Astrophysics Colloquium

Colloquium Meetings are held in the Physics and Astronomy Building (PAB) in Room 1-434A from 3:30-4:30 pm every Wednesday of the Academic Year.

Coordinator: Smadar Naoz

Fall 2017 Schedule

Date Speaker Title 

Dong Lai

Circumbinary Accretion: From Supermassive Binary Black Holes to Circumbinary Planets

Circumbinary disks have been observed in a number of young stellar systems, and are the birth place for circumbinary planets found by the Kepler misssion. They are also expected to exist around supermassive black hole binaries as a consequence of accretion from the interstellar medium following galaxy mergers. I will discuss recent works on numerical modeling of circumbinary accretion, focusing short-term and long-term variabilities, and angular momentum transfer between the disk and the binary -- the result suggests that the long-standing notion of binary orbital decay driven by circumbinary disk may be problematic. Implications for planet formation/migration around stellar binaries will be noted. I will also discuss the dynamics and evolution of inclined/warped disks in binaries and connect with recent observations of protoplanetary disks and circumbinary planets.


Michael Boylan-Kolchin

The Faint Frontier of Galaxy Formation

The faintest stellar systems — dwarf galaxies and globular clusters in the nearby Universe and all galaxies in the reionization era — provide some of the most stringent tests of our theories of galaxy formation and dark matter. I will discuss how our understanding of these faint objects has evolved in the past 15 years, driven in large part by digital sky surveys and detailed spectroscopic observations, and provide an assessment of the current status of potential small-scale challenges to the prevailing LCDM cosmology. I will also describe deep connections between the nearby and distant faint frontiers. These links point to novel ways to test our models of galaxy formation, cosmology, and dark matter in the coming era of JWST, LSST, and 30m-class telescopes.


Louis Abramson

What does it mean to “study galaxy evolution”?

Huge amounts of data describe the appearance of the cosmic galaxy ensemble over at least the past 10 billion years; i.e., 75% of all time. Further, computer simulations produce reasonable facsimiles of many of these observations based on established ideas of hydrodynamics, gravity, and cosmology. Nevertheless, the answers to basic questions—Why do galaxies have the mass, size, and color that we observe?—elude us. In this talk, I will explore some of the fundamental issues that I think hamper progress towards an intellectually satisfying, consensus Theory of Galaxy Evolution. These will range from “semantics” regarding the definitions of commonly used phrases, to epistemological disconnections between data and models that may be unique to astronomy. To guide this exploration, I will draw on work by myself and others surrounding a few key observations related to galaxies’ sizes, star formation rates, and stellar masses, and my latest efforts to move some of these data closer to the model predictions they are (in principle) taken to test. I will close with my ideas for future work in this vein, and my (optimistic!) thoughts about the future of galaxy evolution as an area of basic research.


Blakesley Burkhart

New Diagnostics of MHD Turbulence in the Multiphase Interstellar Medium

Our current view of the interstellar medium (ISM) is as a multiphase environment where turbulence affects many key processes. These include star formation, cosmic ray acceleration, and the evolution of structure in the diffuse ISM. It is therefore essential to study and quantify interstellar turbulence using the strengths of numerical simulations in concert with observational studies. In this talk, I shall discuss progress in the development of new techniques for comparing observational data with numerical MHD simulations in the molecular medium, in neutral gas as traced by HI, and warm ionized gas as traced by synchrotron polarization. I will show how a confluence of simulations and novel multiwavelength measurements have taught us that: 1) The ISM in our Galaxy and nearby galaxies is supersonic in both the diffuse and molecular media, 2) Turbulence is primarily driven at scales larger than 100 parsecs, and 3) the magnetic field is a critical regulator of star formation. I will demonstrate how these measurements open up new avenues for studying star formation, cosmic ray acceleration and the formation of molecules in the ISM.


