Colloquia
Colloquia: Astronomy & Astrophysics colloquia and KICP colloquia - Usually Wednesdays, 3:30 PM, ERC 161, unless otherwise specified. Reception starts at 4:30 PM in Hubble Lounge (Astronomy & Astrophysics colloquia) and ERC 401 (KICP colloquia). Persons with a disability who believe they may need assistance, please call the departmental secretary in advance at 773-702-8203 or email deptsecoddjob.uchicago.edu.

Current & Future Colloquia
DateTalk TitleSpeaker
April 25, 2018
Astronomy Colloquium
Strong Lensing: Lenses and SourcesMichael Gladders, University of Chicago
May 2, 2018
Astronomy Colloquium
The Multi-Messenger Picture of a Neutron Star MergerBrian Metzger, Columbia University
May 9, 2018
KICP Colloquium
The State of Small-Scale "Crises" In Dark MatterPhilip F Hopkins, California Institute of Technology
May 16, 2018
Astronomy Colloquium
The Remarkable Assembly History of Elliptical GalaxiesRichard Ellis, University College, London
May 23, 2018 cancelled
KICP Colloquium
The Simons ObservatoryBrian Keating, UC San Diego
May 30, 2018
Astronomy Colloquium
TBAKen Sembach, STScI
June 6, 2018
Astronomy Colloquium
TBAKathryn Johnston, Columbia University

Past Colloquia
DateTalk TitleSpeaker
April 18, 2018
Astronomy Colloquium
Pushing the Boundaries: Expanding Possibilities for Exoplanet Atmospheric CharacterizationEmily Rauscher, University of Michigan
April 11, 2018
KICP Colloquium
Preliminary Cosmology Results from the Dark Energy Survey Supernova ProgramRick Kessler, The University of Chicago
April 4, 2018
KICP Colloquium
Science, Politicians, and the Public: What's the Story?Rush D Holt, AAAS
March 28, 2018
KICP Colloquium
Gauge-field inflation and the origin of the matter-antimatter asymmetryPeter Adshead, University of Illinois at Urbana-Champaign
March 14, 2018
KICP Colloquium
Dark Matter in the UniverseKatherine Freese, University of Michigan
March 7, 2018
Astronomy Colloquium
Origins of Super-Earths in Inner Solar SystemsBekki Dawson, Pennsylvania State University
February 28, 2018
Astronomy Colloquium
Heavy element synthesis in the UniverseEnrico Ramirez-Ruiz, University of California, Santa Cruz
February 21, 2018
KICP Colloquium
Discovering the Highest Energy Neutrinos Using a Radio Phased ArrayAbby Vieregg, The University of Chicago
February 14, 2018
Astronomy Colloquium
Galactic Winds: Phenomenology, Physics, and ImplicationTim Heckman, Johns Hopkins University
February 7, 2018 cancelled
KICP Colloquium
Gauge-field inflation and the origin of the matter-antimatter asymmetryPeter Adshead, University of Illinois at Urbana-Champaign
January 31, 2018
Astronomy Colloquium
The Basis for Cosmic Ray FeedbackEllen Zweibel, University of Wisconsin-Madison
January 24, 2018
KICP Colloquium
Citizen Science Frontiers: Efficiency, Engagement, and Serendipitous Discovery with Human-Machine SystemsLaura Trouille, The Adler Planetarium and Northwestern University
January 17, 2018
Astronomy Colloquium
WFIRST: Where Things Stand with the First Exoplanet Direct Imaging Flight MissionMaggie Turnbull, SETI
January 10, 2018
KICP Colloquium
From Emergent Gravity to Dark Energy and Dark MatterErik P. Verlinde, University of Amsterdam

From Emergent Gravity to Dark Energy and Dark Matter
January 10, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Erik P. Verlinde, University of Amsterdam

Video
The observed deviations from the laws of gravity of Newton and Einstein in galaxies and clusters can logically speaking be either due to unseen dark matter or due to a change in the way gravity works. Until recently there was little reason to doubt that general relativity correctly describes gravity in these circumstances. In the past few years insights from black hole physics and string theory have lead to a new theoretical framework in which the gravitational laws are derived an underlying microscopic quantum description of spacetime. An essential ingredient in the derivation of the Einstein equations is that the quantum entanglement of the vacuum obeys an area law, a condition that is known to hold in Anti-de Sitter space. In a Universe that is dominated by positive dark energy, like de Sitter space, the microscopic entanglement entropy contains, in addition to the area law, a volume law contribution whose total contribution equals the Bekenstein-Hawking entropy associated with the cosmological horizon. We will argue that this extra volume law contribution leads to modifications in the emergent laws of gravity, and provide evidence for the fact that these modifications explain the observed phenomena in galaxies and clusters currently attributed to dark matter. We end with a discussion of the possible implications for early cosmology, the CMB and structure formation.

