KICP Seminars & Colloquia, Current and Future
Upcoming Seminars

Seminar schedule for Current (Spring 2018) & Future Quarters
March 27, 2018
Astronomy Tuesday Seminar
Nia Imara
Harvard University
Star Formation Then and Now   [Abstract]
March 28, 2018
Wednesday colloquium
Peter Adshead
University of Illinois at Urbana-Champaign
Gauge-field inflation and the origin of the matter-antimatter asymmetry   [Abstract]
March 30, 2018
Friday noon seminar
Yuanyuan Zhang
Galaxy Cluster Cosmology with the Dark Energy Survey   [Abstract]
April 3, 2018
Astronomy Tuesday Seminar
Petros Tzeferacos
University of Chicago
Understanding turbulent dynamo and the transport of ultra-high-energy cosmic rays using laboratory plasma astrophysics experiments   [Abstract]
April 4, 2018
Wednesday colloquium
Rush D Holt
Science, Politicians, and the Public: What's the Story?   [Abstract | Video]
April 6, 2018
Friday noon seminar
Nadejda Marounina
University of Chicago
Habitability of water-rich exoplanets   [Abstract]
April 11, 2018
Wednesday colloquium
Rick Kessler
The University of Chicago
Preliminary Cosmology Results from the Dark Energy Survey Supernova Program   [Abstract | Video]
April 13, 2018
Friday noon seminar
Yacine Ali-Haimoud
New York University
Primordial Black Holes in the era of Planck and LIGO   [Abstract]
April 18, 2018
Astronomy Colloquium
Emily Rauscher
University of Michigan
Pushing the Boundaries: Expanding Possibilities for Exoplanet Atmospheric Characterization   [Abstract]
April 20, 2018
Friday noon seminar
Chi-Ting Chiang
C.N. Yang Institute for Theoretical Physics/Stony Brook University
Simulating structure formation in different environments and the applications   [Abstract]
April 20, 2018
Astronomy Special Seminar
Kimberly Ennico-Smith
Come Explore with Us!   [Abstract | PDF]
April 25, 2018
Astronomy Colloquium
Michael Gladders
University of Chicago
Strong Lensing: Lenses and Sources   [Abstract]
April 27, 2018
Friday noon seminar
John A B Mates
University of Colorado, Boulder
Microwave Multiplexing of Superconducting Sensors   [Abstract]
May 1, 2018
Astronomy Tuesday Seminar
Antonija Oklopcic
Harvard-Smithsonian Center for Astrophysics
A New Window into Atmospheric Escape in Exoplanets   [Abstract]
May 2, 2018
Astronomy Colloquium
Brian Metzger
Columbia University
The Multi-Messenger Picture of a Neutron Star Merger   [Abstract]
May 4, 2018
Friday noon seminar
Emanuela Dimastrogiovanni
Case Western Reserve University
The early Universe: preparing theory for observations   [Abstract]
May 8, 2018
Astronomy Tuesday Seminar
Jing Luan
University of California, Berkeley
DAVs: Red Edge & Outbursts   [Abstract]
May 9, 2018
Wednesday colloquium
Philip F Hopkins
California Institute of Technology
The State of Small-Scale "Crises" In Dark Matter   [Abstract | Video]
May 16, 2018
Astronomy Colloquium
Richard Ellis
University College, London
The Remarkable Assembly History of Elliptical Galaxies   [Abstract]
May 18, 2018
Friday noon seminar
Vasily Belokurov
University of Cambridge/CCA, NYC
The Progenitor of the Milky Way's Halo   [Abstract]
May 21, 2018
Astronomy Colloquium
Thomas Crawford
University of Chicago
May 23, 2018
Astronomy Colloquium
Alex Drlica-Wagner
Small Galaxies, Big Science: The Booming Industry of Milky Way Satellite Galaxies   [Abstract]
May 25, 2018
Friday noon seminar
Siavash Yasini
University of Southern California
Beyond the Boost   [Abstract]
May 30, 2018
Astronomy Colloquium
Ken Sembach
Astrophysics Flagships, Present & Future   [Abstract]
May 31, 2018
Astronomy Special Seminar
Kenneth Sembach
Space Telescope Science Institute
Focus on the Science, Not the Scientist   [Abstract]
June 1, 2018
Friday noon seminar
Lindy Blackburn
Harvard-Smithsonian CfA
Imaging supermassive black holes with the Event Horizon Telescope   [Abstract]
June 5, 2018
Astronomy Tuesday Seminar
Kathryn V. Johnston
TBA   [Abstract]
June 6, 2018
Astronomy Colloquium
Kathryn Johnston
Columbia University
June 13, 2018
Astronomy Colloquium
Vikram Dwarkadas
University of Chicago
KICP Colloquia and Astronomy & Astrophysics Colloquia: Unless otherwise noted, all talks are held in ERC 161 at 3:30 PM on Wednesdays. A reception will be held following the talk in the ERC 401 (KICP Colloquia) and in Hubble Lounge (ERC 501) (Astronomy & Astrophysics Colloquia).

