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Past Events

Event Date Summary
Astronomy Colloquium: Keren Sharon Tue. April 24th, 2018
2:30 pm-3:30 pm

The Universe, Magnified: The Power of Gravitational Lensing

Keren Sharon (Michigan)

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. 
Astronomy Colloquium: Dimitar Sasselov Thu. April 12th, 2018
4:00 pm-5:00 pm

Ocean Worlds: from Familiar to Exotic and Extreme Planets

Dimitar Sasselov (Harvard)

Water is a common molecule in the the galaxy and an abundant bulk component of planets – like Neptune, far from their stars. Liquid water – a precious solvent,  might be significantly more rare. Exoplanet exploration is both motivated by the search for surface liquid water and is helping us understand the wide diversity of ocean worlds. Such understanding is necessary if we are to succeed in the search for planetary conditions that could lead to the emergence of life.
(Note special day and time)
Astronomy Colloquium: Brett Denevi Thu. March 1st, 2018
2:30 pm-3:30 pm

Our Goals for Lunar Science and Exploration

Brett Denevi (JHU/APL)

NASA has recently announced plans to refocus its attention on the Moon as a cornerstone for Solar System science and exploration. However, similar announcements were made in the not-so-distant past, only to be cancelled before they could come to fruition. What have we learned along the way? And what can we learn from new orbital and landed missions to the Moon? I will present recent highlights in lunar science, the highest priority lunar science goals as determined by the National Research Council, and some of the ways we will seek to answer those questions.

Astronomy Colloquium: Caitlin Casey Tue. February 13th, 2018
2:30 pm-3:30 pm

The Universe’s Most Extreme Star-Forming Galaxies in the Most Extreme Environments

Caitlin Casey (Texas)

Dusty star-forming galaxies host the most intense stellar nurseries in the Universe. Their unusual characteristics (star formation rates of 200-2000 Msun/yr, compared to the Milky Way’s 1 Msun/yr) pose a unique challenge for cosmological simulations of how galaxies form and evolve, particularly in the first few billion years after the Big Bang. Although rare today, these unusual galaxies were factors of 1000 times more prevalent 10 billion years ago, contributing significantly to the buildup of the Universe’s stars during catastrophic galaxy-galaxy collisions that ignited shortlived but extremely powerful bursts of star formation.

Astronomy Colloquium: Cameron McBride Tue. January 30th, 2018
2:30 pm-3:30 pm

Data Science: The what, why, and how of my transition from Science to Tech

Cameron McBride (Rubicon Project)

Data science continues to explode as a field as the industrial need for scientific rigor grows. It can be referred to by many names: machine learning, artificial intelligence, statistics, science, or sometimes even software engineering. I trained to be an academic scientist, and did research in extragalactic astronomy and cosmology across four major research institutions and as part of an international collaboration. Over the past three years, I have worked for two startups and a larger corporation solving challenging problems across two fields.

Astronomy Colloquium: Jillian Scudder Tue. January 16th, 2018
2:30 pm-3:30 pm

Title: The hunt for cosmic monsters: understanding galaxies in the confused FIR sky

Jillian Scudder (Oberlin)

Observing galaxies in the Far-Infrared (FIR) gives us a unique window into the star formation rates of very high redshift, dusty galaxies. These galaxies are generally thought to be forming stars at a prodigious rate, heating their dust within their host galaxy, which then radiates in the FIR. However, observing this luminous dust is difficult, even with a space-based telescope such as the Herschel Space Observatory, as the resolution of the images returned is quite poor. It is often assumed that a bright source in the FIR belongs to a single,

Astronomy Colloquium: Mark Vogelsberger Thu. December 14th, 2017
3:00 pm-4:00 pm

Simulating Galaxy Formation: IllustrisTNG and beyond

Mark Vogelsberger (MIT)

In my talk I will describe recent efforts to model the large-scale distribution of galaxies with cosmological hydrodynamics simulations. I will focus on the Illustris simulation, and our new simulation campaign, the IllustrisTNG project. After demonstrating the success of these simulations in terms of reproducing an enormous amount of observational data, I will also talk about directions for further improvements over the next couple of years.