Ramesh Narayan




Keivan Stassun

The Royal Road, Redux: Eclipses and Transits in the Era of Gaia and TESS

In his 1946 inauguration of the lectureship that now bears his name, Henry Norris Russell described eclipses as a "royal road" that "repays its followers richly." I begin by summarizing results from a number of rare, but astrophysically important eclipsing binary stars that have paid richly in our understanding of the effects of magnetic activity on the physical structure of low-mass stars and brown dwarfs. Next, I describe how eclipsing binary stars serve as independent, empirical benchmarks for trigonometric parallaxes---with an accuracy of 200 micro-arcseconds or better that does not degrade with distance---and show an application of such a test to the first Gaia parallaxes (spoiler: there are some problems, but not too bad). I then describe an approach by which the Gaia parallaxes, together with observations of planetary transits of stars, permit the radii and masses of stars and planets to be measured with an accuracy of better than 5%, in an entirely empirical fashion. Already with the first Gaia parallaxes it is possible to assess the true masses of evolved planet-host stars (spoiler: they are mostly massive stars). I briefly summarize key results from the KELT transit survey and its implications for the science yield from the upcoming TESS mission specifically for massive stars, which are underrepresented in current planet surveys. Finally, returning to Henry Norris Russell's famous H-R diagram as an example, I conclude with some remarks on the role of data visualization in scientific discovery, and describe new efforts to quantify neuro-diverse visuo-cognitive capabilities in order to teach humans and machines to visualize data autistically.


Laura Chomiuk

Rethinking the Fundamentals of Classical Nova Explosions

Over the past few years, a revolution has been taking place in our understanding of classical novae, largely driven by the discovery of GeV gamma-rays emanating from these garden-variety explosions. These gamma-rays hint that shocks are energetically important---perhaps even dominant---in novae. I will present our burgeoning understanding of shocks in novae, from both multi-wavelength observational and theoretical perspectives. I will also illustrate how novae can be used as testbeds to understand other shock-powered explosions, like stellar mergers and super-luminous supernovae.



Thanksgiving Day Observance



Pieter van Dokkum




Jess Werk



Colloquium Archive:

Date Speaker Title 

Jennifer van Saders, Carnegie

Making Sense of Stellar Rotation Observed with Kepler: Gyrochronology, Magnetism, and a Sun in Transition

Stellar rotation carries a wealth of information about stellar populations. In particular, the technique of gyrochronology was developed to utilize the spin-down of stars as a function of time as an indicator of stellar age. Gyrochronology has the potential to yield precise ages for large samples of stars, providing unprecedented chronological information for studies of the Milky Way and extrasolar planets. However, the technique is in its adolescence: it has been tested and validated under limited scenarios, but its weaknesses and limitations have hitherto been largely unexplored. With time-domain data from the Kepler mission we can address these gaps: we now have access to datasets of rotation periods for tens of thousands of stars, as well as independent asteroseismic ages and rotation periods for a few hundred old (main sequence) stars. I will discuss my comparisons of theoretical rotation models to these Kepler data, which have yielded unexpected insights into the rotational and magnetic lives of stars (and the Sun!), as well as a better understanding of the power and peril of gyrochronology as a tool.


Aomawa Shields, UCLA

Ice, Light, and Company: Radiative and Gravitational Effects on the Habitability of Planets Orbiting Low-mass Stars Aomawa Shields

The recent discovery of numerous potentially habitable planets orbiting low-mass stars signals a major planetary population that may be the primary environment explored in the search for life beyond the Solar System. However, many factors and processes can affect planetary climate and habitability, including the unique interaction between the spectral energy distribution of the host star and the atmospheres and surfaces of orbiting planets. Additionally, as lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant effects on climate and habitability over long timescales. To identify habitable worlds beyond our Solar System, it is important to understand how both orbital, surface, and atmospheric properties affect the climate of exoplanets, and how these climatic effects might change for different stellar and planetary environments. I will share results from work performed using a hierarchy of models to simulate planets orbiting stars of different spectral types and with varied orbital architectures, and discuss the implications of these results for planetary climate and habitability.


Assaf Horesh, Hebrew University

Forensics of Stellar Death Through Radio-Wave Eyes

The dynamic radio sky is seen as a frontier area in astrophysics, ripe for discovery, as recent technological advancements enable the comprehensive study of cosmic explosions. By comparison to observations in other wavelengths, radio observations offer unique diagnostics, as they trace high-energy particles, magnetic fields - and reveal fast and relativistic outflows, which otherwise remain hidden. In the case of supernovae, the complex process of mass-loss, a key ingredient in the last stages of stellar evolution, can be illuminated by thoroughly mapping the circumstellar medium, around the progenitor. Radio observations can also help identify the physical process responsible for launching fast outflows and/or relativistic jets such as in a stellar disruption by a supermassive black hole. More importantly, whenever a new class of transients has emerged, radio observations played a key role in unveiling their nature. While the field of radio time-domain astronomy has seen a tremendous progress over the last decade, just now we are on the verge of a revolution as (a) next generation synoptic surveys searching for cosmic explosion are becoming available, (b) the radio astronomy field is experiencing a renaissance with new and improved facilities, and (c) the first detection of a gravitational wave opened a new window for discoveries.