  • March 28, 2018 | 3:30 PM | ERC 401 | Wednesday colloquium
    Gauge-field inflation and the origin of the matter-antimatter asymmetry
    Peter Adshead, University of Illinois at Urbana-Champaign

    The basic inflationary paradigm is in good shape. On the one hand, the observed density fluctuations are adiabatic, gaussian and are red-tilted---characteristics in general agreement with simple models built from scalar fields. On the other hand, B-mode polarization of the cosmic microwave background sourced by primordial gravitational waves, the so-called smoking-gun signature of inflation, remains elusive. Upcoming and planned experiments will make increasingly precise B-mode measurements, potentially putting the inflationary paradigm through a stringent test. In this talk, I describe a new class of inflationary scenarios which utilize gauge fields to generate inflationary dynamics in the early universe. Beyond simply providing yet another model for inflation, these scenarios furnish unique observational imprints which distinguish them from standard scalar-field scenarios. In particular, these scenarios generically result in large-amplitude, chiral gravitational waves and provide counterexamples to the standard claim that an observable tensor-to-scalar ratio requires inflation at the grand unification scale, as well as super-Planckian excursions of the inflaton. In addition I discuss how these chiral gravitational waves may be responsible for the matter-antimatter asymmetry of the Universe.
  • April 4, 2018 | 3:30 PM | ERC 161 | Wednesday colloquium
    Science, Politicians, and the Public: What's the Story?
    Rush D Holt, AAAS

    With many public decisions being made on the basis of political partisanship rather than scientific evidence, what storyline should scientists follow and what difference does it make for the practicing researcher?
  • April 11, 2018 | 3:30 PM | ERC 161 | Wednesday colloquium
    Preliminary Cosmology Results from the Dark Energy Survey Supernova Program
    Rick Kessler, The University of Chicago

    We have recently completed 5 seasons of the Dark Energy Survey (DES), and cosmology results starting coming out last summer. Here I will discuss new cosmology results based on a subset of spectroscopically confirmed SNIa, and describe advances in the analysis aimed for much larger samples in DES and beyond. Finally, I will briefly describe other science projects using the DES transient-search pipeline.
  • April 18, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Pushing the Boundaries: Expanding Possibilities for Exoplanet Atmospheric Characterization
    Emily Rauscher, University of Michigan

    With the launch of NASA's Transiting Exoplanet Survey Satellite, the (eventual) launch of the James Webb Space Telescope, and the continual development of ground-based capabilities and construction of extremely large telescopes, we have an expanding ability to collect atmospheric data on many more exoplanets, and much more highly detailed data on the brightest ones. The biggest, brightest transiting planets will always be hot Jupiters which, although we have been observing and modeling their atmospheres for over a decade, remain far from a "solved problem". I will discuss two types of observational techniques that can provide new, highly detailed information about their atmospheres: high-resolution spectroscopy, which provides direct measurement of a planet's rotation rate and wind speeds, and eclipse mapping, which resolves a two-dimensional image of the planet's day side. Each of these methods will enable us to tackle outstanding scientific questions. Then, as we are increasingly able to perform atmospheric characterization measurements of more diverse types of exoplanets, we will be better able to understand atmospheric and planetary properties writ large. I will provide the example of what new things we will learn from studying "warm Jupiters", just slightly out beyond the standard hot Jupiter population.
  • April 25, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Strong Lensing: Lenses and Sources
    Michael Gladders, University of Chicago