Astronomy Colloquium: Ben Monreal Tue. December 5th, 2017
3:00 pm-4:00 pm

hWAET: a ground-based telescope for exoplanet direct imaging

Ben Monreal (CWRU Physics)

In the literature on telescope conceptual design, there is a divide which at first glance seems unusual: space telescope design is a free-for-all while ground based concepts are very conservative. As an instrument-builder, although most of my work is on neutrinos and dark matter I am also wading into the understudied edges of ground-based telescope design. In this talk, I will introduce WAET, a new (but still fairly conservative) construction concept for large ground-based optical/IR telescopes. WAET is intended to use conventional components and prescriptions to get to huge apertures at extremely low cost.

Astronomy Colloquium: Phil Hopkins Fri. November 17th, 2017
2:00 pm-3:00 pm

Stars Re-Shaping Galaxies

Phil Hopkins (Caltech)

The most fundamental unsolved problems in galaxy formation revolve around “feedback” from massive stars and black holes. I’ll present new results from the FIRE simulations which combine new numerical methods and physics in an attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to ‘self-regulated’ galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation — the stellar mass function —

Astronomy Colloquium: Jason Wright Tue. November 7th, 2017
3:00 pm-4:00 pm

The Puzzle of Boyajian’s Star

Jason Wright (PSU)

I have been at the center of efforts to understand KIC 8462852, a strange star found during the Kepler mission. It exhibits deep, irregular “dips” or dimming events lasting days, up to 22% in depth, and appears to be dimming secularly on decadal timescales. As ever-more-contrived natural explanations are proposed and explored by my team and others, we continue to put together monitoring and target-of-opportunity programs to catch it “in the act” of dipping and determine the nature of the dips. I will discuss the families of possible solutions for this star,

Astronomy Colloquium: David Silva Fri. October 13th, 2017
11:00 am-12:00 am

NOAO Today and Tomorrow

David Silva (Director, NOAO)

The National Optical Astronomy Observatory (NOAO) is the U.S. national center for ground-based optical-infrared (OIR) astronomy. It is a Federally Funded Research and Development Center (FFRDC) sponsored by the National Science Foundation (NSF) and managed by the Association of Universities for Research in Astronomy (AURA). The NOAO mission is to enable discovery for the research community-at-large through open access to world-class facilities, capabilities, services, and data products. At NSF request, AURA is developing a plan to create the National Center for OIR Astronomy (NCOA) by restructuring the Gemini Observatory,

Astronomy Colloquium: Annika Peter Mon. September 25th, 2017
1:30 pm-2:30 pm

Twinkle, twinkle, little galaxy

Annika Peter (OSU)

The littlest galaxies have the potential to tell us the most about the nature of dark matter and about star formation in extreme environments. In this talk, I describe what they are telling us already, what the open questions are, and my approach to answering them. I will highlight new opportunities with the next generation of astronomical surveys.

Astronomy Colloquium: Amanda Kepley Tue. September 12th, 2017
3:00 pm-4:00 pm

Opening New Frontiers in the Study of Star Formation with the Next Generation of Radio Telescopes

Amanda Kepley (NRAO)

Much of what we know about the molecular gas that fuels star formation comes from observations in the Milky Way and other similar nearby galaxies. This sample only probes a relatively narrow range of galaxy properties and thus does not provide an effective test of how galaxy properties like mass, metallicity, and star formation rate affect star formation. With the advent of new instruments like Atacama Large Millimeter/submillimeter Array (ALMA), the Green Bank Telescope (GBT),
Astronomy Colloquium: Daniela Calzetti Thu. April 13th, 2017
2:30 pm-3:30 pm

The Scales of Star Formation – Insights from the UV

Daniela Calzetti (UMass)

Over two decades of observations from the Ultraviolet to the Infrared with a host of space missions, including the HST, Spitzer, Herschel, GALEX, etc. have enabled us to recover the census of both the intensity and the distribution of star formation within galaxies. This, in turn, is informing us on the physics underlying the links between star formation, feedback, and the natal gas from which stars form. I will present a few results of a recent HST treasury program that is building upon previous findings to shed light on the scales of star formation and their interlinks within galaxies.