Ben Shappee, Carnegie

The All-Sky Automated Survey for Supernovae

For the first time, the entire visible sky is being surveyed for the violent, variable, and transient events that shape our universe. To accomplish this, my collaborators and I built the All-Sky Automated Survey for Supernovae (ASAS-SN), which is a long-term project to monitor the whole sky, at a high cadence, using a global network of robotic telescopes. The primary goal of ASAS-SN is to find the closest and brightest supernovae (SNe) with an unbiased search: ASAS-SN now discovers about two-thirds of all bright (V<17 mag) supernovae. These nearby supernovae are critical in studying the physical nature of their progenitor systems because we can study them in unprecedented detail across the electromagnetic spectrum which cannot be done for their more distance counterparts. However, this systematic all-sky technique also allows ASAS-SN to discover many other interesting galactic and extragalactic transients. During this talk, I will give an overview of the ASAS-SN survey and highlight some of our more interesting discoveries. These discoveries include ASASSN-15lh, likely the most luminous supernovae ever discovered; ASASSN-14lp, one of the earliest observed Type Ia supernovae; ASAS-SN16ae, the largest (Delta V > 11 mag) and second-ever L-dwarf flare; and ASASSN-14ae, ASASSN-14li, and ASASSN-15oi, the three brightest tidal disruption events discovered in the optical. These discoveries, however, are just the beginning. In 2017 ASAS-SN will more than double in size, allowing us to survey the visible entire sky with better than a daily cadence while being more resistant to weather.


Dan Marrone, University of Arizona

The Cosmic Abundance of Molecular Gas: Intensity Mapping the Faint Universe

The cool, molecular phase of the interstellar medium is the fuel that enables the formation of new stars. In the early universe, large gas reservoirs dominated the baryonic mass of galaxies and enabled a cosmic star formation density that peaked at 10 times the current value. While the light from young stars has made it possible to trace the star formation itself, observing the molecular gas itself is much more difficult. This phase, typically traced by CO emission, has only been observed at high redshift in the most massive objects, while normal galaxies are nearly inaccessible to even the most sensitive radio telescopes. The technique of “intensity mapping,” which measures the aggregate molecular emission from the three-dimensional distribution of galaxies, provides a tool to detect the faint signal of the molecular ISM and chart its history across cosmic time. I will describe a staged program of intensity mapping that targets CO emission from the peak of cosmic star formation to the present. The first phase, the CO Power Spectrum Survey (COPSS), used archival and targeted observations with the CARMA interferometer to constrain the CO power spectrum at z~3 for the first time. I will review these measurements and their implications for the distribution of molecular gas in the universe. This work is now transitioning into new phases in which we use archival and new data from the most sensitive radio telescopes to further explore the growth of the ISM, and ultimately deploy a purpose-built instrument to Kitt Peak to survey the universe from z~0 into the epoch or reionization.


Ranga-Ram Chary, Caltech/IPAC-Planck

Unexpected Spectral Variations in the Cosmic Microwave Background: Constraining the Alternate Universe Hypothesis

The fine-tuning of initial conditions required to reproduce our present day Universe and the value of the vacuum energy density therein, suggests that our Universe may merely be a region within an eternally inflating super-region. Many other regions could exist beyond our observable Universe with each such region governed by a different set of physical constants than the ones we have measured for our Universe - this is the alternate Universe hypothesis. Some groups think that testing the existence of alternate Universes and thereby the theory of eternal inflation is an impossible goal. However, if chance collisions occur between these regions, they should leave signatures of anisotropy in the cosmic microwave background. I will present our analysis of the Planck data which has led to the detection of at least one statistically significant spectral anomaly at the location of a high-latitude CMB cold spot. The intensity of this anomaly, if foregrounds are ruled out, would favor a collision with an alternate Universe, inducing compensated isocurvature fluctuations with a much different baryon to photon ratio than in our own Universe. This would suggest an anthropic explanation for the value of the cosmological constant and provide an astrophysical way to test string theory. Future, observational tests of this hypothesis will also be discussed.