    I will discuss recent studies of both strongly lensed sources, and the foreground lens population (primarily groups and cluster of galaxies), framed by an overview of where I think the strong lensing research is headed in the next decade. The lensed sources I will detail are primarily selected from the SDSS. Highlights will include the smallest star-forming features ever resolved in a distant galaxy, the new MEGaSaURA atlas of moderate resolution rest-UV spectra of more than a dozen bright lensed galaxies at 1.7<z<3.6, and recent HST observations of Lyman continuum photons from a distant galaxy. I will also detail an extensive program to test whether the observed strong lensing by massive clusters - particularly that from the South Pole Telescope cluster sample - is consistent with theoretical expectations.
  • May 2, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    The Multi-Messenger Picture of a Neutron Star Merger
    Brian Metzger, Columbia University

    On August 17 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. Within 2 seconds of the merger, a weak burst of gamma-rays was discovered by the Fermi and INTEGRAL satellites. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 130 Million light years. The properties of the optical transient match remarkably well predictions for "kilonova" emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by rapid neutron capture nucleosynthesis (r-process). The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet (or a shock-heated "cocoon" produced as the jet interacts with the kilonova ejecta). I will describe efforts to create a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars (particularly their uncertain radii and maximum mass, which are determined by the equation of state of dense nuclear matter). Time permitting, I will preview the upcoming era of multi-messenger astronomy, once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks.
  • May 9, 2018 | 3:30 PM | ERC 161 | Wednesday colloquium
    The State of Small-Scale "Crises" In Dark Matter
    Philip F Hopkins, California Institute of Technology

    The most fundamental unsolved problems in star and galaxy formation revolve around "feedback" from massive stars (and black holes). I'll review how new generations of theoretical models combine new numerical methods and physics, to try to realistically model the diverse physics of the ISM, star formation, and feedback, on a wide range of scales from those of individual proto-stars to the inter-galactic medium. Feedback produces galactic outflows and perturbs galactic structure in ways which fundamentally perturb the nature of dark matter cores and 'cusps', re-shaping rotation curves and suppressing the central densities of low-mass galaxies. I'll discuss a variety of small-scale "crises" in cold dark matter models: "cusp-core," "missing satellites," "too big to fail," and more, and show that these "crises" tend to simply vanish as higher resolution and more treatments of known physics are included in simulations. However, I will show that there are robust, testable predictions of CDM as compared to other models such as self-interacting or ultra-light scalar field or "warm" dark matter, but these may require fundamentally new observations.
  • May 16, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    The Remarkable Assembly History of Elliptical Galaxies
    Richard Ellis, University College, London

    Once considered the simplest morphological class with smooth surface brightness profiles and homogenous old stellar populations, elliptical galaxies continue to reveal surprises. I will present the results of several comprehensive spectroscopic campaigns of what are considered to be the precursors of present-day ellipticals seen at redshifts up to and beyond 2. Good signal to noise absorption line spectra are capable of probing the stellar kinematics and stellar populations in early examples providing valuable insight into the assembly history of passive galaxies. I will discuss several puzzles that have emerged from such data including how the compact precursors (or "red nuggets") grew in physical size but hardly in stellar mass, and why early massive examples display rapidly rotating stellar disks in contrast with local examples.
  • May 21, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Thomas Crawford, University of Chicago
  • May 23, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Small Galaxies, Big Science: The Booming Industry of Milky Way Satellite Galaxies
    Alex Drlica-Wagner, Fermilab

    The small satellite galaxies of our Milky Way are the most ancient, most metal-poor, and most dark-matter-dominated systems known. These extreme objects offer a unique opportunity to test the standard model of cosmology, while also providing insights into the formation of galaxies, stars, and the heavy elements. Over the past three years, the unprecedented sensitivity of the Dark Energy Camera has allowed us to double the known population of ultra-faint Milky Way satellites. I will discuss recent results, outstanding questions, and upcoming advances in the study of the Milky Way's dark companions.
  • May 30, 2018 | 3:30 PM | ERC 401 | Astronomy Colloquium
    Astrophysics Flagships, Present & Future
    Ken Sembach, STScI