Astronomy Colloquium: Jay Strader Wed. March 22nd, 2017
3:00 pm-4:00 pm

Black Holes in Globular Clusters

Jay Strader (Michigan State University)

Hundreds of stellar-mass black holes form in the early lifetime of a typical globular star cluster. But, unlike the case for neutron stars, no bright X-ray binaries containing black holes have been observed in globular clusters, which led to theoretical predictions that most or all of the black holes should be efficiently ejected through dynamical interactions. I will highlight results from an ongoing survey using deep radio continuum and X-ray data to search for accreting black holes in Milky Way globular clusters, presenting evidence that black holes may indeed be common in globular clusters.

Astronomy Colloquium: Chris Impey Thu. March 9th, 2017
2:30 pm-3:30 pm

Science Literacy in the MOOC Era

Chris Impey (Arizona)

In a world shaped by science and technology, the persistently low level of science literacy of the general
public is a cause for concern. This talk will look at the science knowledge and beliefs of undergraduates,
using an instrument tethered in the biennial surveys conducted by the NSF for the National Science Board.
Even after taking several science courses, students have only a vague idea of how science works and their
habits of mind are influenced by pseudoscience and easy access online information of dubious quality.

Astronomy Colloquium: Ian Roederer Wed. March 1st, 2017
3:00 pm-4:00 pm

Heavy Metals from the First Stars to Today

Ian Roederer (UMichigan)

NASA’s Cosmic Origins program aims to address the question, “How did we get here?”  My work addresses this question through three broad themes: the nature of the first stars, the formation and evolution of the Milky Way and Local Group, and the origin of the elements.  I study dwarf galaxies, globular clusters, and stars in the halo using optical and ultraviolet high-resolution spectroscopic data from various telescopes on the ground and the Hubble Space Telescope.  I will present observations of heavy elements that change our understanding of when and how they were first produced in the early Universe,

Astronomy Colloquium: Nelson Padilla Tue. February 21st, 2017
2:00 pm-3:00 pm

Angular momentum in galaxy formation simulations

Nelson Padilla (U Catolica de Chile)

In this talk I will present studies on the evolution of the angular momentum of galaxies in the EAGLE simulation where we try and identify the mechanisms that contribute to the growth of their angular momentum, including smooth mass accretion, mergers, and mergers with different degrees of alignment with the galaxy’s angular momentum.  We hope to be able to use these results to improve the way in which angular momentum is followed in more simplified models of galaxy formation including SAMs and HODs.

Astronomy Colloquium: Steinn Sigurdsson Wed. February 15th, 2017
3:00 pm-4:00 pm

How black holes get their kicks: dynamical evolution and coalescence

Steinn Sigurdsson (Penn State U)

Recent observations have increased interest in the possibilities of a significant population of black hole binaries in the local universe. Natal kicks may play a crucial role in the merger rate of stellar mass black holes. Dynamical evolution can lead to an enhanced interaction rate for compact binaries in dense stellar systems and a distinct and richer population of compact binaries. I discuss some of the issues related to black hole binary formation and coalescence, and the issue of retention in globular clusters.

