NASA, can provide possibly 5 years of minimally interrupted observations of the solar soft X - ray flux to better constrain the characteristics and dynamics (especially solar flares) of coronal plasma. The MinXSS mission commenced on May 16, 2016 with the deployment of MinXSS - 1 from the International Space Station and has been operating nominally. This talk will discuss the MinXSS mission, instrument capabilities, initial science results, and the benefit of combining MinXSS observations with other solar observatories.
  • May 30, 2017 | 12:00 PM | ERC 576
    Quasars in the Epoch of Reionization
    Eduardo Banados, Carnegie Observatories

    This artist's impression shows how ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, may have looked. This quasar is the most distant yet found and is seen as it was just 770 million years after the Big Bang. This object is by far the brightest object yet discovered in the early Universe.

    Credit: ESO/M. Kornmesser
    A prime objective of observational astrophysics is to characterize the earliest sources in the first Gyr of the universe, and to peer into the cosmic times when the first stars, black holes and galaxies formed. Although galaxy candidates are now identified up to redshifts of about 10, their faintness typically precludes detailed studies of their nature, and often, even their spectroscopic confirmation. Quasars, on the other hand, are the most luminous non-transient sources known and can be studied in detail at the earliest cosmic epochs. The discovery and characterization of a statistically significant sample of quasars at z>6 is crucial to further study the epoch of reionization, one of the current frontiers of astrophysical research. I will present our efforts on building such a statistical sample, which has led to tripling the number of these quasars in just the last three years. I will discuss the diverse range of properties of this sample, the future direction for distant quasar searches, and also highlight some of the surprises revealed by our current quasar sample as well as our initial follow-up studies from optical to radio wavelengths. In particular, recent observations with ALMA revealed the presence of far-infrared companions around the quasars, and provide key constraints on the properties of the quasar host galaxies. Finally, I will also talk about exciting and encouraging findings from very recent observations.

 
ASTRONOMY SPECIAL SEMINARS

  • June 16, 2017 | 12:00 PM | ERC 545
    Indications of Top-Down Chemistry by Laboratory Spectroscopy and Radio Observations
    Mitsunori Araki, Tokyo University of Science, Japan

    After the historic discovery of C60+ in diffuse clouds, the new hypothesis, top-down chemistry (TDC), is receiving much attention in the field of astrochemistry. Unlike the ordinary bottom-up chemistry (BUC) in dense clouds which produces molecules from atoms and simple molecules by chemical synthesis, TDC produces molecules from dissociation of large molecules and dust in interstellar space. Large molecules and dust produced in circumstellar envelopes of late-type stars are transported to diffuse clouds and become the starting material of chemistry. The discovery of C60+ is a good evidence of the TDC since it is impossible to produce C60+ by BUC in the low density environment of diffuse clouds. Further proof the TDC is anticipated from laboratory experiments and astronomical observations. Recently, we observed top-down production of a linear carbon-chain molecule HC5N+ from aromatic benzonitrile in a hollow-cathode discharge in the laboratory as the first detection in discharge plasmas. At the very least, this detection suggests a reaction path from an aromatic to a linear carbon-chain molecule by TDC exists in a gas phase. In addition to laboratory study, I will present our recent results of linear carbon-chain molecules, HC3N, C7H, C6H2, etc., in molecular clouds by radio observations.