    Note: Refreshments served at 4:30 PM, Hubble Lounge

    NASA's Great Observatories have revolutionized our understanding of the Universe. The James Webb Space Telescope will continue this legacy, and together with the Hubble Space Telescope and Wide-Field Infrared Telescope will usher in an era of unprecedented information about astronomical objects ranging from Solar System objects to the first stars and galaxies formed near the beginning of time. As we continue to explore, new questions arise. Are there Earth-like planets orbiting other stars, and if so are they capable of supporting life? What secrets does the ultra-faint universe hide from our view? What is the nature of dark matter and dark energy? Future flagship missions offer great promise for answering such questions. In this talk, I'll offer some perspectives, both scientific and programmatic, on possible paths forward and the importance of truly ambitious space observatories to the future of astrophysics research.
  • June 6, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Kathryn Johnston, Columbia University

    Note: Refreshments served at 4:30 PM, Hubble Lounge
  • June 13, 2018 | 3:30 PM | ERC 161 | Astronomy Colloquium
    Vikram Dwarkadas, University of Chicago

    Note: Refreshments served at 4:30 PM, Hubble Lounge

KICP Friday noon seminar: Unless otherwise noted, all talks are held in ERC 401 at Noon on Fridays.

  • March 30, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Galaxy Cluster Cosmology with the Dark Energy Survey
    Yuanyuan Zhang, Fermilab

    Constraining LambdaCDM cosmology with galaxy cluster abundance is one of the fundamental goals of the Dark Energy Survey (DES). Many thousands of clusters out to redshift 0.65 have been identified in DES data. Weak lensing and multi-wavelength studies with X-ray and cosmic microwave background observations are performed to provide inputs to the cosmology analysis. A cosmology pipeline that considers various systematic effects such as cluster projections and mis-centering is used to derive constraints on LambdaCDM cosmology parameters. In this talk, I will present current progress on DES galaxy cluster cosmology analyses as well as discuss future improvements.
  • April 6, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Habitability of water-rich exoplanets
    Nadejda Marounina, University of Chicago

    Planets with global water oceans have been the subject of intrigue both in Hollywood and in the exoplanet community. Water worlds are water-rich exoplanets that possess >1% of water by mass, and if located at an appropriate orbital separation from their host star, they may host a global surface water ocean. These habitable (liquid ocean-bearing) water worlds are especially timely because 1) water worlds formed from remnant cores of evaporated mini-Neptunes could be one of the dominant formation mechanisms for volatile-rich habitable zone planets around M dwarf stars, and 2) their larger sizes relative to terrestrial planets make them more amenable to observations with current and upcoming telescopes such as Hubble Space Telescope (HST) and James Webb Space Telescope (JWST). The recent and exciting discovery of TRAPPIST-1 system, that may possess planets with a substantial water/ice fraction, further motivates the study of water-worlds. In the first part of this talk, I propose to give an overview on the habitability of water-worlds and show you that the the classical estimation of the habitable zone does not apply to this type of exoplanets. In the second part of my talk, I will present the coupled models of planet interiors, clathrate formation, liquid-vapor equilibrium, and atmospheric radiative transfer that are used constrain the atmospheric abundance of CO2 and corresponding habitable zone boundaries of water world exoplanets.
  • April 13, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Primordial Black Holes in the era of Planck and LIGO
    Yacine Ali-Haimoud, New York University

    LIGO's first direct gravitational-wave detections have revived interest in an old dark-matter candidate, primordial black holes (PBHs). In this talk I will first discuss cosmic microwave background constraints to PBHs in the range of ~10 to a few hundred solar masses. I will then discuss PBH binary formation processes and the resulting merger rates. In particular, I will argue that LIGO may already set the most stringent limits on PBH abundance, provided PBH binaries formed in the early Universe are not strongly perturbed by tidal fields due to non-linear structures.
  • April 20, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Simulating structure formation in different environments and the applications
    Chi-Ting Chiang, C.N. Yang Institute for Theoretical Physics/Stony Brook University