Astronomy Colloquium: Laura Lopez Wed. January 25th, 2017
3:00 pm-4:00 pm

Observational Assessment of Stellar Feedback in Nearby Galaxies

Laura Lopez (Ohio State U)

Massive stars have a profound astrophysical influence throughout their tumultuous lives and deaths. Stellar feedback – the injection of energy and momentum by stars to the interstellar medium (ISM) – occurs through a variety of mechanisms: radiation, photoionization heating, winds, jets/outflows, supernovae, and cosmic-ray acceleration. Despite its importance, stellar feedback is cited as one of the biggest uncertainties in astrophysics today,

Astronomy Colloquium: Michael Skrutskie Fri. December 9th, 2016
11:00 am-12:00 pm

Diffraction-limited Mid-Infrared Imaging with the 23-meter Large Binocular Telescope

Michael Skrutskie (Virginia)

While the world awaits the construction of the Giant Magellan Telescope, Thirty Meter Telescope, and the European Extremely Large Telescope, the Large Binocular Telescope (LBT) at Mt. Graham, Arizona represents the first operating version of an “Extremely Large Telescope”.  The LBT consists of two 8.4-meter primary mirrors on a single alt-azimuth mount separated, center to center, by 14.4-meters creating an aperture that is nearly 23 meters in extent in one dimension.   The University of Arizona’s Large Binocular Telescope Interferometer (LBTI) coherently combines the light from the two primary mirrors enabling diffraction-limited imaging at a resolution set (on one axis) by the full extent of the 23-meter aperture. 

Astronomy Colloquium: Monica Valluri Wed. November 30th, 2016
3:00 pm-4:00 pm

Using the Stellar Halo to Probe the Assembly of the Milky Way

Monica Valluri (U Michigan)

Over the next decade there will be an explosion of high quality kinematical data on hundreds of millions of stars in the Milky Way’s stellar halo. We are using cosmological hydrodynamical simulations to explore what we can learn about the detailed assembly history of the Milky Way from these data. We have analyzed orbits of halo stars and correlations between orbital properties and intrinsic stellar properties such as stellar ages and metallicities. I will discuss what halo orbits can tell us about halo assembly.
Astronomy Colloquium: Kelly Holley-Bockelmann Thu. November 10th, 2016
2:30 pm-3:30 pm

Building Supermassive Black Hole Binaries

Kelly Holley-Bockelmann (Vanderbilt)

Astronomers now know that supermassive black holes reside in nearly every galaxy. Though these black holes are an observational certainty, nearly every aspect of their evolution — from their birth, to their fuel source, to their basic dynamics — is a matter of lively debate. In principle, gas-rich major galaxy mergers are key to generate the central stockpile of fuel needed for a low mass central black hole ‘seed’ to grow quickly and efficiently into a supermassive one. When the black holes in each galaxy meet,
Astronomy Colloquium: Ed Moran Wed. October 26th, 2016
3:00 pm-4:00 pm

AGN unification: the hidden truth

Ed Moran (Wesleyan U)

Seyfert galaxies have been traditionally classified into two groups based on the presence (type 1) or absence (type 2) of broad permitted emission lines in their optical spectra.  The discovery of polarized broad lines in a number of narrow-line Seyferts has indicated that such objects are in fact normal Seyfert 1 nuclei whose innermost regions are obscured from our direct view by a dense, torus-like structure.  By establishing a link between the two main classes of Seyfert galaxies, spectropolarimetry has led to significant progress in our understanding of the physics of active galactic nuclei (AGNs). 

Astronomy Colloquium: Doug Hamilton Fri. October 14th, 2016
11:00 am-12:00 pm

The Origin of Titan and Hyperion

Doug Hamilton (Maryland)

Titan is arguably the Solar System’s most unusual satellite. It is fifty times more massive than Saturn’s other moons and is the only satellite with a substantial atmosphere. Titan shares a unique resonance with nearby Hyperion, but otherwise sits in a particularly large gap between Rhea and Iapetus. Titan has the largest eccentricity of all Saturn’s regular satellites and has a reasonably large orbital tilt; its distant neighbor Iapetus has an even more impressive eight degree free inclination. Hyperion itself is a mystery, with its unusual orbit,

Astronomy Colloquium: Bill Janesh Wed. September 28th, 2016
3:00 pm-4:00 pm

Needles in a Haystack: Searching for Optical Counterparts to Ultra-compact High Velocity HI Clouds

Bill Janesh (Indiana University)

Low mass galaxies, and particularly those with recent or active star formation, are excellent laboratories to answer questions about galaxy formation and evolution. Due to their faint nature, however, they are difficult to detect. Ultra-compact High Velocity HI Clouds present an opportunity for a targeted search for resolved stellar populations in reservoirs of cold gas in the Local Volume. The recently discovered low-mass star-forming galaxy Leo P is an example of one such object.  We have begun a campaign to obtain deep imaging of a sample of ~50 UCHVCs selected from Arecibo’s ALFALFA HI survey with the aim of detecting or placing constraints on their possible optical counterparts.