Rychard Bouwens, Leiden Observatory

Young Galaxies Forming in the High-Redshift Universe

Over the last few years, enormous progress has been made in studying galaxies in the first two billion years thanks to the incredible capabilities of the Hubble and Spitzer Space Telescopes. Already, more than 1500 probable galaxies are known at redshifts above z~6, and now the current frontier is at z~9-10, with 50 plausible galaxy identifications to date, and a spectroscopic redshift measurement to z=11.1. Noteworthy advances are also being made in characterizing the physical properties of these distant galaxies, with probes of the nebular emission lines and specific star formation rates to z~8.5 and new constraints on dust-enshrouded star formation at z>~2 from ALMA. One area where there has been particularly exciting activity is in the study of ultra-faint galaxies in the early universe with the Hubble Frontier Fields (HFF) program, combining the power of long exposures with Hubble and Spitzer with gravitational lensing by massive galaxy clusters. In this colloquium, I survey these and other highlights of current research on high redshift galaxies, while looking forward to future work with JWST.


Phil Marshall, Stanford/KIPAC

Time Delay Cosmography with LSST

Strong gravitational lenses have become an important astronomical tool: they allow us to make accurate measurements of galaxy masses, they provide a magnified view of the distant universe, and they allow us to constrain cosmological parameters. In particular, the time delays in multiply-imaged quasar systems enable measurements of distance in the Universe each with around 5% precision. I will review recent measurements of time delay distance in galaxy-scale lens systems in the context of a longer term vision of how we can realize the potential of this cosmological probe, by increasing the size of our lens sample, and continuing to improve the accuracy of its analysis. More broadly, I'll use the example of time delay cosmography to introduce the LSST, its Dark Energy Science Collaboration, and what it will take to do accurate cosmology with its Big Data set.


Guinevere Kauffmann, MPA

Observations and modelling of gas in and around galaxies

This talk will focus on gas galaxies in the low redshift universe. I will review recent advances in quantifying scaling relations for atomic hydrogen in galaxies using radio telescopes, as well as the diffuse gas around galaxies using Hubble Space Telescope UV spectroscopy of quasars whose sight-lines pass through the halos of galaxies similar to our own Milky Way. I will show how such observations constrain galaxy formation models, in particular the physical processes that regulate the heating and cooling of gas as a function of cosmic epoch.


Zach Berta-Thompson, CU Boulder

Small Planets Transiting Nearby Small Stars

When you stand on a mountain admiring a colorful sunset, some light from the Sun passes over your shoulder and continues on through our atmosphere and out into space. As that light journeys out to distant stars, it carries with it the spectral fingerprint of our atmosphere’s molecules and aerosols. Astronomers have found thousands of small planets transiting other stars, many of them small enough to be rocky. In principle, we could observe the transmission spectrum of these planets’ atmospheres and use these observations to illuminate how these often-weird planetary atmospheres work. In practice, such observations are possible for small planets only when then transit very nearby, very small stars. I will present our efforts with the MEarth Project to find these systems, including our recent discovery of the transiting, terrestrial, potentially habitable planet LHS 1140b. I will also present our efforts to observe exoplanet atmospheres with multiobject spectroscopy from the ground, and I will discuss the landscape for small planet characterization in the TESS and JWST era.

Date Speaker Title (mouseover for abstract)

Dan Weisz, UC Berkeley

The Lowest-Mass Galaxies In the Early Universe: Insights from the Local Group

The Local Group is home to ~100 galaxies less massive than the Small Magellanic Cloud (10^8 Msun).  Such low-mass galaxies have become increasingly relevant to a broad range of astrophysics from cosmic reionization to deciphering the nature of dark matter.  Yet, they are simply too faint to be directly detected at any appreciable redshift, compromising our ability to place them into a cosmological context. In this talk, I will describe how observations of resolved stellar populations in Local Group galaxies enable the measurement of detailed star formation histories, which provide the only avenue for tracing the evolution of low-mass galaxies across cosmic time. I will review our current knowledge of low-mass galaxy evolution over 6 decades in stellar mass, with a particular emphasis on the very early Universe.  I will illustrate how local and high-redshift galaxy observations can be used in tandem to improve our understanding of cosmic reionization, and will conclude by discussing prospects for increased synergy between near-field and far-field galaxy studies in the JWST era.