    The observables of the large-scale structure such as galaxy number density generally depends on the density environment (of a few hundred Mpc). The dependence can traditionally be studied by performing gigantic cosmological N-body simulations and measuring the observables in different density environments. Alternatively, we perform the so-called "separate universe simulations", in which the effect of the environment is absorbed into the change of the cosmological parameters. For example, an overdense region is equivalent to a universe with positive curvature, hence the structure formation changes accordingly compared to the region without overdensity. In this talk, I will introduce the "separate universe mapping", and present how the power spectrum and halo mass function change in different density environments, which are equivalent to the squeezed bispectrum and the halo bias, respectively. I will then discuss the extension of this approach to inclusion of additional fluids such as massive neutrinos. This allows us to probe the novel scale-dependence of halo bias and squeezed bispectrum caused by different evolutions of the background overdensities of cold dark matter and the additional fluid. Finally, I will present one application of the separate universe simulations to predict the squeezed bispectrum formed by small-scale Lyman-alpha forest power spectrum and large-scale lensing convergence, and compare with the measurement from BOSS Lyman-alpha forest and Planck lensing map.
  • April 27, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Microwave Multiplexing of Superconducting Sensors
    John A B Mates, University of Colorado, Boulder

    Superconducting detectors provide by far the most sensitive measurement of long-wavelength radiation for astronomy and cosmology, with detector noise falling below that of the astronomical signals in the mid-to-late 1990s, depending on the wavelength of interest. To measure better and faster, we have therefore assembled cameras with increasingly large arrays of detectors. Since the 90s, the size of superconducting detector arrays has followed a Moore's Law trend, which is set to continue into the 100,000 pixel range with instruments like the Simons Observatory and CMB-S4. Perhaps the greatest challenge to continuing this trend is the need to bring the signals from the detector arrays out of a 100 mK cryostat on a much smaller number of wires. I will present the emerging technique of multiplexing these superconducting sensors using superconducting microresonators. We can use this new scheme with both superconducting Transition-Edge Sensors (TESs) and Microwave Kinetic Inductance Detectors (MKIDs) to read out thousands of highly-sensitive detectors per coaxial cable. This capability will enable new instruments for astronomy and precision cosmology.
  • May 4, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    The early Universe: preparing theory for observations
    Emanuela Dimastrogiovanni, Case Western Reserve University

    I will describe some interesting scenarios for the generation of gravitational waves from inflation and their characteristic imprints, which can be tested with upcoming B-mode observations as well as with interferometers. In the second part of my talk I provide an overview of the physics of CMB spectral distortions and discuss what we can learn from those about the early universe.
  • May 18, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    The Progenitor of the Milky Way's Halo
    Vasily Belokurov, University of Cambridge/CCA, NYC

    We map the composition of the Galactic stellar halo in 7 dimensions spanned by phase-space coordinates and chemical abundances. The local halo appears to be dominated by stars on highly eccentric orbits. These stars are more metal-rich than typically assumed for the Galactic halo and were likely deposited into the Milky Way during an ancient massive accretion event. Using numerical simulations of the stellar halo formation we deduce that this merger must have happened between 8 and 11 Gyrs ago, during the epoch of the Galactic disk formation. This formation scenario for the MW halo has a number of implications for the studies of the evolution of the Galaxy in general and the measurements of the local Dark Matter matter distribution in particular.
  • May 25, 2018 | 12:00 PM | ERC 401 | Friday noon seminar
    Beyond the Boost
    Siavash Yasini, University of Southern California

    Our peculiar motion with respect to the cosmic microwave background (CMB) changes the observed frequency and incoming angle of the CMB photons due to the Doppler and aberration effects. The most prominent signature of these motion-induced effects on the CMB is a kinematic dipole, which is observationally indistinguishable from any intrinsic dipole that the CMB might possess. Due to this degeneracy -- and the fact that we theoretically expect the intrinsic dipole of the CMB to be subdominant with respect to the kinematic component -- the 3mK dipole of the CMB is commonly interpreted as an entirely kinematic effect. Consequently, the frame in which the entire dipole of the CMB vanishes is customarily defined as the CMB rest frame. However, if the intrinsic dipole of the CMB is non-zero, this definition would not be appropriate anymore, unless we can properly separate the intrinsic and kinematic components of the dipole. In this talk, I will demonstrate how we can achieve this goal using spectral measurements of the monopole and quadrupole moments of the CMB. I will also describe the impact of the Doppler and aberration effects on the CMB power spectrum (especially on the small angular scales) and their relevance as an observational bias for the current and future surveys. Our recently developed "Generalized Doppler and Aberration Kernel" formalism can be used to measure and remove the motion-induced effects from any arbitrary frequency-dependent cosmological observable.
  • June 1, 2018 | 12:00 PM | ERC 576 (Note Location Change for this Seminar) | Friday noon seminar
    Imaging supermassive black holes with the Event Horizon Telescope
    Lindy Blackburn, Harvard-Smithsonian CfA