Astronomy Colloquium: James Bullock Wed. April 13th, 2016
11:00 am-12:00 pm

Cosmology and the Local Group

James Bullock (UCalifornia, Irvine)

The Local Group and the tiny galaxies that surround the Milky Way provide unique and detailed data sets for testing ideas in cosmology and galaxy formation. In this talk I will discuss how numerical simulations coupled with local “near-field” observations are informing our understanding of dark matter, the formation of the first galaxies, and the physical processes that act at the threshold of galaxy formation.

Astronomy Colloquium: Hongsheng Zhao Mon. April 11th, 2016
11:00 am-12:00 pm

New Physics Beyond Galaxies

Hongsheng Zhao (University of St Andrews)

I will show how current data on galaxies and clusters could be used to constrain the new physics of dark matter and relativity.  I will propose a new theoretical approach to integrate MOND and Dark Matter.

Astronomy Colloquium: Elena D’Onghia Wed. March 30th, 2016
11:00 am-12:00 pm

The Structure and Dynamics of the Milky Way Stellar Disk

Elena D’Onghia (U Wisconsin)

Ongoing surveys are revolutionizing our understanding of Galaxy dynamics. At the same time, advances in computational cosmology have led to improved predictions for the properties of galaxies in the LCDM theory. This simultaneous progress has transformed the field of the dynamics of the Milky Way and its dwarf galaxies into a powerful testing ground for both cosmological and galaxy formation theories.  One important result of the last decades is that cosmological simulations of the Milky Way overpredict by a large factor the number of dwarf satellite galaxies orbiting our Galaxy.

Astronomy Colloquium: Kevin Stevenson Wed. March 16th, 2016
11:00 am-12:00 pm

Today’s Exo-Weather Forecast: Hot and Humid with a Chance of Clouds

Kevin Stevenson (Chicago)

Planet-finding surveys have revealed thousands of confirmed exoplanets and candidates awaiting verification.  Many of these objects were discovered indirectly using the transit technique, which is a powerful tool that has transformed our understanding of planetary system architecture.  Furthermore, this technique has provided extraordinary insights into some of these planets’ atmospheric compositions and thermal structures, thus revealing unexpected discoveries and altering our perspective of these worlds.  One of the most outstanding challenges in exoplanet characterization is understanding the prevalence of obscuring clouds and hazes in their atmospheres.

Astronomy Colloquium: Kathryn Johnston Thu. March 3rd, 2016
3:00 pm-4:00 pm

Dark Matter and Stellar Halos around Galaxies:  Formation, Histories and Structure

Kathryn Johnston, Columbia University

The existence of spectacular low-surface-brightness features – remnants of past mergers – surrounding many galaxies has been known about for many decades.  A major accomplishment for more recent, large scale stellar surveys of the Milky Way has been the discovery of a multitude of debris from dead and dying small satellites encircling our own Galaxy.  While these structures contain less than 1% of the light in the Universe and an even smaller fraction of the total mass their properties can be used to address fundamental topics,

Joint Phys/Astro Colloquium: John Monnier (Cancelled) Thu. February 25th, 2016
4:15 pm-5:15 pm

Cancelled due to inclement weather.