WFIRST: Where Things Stand with the First Exoplanet Direct Imaging Flight Mission
January 17, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
Click on the image to enlarge
Maggie Turnbull, SETI

The WFIRST mission will be the first demonstration of exoplanet coronagraphy in space, and is intended to demonstrate several key technologies that are on the critical path to larger missions that will eventually find and spectrally characterize planets that could be habitable to life as we know it. WFIRST entered Phase A in January of 2016, and is expected to enter Phase B in April of this year. This talk will describe the entertaining story of how this mission came to be, where things currently stand in terms of predicted imaging performance, the potential for a starshade rendezvous mission, and what to expect for guest observer opportunities. I'll also describe how the two coronagraph science teams are working to maximize the scientific output of what is categorized as a "technology demonstration" instrument. Finally, I'll offer some of my personal take-aways from the experience of watching such a large and challenging mission come together.

Citizen Science Frontiers: Efficiency, Engagement, and Serendipitous Discovery with Human-Machine Systems
January 24, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Laura Trouille, The Adler Planetarium and Northwestern University

Video
The Zooniverse is the world's largest and most successful scientific crowdsourcing platform, engaging more than 1.6 million volunteers in tasks including classifying galaxies, discovering planets, transcribing artist's notebooks, and tracking resistance to antibiotics. Processing our increasingly large datasets poses a bottleneck for producing real scientific outcomes. Citizen science - engaging the public in research - provides a solution, particularly when coupled with machine learning algorithms and sophisticated task allocation. Faced with a rapidly growing demand for citizen science projects, Zooniverse launched its 'Project Builder' which allows you, the researcher, to build your own project in-house for free using the Zooniverse infrastructure and tools. In this talk I will discuss the frontiers of citizen science, including Zooniverse innovations in human-machine integration coupled with community engagement -- and the related open questions. I will also provide a brief tutorial on building your own crowdsourcing project.

The Basis for Cosmic Ray Feedback
January 31, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
Click on the image to enlarge
Ellen Zweibel, University of Wisconsin-Madison

There is strong observational and theoretical evidence that star formation in galaxies is inherently self limiting, and that the interaction of galaxies with their environments plays a significant role in galactic evolution. Cosmic rays - the relativistic particles that pervade our galaxy and account for about 1/3 of the energy density in the interstellar medium - have emerged as a likely agent of these forms of feedback. The basis of cosmic ray feedback is scattering of cosmic rays by plasma waves, a microscale process that ultimately transfers energy and momentum between cosmic rays and thermal gas. The image, from Ruszkowski, Yang, & Zweibel 2017, shows a simulation of an outflow driven from a galaxy by this process.

Gauge-field inflation and the origin of the matter-antimatter asymmetry
February 7, 2018 cancelled | ERC 161 | 3:30 PM | KICP Colloquium
Peter Adshead, University of Illinois at Urbana-Champaign

CANCELLED

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.

Galactic Winds: Phenomenology, Physics, and Implication
February 14, 2018 | ERC 161 | 3:30 PM | Host: Hsiao-Wen Chen | Astronomy Colloquium
Click on the image to enlarge
Tim Heckman, Johns Hopkins University

I will discuss the nature of galactic winds driven by the energy and momentum supplied by populations of massive stars. I will give an overview of the basic physical processes that lead to the formation and propagation of galactic winds. I will then give a "guided tour" of the multi-phase galactic wind driven by the prototypical starburst galaxy M 82. Next, I will describe how the basic parameters of winds can be inferred from the data and summarize the systematic dependences of these parameters on the key properties of the galaxy and the starburst. I will then discuss how well these systematic properties compare to assumptions used in cosmological simulations of galaxy evolution. Finally, I will describe the implications of winds for galaxy evolution, specifically in the context their impact on the circum-galactic medium and on the chemical evolution of galaxies.

Discovering the Highest Energy Neutrinos Using a Radio Phased Array
February 21, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Abby Vieregg, The University of Chicago

Video
Ultra-high energy neutrino astronomy sits at the boundary between particle physics and astrophysics. The detection of high energy neutrinos is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth. IceCube has detected astrophysical neutrinos at lower energies, but the best limit to date on the flux of ultra-high energy neutrinos comes from the ANITA experiment, a NASA balloon-borne radio telescope designed to detect coherent radio Cherenkov emission from cosmogenic ultra-high energy neutrinos. The future of high energy neutrino detection lies with ground-based radio arrays, which would represent an large leap in sensitivity. I will discuss a new radio phased array design that will improve sensitivity enormously and push the energy threshold for radio detection down to overlap with the energy range probed by IceCube.