    The Event Horizon Telescope is an expanding global array of sub-mm radio telescopes designed to directly probe the spacetime geometry and radiative processes on event-horizon scales for the supermassive black holes at the center of our galaxy, Sgr A*, and at the center of M87. A major goal of the EHT is to measure the size and shape of the black hole "shadow," a characteristic signature of strong lensing at the event-horizon and a fundamental prediction of general relativity. In 2017, the EHT operated an 8-station array with both the South Pole Telescope and the ALMA array in Chile for the first time, and included a coordinated campaign of simultaneous ground and space-based multiwavelength observations. While analysis is ongoing, the data achieve an unprecedented 20 micro-arcsecond resolution and provide a direct view of the spatial structure of dynamical processes in the immediate vicinity of Sgr A*.



KICP's Thunch: KICP Cosmology Lunch (Thunch) Weekly on Thursdays, Noon, ERC 401A.

Please join us for an informal lunch discussion, led by KICP fellows, of recent news and papers in cosmology. Topics range from experiment and observations to theory in all areas of KICP science. To submit or view papers for this week's Thunch please visit the Thunch website.


  • March 27, 2018 | 12:00 PM | ERC 576 | Tuesday Seminar
    Star Formation Then and Now
    Nia Imara, Harvard University

    Stars are of fundamental importance to astronomy, and how they form and shape their environments influence everything from exoplanet studies to cosmology. Stars form in heavily obscured molecular clouds, and understanding the initial conditions of star formation persists as one of the leading challenges of contemporary astrophysics. A major challenge is the wide range of physical scales involved: from the large-scale galactic environment, to molecular clouds, to the high-density filaments and cores most directly associated with the birth of stars, and all the way down to the physics of dust, atoms and molecules. I will discuss ways to overcome these challenges, focusing on the birth of molecular clouds from the atomic interstellar medium, the role of high-density substructure in the formation of stars, and the properties of molecular clouds in dwarf galaxies. I will also consider some cosmological implications of stardust, including how intergalactic dust may be a significant source of contamination in CMB spectral distortions. Throughout this presentation, I will promote the idea that bridging local star formation, extragalactic star formation, and star formation in the cosmological context will help to advance this exciting field.
  • April 3, 2018 | 12:00 PM | ERC 576 | Tuesday Seminar
    Understanding turbulent dynamo and the transport of ultra-high-energy cosmic rays using laboratory plasma astrophysics experiments
    Petros Tzeferacos, University of Chicago

    The ubiquity of cosmical magnetic fields is revealed by diffuse radio-synchrotron emission and Faraday rotation observations. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of observable matter in the Universe and regulators of the trajectories that cosmic rays follow. The standardmodel for the origin of intergalactic magnetic fields is through the amplification of seed fields via turbulent dynamo to levels consistent with current observations. We have conceived and conducted a series of high-power laser experiments at Omega, NIF, and LMJ to study the dynamo amplification of magnetic fields in different plasma regimes. The properties of the fluid and the magnetic field turbulence are characterized using a comprehensive suite of plasma and magnetic field diagnostics. In this talk, we describe the large-scale 3D simulations we performed with the radiation-MHD code FLASH on ANL's Mira to help design and interpret the experiments. We then discuss the results of the experiments we carried out at the world's largest laser facilities, which indicate that magnetic Reynolds numbers above the expected dynamo threshold are achieved and that seed magnetic fields - produced by the Biermann battery mechanism - are amplified by turbulent dynamo. We also show how these experiments can provide experimental constrains on how cosmic rays diffuse through astrophysical magnetized turbulence.
  • May 1, 2018 | 12:00 PM | ERC 576 | Tuesday Seminar
    A New Window into Atmospheric Escape in Exoplanets
    Antonija Oklopcic, Harvard-Smithsonian Center for Astrophysics