Astronomy Colloquium: Adam Leroy Wed. February 17th, 2016
11:00 am-12:00 pm

Star Formation-Driven Molecular Superwinds as Understood From the Two Nearest Starburst Galaxies (and a Small Survey)

Dr. Adam Leroy, Ohio State University

I will use the two nearest starburst galaxies: M82 and NGC 253 as examples to discuss the origin and fate of galaxy-scale molecular outflows driven by star formation. Outflows of interstellar gas driven by stellar feedback should be a key element in the interaction between galaxy disks and the huge reservoirs of gas and dust in the circumgalactic medium. They should carry metals and dust out of galaxy disks and may deplete future fuel for star formation.

Astronomy Colloquium: Tony Sohn Wed. February 3rd, 2016
11:00 am-12:00 pm

Dynamics of Local Group Galaxies via HST Proper Motions

Tony Sohn (Johns Hopkins U)

The Universe evolves hierarchically with small structures merging and falling in to form bigger structures. Due to its proximity, the Local Group (LG) is the best place to witness and study these hierarchical processes in action as evidenced by e.g., the many stellar streams found around the Milky Way and M31. Stellar systems in the LG have therefore become the benchmark for testing many aspects of cosmological theories. Despite the advances in both observational and theoretical areas in the last decade or so,

Astronomy Colloquium: Kristen McQuinn Wed. January 13th, 2016
11:00 am-12:00 pm

Leo P: Galaxy Evolution at the Faint-end of the Luminosity Function

Kristen McQuinn (University of Texas, Austin)

Theories of galaxy evolution have been tested by our a growing knowledge of low-mass galaxies. Much of the progress has been made studying the closest of satellites whose histories are inextricably linked to their massive host galaxy. Finding isolated galaxies to populate the faint-end of the luminosity function outside our group environment means looking farther afield – a task which has proven unavoidably problematic due to the intrinsic faintness of the systems.  One such galaxy, Leo P,

Astronomy Colloquium: Edo Berger Thu. December 10th, 2015
3:00 pm-4:00 pm

Short-Duration Gamma-Ray Bursts and the Electromagnetic Counterparts of Gravitational Wave Sources

Edo Berger (Harvard)

Gamma-ray bursts are the most luminous and energetic explosions known in the universe.  They appear in two varieties:  long- and short-duration.  The long GRB result from the core-collapse of massive stars, but until recently the origin of the short GRBs was shrouded in mystery.  In this talk I will present several lines of evidence that point to the merger of compact objects binaries (NS-NS and/or NS-BH) as the progenitor systems of short GRBs.  Within this framework, the observational data allow us to determine the merger rate of these systems as input to Advanced LIGO,

Astronomy Colloquium: Kevin Croxall Wed. December 2nd, 2015
11:00 am-12:00 pm

Oxygen in the Local Universe: Establishing Order through CHAOS

Kevin Croxall (OSU)

The metal content of a galaxy is one of the most important properties used
to distinguish between viable evolutionary scenarios and strongly influences
many of the physical processes in the ISM. An absolute and robust
calibration of extragalactic metallicities is essential in constraining
models of chemical enrichment, chemical evolution, and the cycle of baryons
in the cosmos. Despite this strong dependence on abundance, the calibration
of nebular abundances from nebular emission lines remains uncertain.
Different calibrations of the abundance scale require different assumptions,

Astronomy Colloquium: Jennifer Johnson Thu. November 12th, 2015
3:00 pm-4:00 pm

The Secret Lives of Stars: Galactic History from the APOGEE Survey

Jennifer Johnson (Ohio State University)

The history of a galaxy can be traced through its stars: their compositions, their ages, and their motions. The Milky Way provides an ideal case for performing detailed Galactic archaeology to investigate the evolution of spiral galaxies. The SDSS-APOGEE spectroscopic survey, using a high-resolution, multi-object NIR spectrograph, has observed ~150,000 stars in the Galaxy, with particular emphasis on red giants in the Kepler field and in the dust-obscured regions of the disk and bulge.  I will discuss how we are using spectroscopic and asteroseismic results to understand metallicity gradients, 