Andy Skemer, UCSC

Characterizing the Coldest Exoplanets

Temperature, rather than mass, is the dominant factor in determining the appearance of gas-giant planets, and the diversity and complexity of worlds both increase at cold temperatures.  The coldest known exoplanets are still much hotter than the gas giant planets in our own Solar System.  Pushing to colder temperatures requires imaging in the thermal infrared (3-5 microns) where self-luminoous gas-giants peak in brightness.  I will present observational studies characterizing the atmospheres of the coldest exoplanets and brown dwarfs, down to a temperature of 250K.  Additionally, I will describe a new instrument that can obtain thermal infrared spectroscopy of directly imaged planets for the first time.

1-25-17 Massimo Stiavelli, STScI

Space Telescope Science Institute, USA

I will review the capabilities of the James Webb Space Telescope to study the era of the first stars, particularly focussing on the study of lensed or unlensed primordial star clusters or dwarf galaxies. I will discuss possible avenues of discovery of pair-instability supernovae using JWST or other telescopes, and how JWST could follow them up. Finally, I will provide a brief status on the mission and on the upcoming opportunities to learn more about JWST and propose for time.


2-1-17 Andrey Kravtsov, U Chicago 

Towards understanding the inefficiency of star formation in galaxies

Understanding how galaxies form is one of the main unsolved problems in astrophysics. One of the long-standing puzzles is the global inefficiency with which galaxies convert baryonic matter available to them into stars. This inefficiency is manifested in 1) the fact that ratio of baryon mass observed within galaxies to the total inferred mass of their host halos is much smaller than the universal baryon fraction and 2) the fact that galaxies convert their observed gas into stars on ~1-2 Gyr time scale (aka depletion time), which is much longer than any dynamical time scale within galaxies. I will review recent progress in galaxy formation simulations due to improvements in treatment of stellar feedback and star formation, which sheds light into the 1st aspect of inefficiency. I will highlight the key role that modelling of star formation and stellar feedback play in setting the basic properties of galaxies, such as stellar mass (and global baryon mass fraction), size, and morphology using specific examples of recent galaxy formation simulations. I will present a new model, in which local star formation efficiency is modelled "on the fly" using a turbulence-based subgrid model based on results of high-resolution simulations of molecular clouds. The model predicts a wide variation of star formation efficiency per free fall time at odds with the usual assumption of constant efficiency. At the same time, our model predicts distribution of star formation rates in broad agreement with observations of both local and resolved extragalactic GMCs. I will show that with realistic implementation of stellar feedback this modelling can reproduce the basic properties of star formation and the Kennicutt-Schmidt relation in galaxies, such as the Milky Way. Finally, using insights from such simulations I will present a simple model explaining why star formation in galaxies is inefficient and depletion times are long.

2-8-17 Fred Rasio, CIERA

Dense Star Clusters as LIGO Source Factories

Theoretical predictions for compact binary mergers from field populations of binary stars are extremely sensitive to the assumptions of stellar evolution, leading, for example, to predicted merger rates for binary black holes that span several orders of magnitude. But in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. In this talk I will present an overview of recent theoretical work on the dynamical formation of black hole binaries based on realistic N-body simulations of globular clusters. By calibrating theoretical models against observed Milky Way and extragalactic globular clusters, we find that the mergers of dynamically formed binaries could eventually be detected by Advanced LIGO at a rate of ~ 100 per year, potentially dominating the overall detection rate of gravitational wave sources. Dynamical processes in globular clusters can also form very naturally the more massive black hole binaries like the one that produced GW150914, the first merger signal detected by LIGO.