    Atmospheric escape, or mass loss, is an important process in the evolution of planetary atmospheres in the Solar System, as well as in extrasolar planets. However, there are many aspects of atmospheric escape in exoplanets that remain poorly understood, in part due to a small number of direct observations. Observational evidence of atmospheric escape has been obtained only for a few exoplanets to date, mostly through transit observations in the hydrogen Lyman-alpha line, inaccessible for ground-based observations. The absorption line of helium at 10830 Angstrom can overcome some of the main difficulties associated with the UV diagnostics. In this talk, I will present a new model of escaping planetary atmospheres used to predict in-transit absorption at 10830 Angstrom. Our results indicate that significant absorption at this wavelength can be expected in some exoplanets. The helium 10830 Angstrom line is accessible for ground-based observations using high-resolution spectrographs, which could enable more detailed studies of extended atmospheres for a much larger number of exoplanets than realistically possible with UV spectroscopy. By opening up this new wavelength window into escaping atmospheres, we can improve our understanding of the physical processes that drive atmospheric mass loss and, consequently, affect planetary evolution and demographics of planetary systems.
  • May 8, 2018 | 12:00 PM | ERC 576 | Tuesday Seminar
    DAVs: Red Edge & Outbursts
    Jing Luan, University of California, Berkeley

    As established by ground based surveys, white dwarfs with hydrogen atmospheres pulsate as they cool across the temperature range, 12,500 K < Teff < 10,800 K. Known as DAVs or ZZ Ceti stars, their oscillations are attributed to overstable g-modes excited by convective driving. The effective temperature at the blue edge of the instability strip is slightly lower than that at which a surface convection zone appears. The temperature at the red edge is a two-decade old puzzle. Recently, the Kepler space telescope discovered a number of cool DAVs exhibiting sporadic outbursts separated by days, each lasting several hours, and releasing ~10^33-10^34 erg. We provide quantitative explanations for both the red edge and the outbursts. The minimal frequency for overstable modes rises abruptly near the red edge. Although high frequency overstable modes exist below the red edge, their photometric amplitudes are generally too small to be detected by ground based observations. Nevertheless, these overstable parent modes can manifest themselves through nonlinear mode couplings to damped daughter modes which generate limit cycles giving rise to photometric outbursts.
  • June 5, 2018 | 12:00 PM | ERC 576 | Tuesday Seminar
    Kathryn V. Johnston,

    Columbia University


  • April 20, 2018 | 1:00 PM | ERC 576 | Special Seminar
    Come Explore with Us!
    Kimberly Ennico-Smith, NASA

    SOFIA is entering a new era of research and capability with significant new opportunities! From funding of $10,000 per hour of award observation time, to a multi-million dollar call for new groundbreaking science programs that can require updates to existing instruments or the fabrication of new instruments, there are a number of new ways to explore with the SOFIA team. This short meeting is a chance to review those funded opportunities and to learn about the new ideas you have for SOFIA. Please join us this Friday at 1PM!
  • May 31, 2018 | 12:00 PM | ERC 501 - Hubble Lounge | Special Seminar
    Focus on the Science, Not the Scientist
    Kenneth Sembach, Space Telescope Science Institute

    Biases can play a subtle but important role in defining the outcomes of proposal peer reviews, job hiring campaigns, and manuscript reviews. In this seminar I'll describe some of the biases discovered in the proposal review process for the Hubble Space Telescope, as well as actions being taken to minimize them including anonymization of the proposers' identities during the reviews. While widely regarded as a more objective form of peer review in many fields, science reviews with hidden proposer identities are new to the field of astronomy. Proposers will face changes in the ways proposals need to be written to prevent self-identification, and reviewers will need to be cautious not to impart conscious bias into the review process by trying to determine the identities of the proposers from the information presented. This significant change in assessing Hubble proposals will be watched closely as a "pilot program" for other observatories and agencies to emulate. After describing the path forward for Hubble, we will have an open discussion about measuring progress and the pros and cons of focusing the proposal peer review process on the science proposed rather than the proposing scientists.