Heavy element synthesis in the Universe
February 28, 2018 | ERC 161 | 3:30 PM | Host: Hsiao-Wen Chen | Astronomy Colloquium
Click on the image to enlarge
Enrico Ramirez-Ruiz, University of California, Santa Cruz

The source of about half of the heaviest elements in the Universe has been a mystery for a long time. Although the general picture of element formation is well understood, many questions about the nuclear physics processes and particularly the astrophysical details remain to be answered. Here I focus on recent advances in our understanding of the origin of the heaviest and rarest elements in the Universe.

Origins of Super-Earths in Inner Solar Systems
March 7, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
Origins of Super-Earths in Inner Solar Systems
Click on the image to enlarge
Bekki Dawson, Pennsylvania State University

Over the past decade, exoplanet surveys have discovered that many other solar systems teem with super-Earths on sub-Mercury orbits. A major open question is whether these super-Earths formed on their observed close-in orbits or formed at a wider separations and migrated in. I will present recent work on what the orbital and compositional properties of super-Earths in inner solar systems can reveal about super-Earths' origins and more generally about the physical processes driving the formation and evolution of planetary systems.

Dark Matter in the Universe
March 14, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Katherine Freese, University of Michigan

Video
"What is the Universe made of?" This question is the longest outstanding problem in all of modern physics, and it is one of the most important research topics in cosmology and particle physics today. The bulk of the mass in the Universe is thought to consist of a new kind of dark matter particle, and the hunt for its discovery in on. I'll start by discussing the evidence for the existence of dark matter in galaxies, and then show how it fits into a big picture of the Universe containing 5% atoms, 25% dark matter, and 70% dark energy. Neutrinos only constitute ½% of the content of the Universe, but much can be learned about neutrino properties from cosmological data. Leading candidates for the dark matter are Weakly Interacting Massive Particles (WIMPs), axions, and sterile neutrinos. WIMPs are a generic class of particles that are electrically neutral and do not participate in strong interactions, yet have weak-scale interactions with ordinary matter. There are multiple approaches to experimental searches for WIMPS: at the Large Hadron Collider at CERN in Geneva; in underground laboratory experiments; with astrophysical searches for dark matter annihilation products, and upcoming searches with the James Webb Space Telescope for Dark Stars, early stars powered by WIMP annihilation. Current results are puzzling and the hints of detection will be tested soon. At the end of the talk I'll briefly turn to dark energy and its effect on the fate of the Universe.

Gauge-field inflation and the origin of the matter-antimatter asymmetry
March 28, 2018 | ERC 401 | 3:30 PM | KICP Colloquium
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.

Science, Politicians, and the Public: What's the Story?
April 4, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Rush D Holt, AAAS

Video
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?

Preliminary Cosmology Results from the Dark Energy Survey Supernova Program
April 11, 2018 | ERC 161 | 3:30 PM | KICP Colloquium
Click on the image to enlarge
Rick Kessler, The University of Chicago

Video
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.

Pushing the Boundaries: Expanding Possibilities for Exoplanet Atmospheric Characterization
April 18, 2018 | ERC 161 | 3:30 PM | Host: Leslie Rogers | Astronomy Colloquium
Click on the image to enlarge
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.

Strong Lensing: Lenses and Sources
April 25, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
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.

Refreshments served at 4:30 PM, Hubble Lounge

The Multi-Messenger Picture of a Neutron Star Merger
May 2, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
Click on the image to enlarge
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.

Refreshments served at 4:30 PM, Hubble Lounge

The State of Small-Scale "Crises" In Dark Matter
May 9, 2018 | ERC 161 | 3:00 PM | KICP Colloquium
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.

Reception at 4:30 PM in the ERC 401.

The Remarkable Assembly History of Elliptical Galaxies
May 16, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
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.

Refreshments served at 4:30 PM, Hubble Lounge

The Simons Observatory
May 23, 2018 cancelled | ERC 161 | 3:30 PM | KICP Colloquium
Brian Keating, UC San Diego

CANCELLED

Reception at 4:30 PM in the ERC 401.

TBA
May 30, 2018 | ERC 401 | 3:30 PM | Astronomy Colloquium
Ken Sembach, STScI

Refreshments served at 4:30 PM, Hubble Lounge

TBA
June 6, 2018 | ERC 161 | 3:30 PM | Astronomy Colloquium
Kathryn Johnston, Columbia University

Refreshments served at 4:30 PM, Hubble Lounge