2-15-17 James Guillochon, CfA

 The Impact of the Debris from Stellar Tidal Disruptions on their Environment

Abstract: When a star is destroyed by tides from a supermassive black hole, the star is stretched into a long, extraordinarily thin debris stream that extends from the star's original periapse (about an AU from the black hole) to distances of tens of parsecs. As the stream extends, it simultaneously cools, clumps, magnetizes, and slams into the ambient medium, delivering a supernova's worth of kinetic energy into the surrounding gas. In my talk, I will describe the predicted observable phenomena arising from this debris, and the impact it can have in the centers of galaxies.
2-22-17 Jennifer Lotz, STScI

 Galaxy Assembly over Cosmic Time

Abstract: Deep HST observations have revealed galaxies fainter than ever seen before, at look-back times when the universe was less than a billion years old. These first dwarf galaxies grow throughout cosmic time via the accretion of gas and dark matter, and via mergers with other galaxies. The detailed structures of galaxies provide direct insight into their most recent assembly events. From large high-resolution imaging surveys, we now have a broad-brush picture of how galaxy shapes and sizes have evolved over the past 10 billion years. But the role of galaxy mergers in galaxy evolution is poorly understood, particularly at early times. More subtle morphological tracers are needed to track the complex processes responsible for the transformation of galaxies. I use new machine learning classifications of galaxy morphology at 0 < z < 3 to identify galaxy mergers and galaxies transitioning to today's Hubble types. Numerical simulations are used to inform the interpretation of these systems. I track the evolution of galaxies as a function these new measures, and discuss the role of mergers in the size growth of galaxies. Finally, I discuss the prospects for studying galaxy assembly in the coming decade.

3-1-17 Emily Rauscher, U. Michigan

The Diversity and Complexity of Exoplanet Atmospheres

We are now in the era of exoplanet characterization.  Over a decade ago the first exoplanet atmosphere was detected and since then we have been gathering compositional and temperature information for the brightest targets, primarily "hot Jupiters".  Recent technical advances are enabling measurements that contain more complex information about exoplanet physical properties; however, that additional complexity also makes interpretation of the data more difficult.  I will discuss the extra boons and challenges that come with these newer measurements, and present my own work on using three-dimensional atmospheric circulation models to guide and interpret observations.  In particular, I will show how we can combine different types of measurements in order to robustly measure, or at least constrain, exoplanet physical properties such as: wind speeds, magnetic field strengths, rotation rates, or obliquities.  As exoplanet missions identify more bright targets for atmospheric characterization, we will be able to apply these techniques to planets beyond hot Jupiters, in our inevitable march toward identifying potentially habitable worlds


 Keren Sharon, U. Michigan

 The Universe, Magnified: The Power of Gravitational Lensing

Abstract: When did the Universe form its first galaxies? What do galaxies look like at the epoch when the Universe formed most of its stars? Some of the answers to those questions (and others) await a new generation of large ground and space based telescopes. In the meanwhile, strong gravitational lensing has become a useful tool to boost the power of present day telescopes, enabling detailed studies of galaxies that are otherwise either too dim or have too small of an angular size on the sky.

3-15-17 Maryam Modjaz NYU

 Stellar Forensics with the Most Powerful Explosions in the Universe

Abstract: Supernovae and Gamma-ray Bursts are exploding stars and constitute the most powerful explosions in the universe. Since they are visible over large cosmological distances, release elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics, including cosmology. However, for many years the fundamental question of which stellar systems give rise to which kinds of explosions has remained outstanding. I will discuss the exciting recent progress that we have made on this question in key areas by publishing and thoroughly analyzing the largest data sets in the world. I will conclude with an outlook on how the most promising venues of research - using the existing and upcoming innovative large time-domain surveys, such as the Large Synoptic Survey Telescope - will shed new light on the diverse deaths of stars.


Avery Broderick (Waterloo/Perimeter Institute)

The Current and Future View from the Edge


Tom Greene (NASA Ames)

Characterizing Exoplanets with JWST

10-12-2016 Ciska Kemper (ASIAA)

The production of dust by evolved stars in the Magellanic Clouds and other galaxies

10-19-2016 George Becker (UCR)

The Intergalactic Medium Near Reionization

10-26-2016 Quinn Konopacky (UCSD)

Constraining Planet Formation with Directly Imaged Exoplanets

11-02-2016 Ryan Foley (UCSC)

Continuing the Legacy of Supernova Cosmology

11-09-2016 Rachel Somerville (Rutgers)

The Connection between Quenching and Galaxy Structure

11-16-2016 Chuck Steidel (Caltech)

Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies

11-23-2016 NO COLLOQUIUM Thanksgiving Day Observance
11-30-2016 Sarah Ballard (MIT)

The Grand Planetary Ensemble



Date Speaker Title (mouseover for abstract)

Bryan Gaensler                           (Dunlap Institute)

Radio Polarimetry and Cosmic Magnetism


Joel Primack (UCSC)

New Insights on Galaxy Formation from Observations and Simulations


Kevin Schawinski (ETH)

The galaxy-black hole connection

04-20-2016 Pascal Oesch (Yale)

Galaxy Build-up at Cosmic Dawn: Hubble's Lasting Legacy

04-27-2016 Laura Lopez (OSU)

Observational Assessment of Stellar Feedback in Star-Forming Regions


Nitya Kallivayalil                          (U. of Virginia)

Probing the Dark Halo of the Milky Way

05-11-2016 Scott Gaudi (OSU)

Gravitational Microlensing Surveys for Exoplanets: A Watershed

05-18-2016 Jay Strader (MSU)

Black Holes in Globular Clusters


Rennan Barkana (TAU)

Novel Measurements of Starlight from Cosmic Dawn to the Present

06-01-2016 Daryl Haggard (McGill)

Interpreting Sgr A*'s Most Luminous X-ray Flares



Date Speaker Title (mouseover for abstract)

 No Colloquium

No Colloquium (AAS)


 Dan Stark (U of Arizona)

Galaxies in the Reionization Era


 Alyssa Goodman              (Harvard)

The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs

01-27-2016  Mark Swain (JPL)

Exoplanet Transit Spectroscopy Surveys:Present and Future

02-03-2016  Avi Shporer (JPL)

Science with orbital phase curves in the space age

02-10-2016  Alice Shapley (UCLA)

The MOSFIRE Deep Evolution Field (MOSDEF) Survey: Insights into the Evolving Physical                                                    Conditions in Star-forming Regions at High Redshift

02-17-2016  No Colloquium


02-24-2016  Sarah Tuttle (UT Austin)

Alt-Instrumentation – From Ground to Space


 David Spergel (Princeton)

From '~' to precision science: Cosmology from 1995 to 2025

03-09-2016  Kevin Bundy (IPMU)

Galaxy Death and the Role of 'Red Geysers'

Date Speaker Title (mouseover for abstract)

 Paul Schechter (MIT)

The measurement of stellar masses in <z> = 0.5 galaxies using the micro-lensing of quasars


 Alycia Weinberger (Carnegie DTM)

Tracing the Formation of Planetary Systems



Veteran's Day

 Courtney Dressing (Harvard/CalTech)

The Frequency and Composition of Small Exoplanets



Thanksgiving Day Observance

 Karin Oberg (Harvard)

The Chemistry of Planet Formation

Date Speaker Title (mouseover for abstract)
04-01-2015  Ji Wang (Yale)

Planet Formation Under Different Environments

04-08-2015  Gwen Rudie (Carnegie/Princeton)

Observing the Baryon Cycle: The Circumgalactic and Interstellar Medium of Galaxies at 2<z<3

04-15-2015  Ann-Marie Madigan (UC Berkeley)

From the Solar System to the Galactic center: unstable disks and infalling clouds

04-22-2015  Nir Shaviv (IAS Princeton/ Hebrew University of Jerusalem)

Cosmic rays and the structure of the Milky Way’s Disk: From the Pamela Anomaly to Paleoclimatology

04-29-2015  Dimitri Mawet (Caltech)

The future of exoplanet imaging and spectroscopy at Keck

05-06-2015  Eric Ford (Penn State)

Characterizing the Distribution of Planetary Architectures with Kepler: The Formation of Systems with Tightly-packed Inner Planets (STIPs)

05-13-2015  Dimitrios Psaltis (U. of Arizona)

Testing General Relativity with the Event Horizon Telescope

05-20-2015  Daniel Stern (JPL)

Surprising New Insights into Quasars from the WISE Satellite

05-27-2015  Drew Newman (Carnegie/Princeton)

Observing the Assembly of Massive Galaxies

06-03-2015  Fabienne Bastien (Penn State)

Convection in Cool Stars, as Revealed through Stellar Brightness Variations