Astronomy Colloquium: Benoit Famaey Wed. October 21st, 2015
11:00 am-12:00 pm

Galactoseismology in the Milky Way

Benois Famaey, CNRS/Strasbourg

Current Galactic dynamical models still often rely on the zeroth order assumptions of a smooth time-independent and axisymmetric gravitational potential. First order perturbed models are those trying to isolate the effects of one main perturber, such as the bar or the spiral arms. In this talk, we show how a single internal perturber can generate horizontal and vertical bulk motions, in the form of “galactoseismic” oscillation modes. We also show that non-linear couplings can be present when multiple perturbers are taken into account simultaneously. We argue that,

Astronomy Colloquium: Frank Summers Wed. October 14th, 2015
11:00 am-12:00 pm

Frank Summers (STScI)

Truth and Beauty in Astronomy Visualization

The presentation of complex scientific ideas demands both precision and detail. The interpretation of even graphical representations generally requires specialized knowledge. Public-level visuals are difficult, and risk becoming over-simplified cartoon versions.

Astronomy, however, has gained favor with the public for its awe-inspiring images from the Hubble Space Telescope and other observatories. That visual splendor attracts a wide audience, creating a much smoother and natural entry into scientific topics.

Dr. Summers follows this path in creating astronomy visualizations that both engage and inform the public.

Astronomy Colloquium: Gail Zasowski Wed. September 30th, 2015
11:00 am-12:00 pm

Gail Zasowski (Johns Hopkins University)

New Tools for Galactic Archaeology from the Milky Way

One of the critical components for understanding galaxy evolution is understanding the Milky Way Galaxy itself — its detailed structure and chemodynamical properties, as well as fundamental stellar physics, which we can only study in great detail locally.  This field is currently undergoing a dramatic expansion towards the kinds of large-scale statistical analyses long used by the extragalactic and other communities, thanks in part to the enormous influx of data from multiple large space- and ground-based surveys.  I will describe the Milky Way and Local Group in the context of general galaxy evolution and highlight some recent developments in Galactic astrophysics that take advantage of these big data sets and analysis techniques. 

Astronomy Colloquium: David Merritt Wed. September 9th, 2015
11:00 am-12:00 pm

How Things Get Into (Supermassive) Black Holes

David Merritt, Rochester Institute of Technology

Gas near the center of a galaxy can find its way into the central black hole without much difficulty, but stars need to be nudged. The so-called “loss-cone problem” is well understood in the case of random gravitational encounters between the stars. But sufficiently close to a nuclear black hole, classical loss-cone theory breaks down, for two reasons: the orbits are quasi-Keplerian, and so maintain their orientations for many periods, violating the assumption of randomness; and general relativity begins to become important.

Astronomy Colloquium: Michelle Collins Wed. September 2nd, 2015
11:00 am-12:00 pm

The faintest galaxies as probes of cosmology and galactic evolution

Michelle Collins (Yale)

As the faintest galaxies we are able to observe in the Universe, the dwarf spheroidals can be thought of as the fundamental galactic unit. Within our Local Group, we are able to study these objects in extremely high detail, resolving their mass profiles, chemistries, and evolutionary histories. These measurements have led to several surprising results. One is that the masses of these systems appear to be lower than predicted by cold dark matter simulations. Additionally, dwarf galaxies are not distributed isotropically around their hosts,

Dynamical Evolution of Very Young Stellar Sub-Cluster Fri. April 17th, 2015
11:00 am-1:00 pm

Dynamical Evolution of Very Young Stellar Sub-Clusters

Alison Sills, McMaster University

Recent observations of massive, young, nearby star-forming complexes are starting to probe the detailed structure of newly-forming star clusters. In particular, the MYStIX collaboration (Feigelson et al. 2013) have an extensive census of stars in 20 such regions, probing down to low masses and through significant interstellar extinction. Early results suggest that most star clusters form from a number of distinct subclusters, and that those subclusters themselves have interesting stellar age and mass distributions. In this talk, I will discuss results from a project to dynamically model very young,

Adventures in Data Science: An Astronomer Takes the Road Ever-More-Often Traveled By Wed. April 1st, 2015
11:00 am-1:00 pm

Adventures in Data Science: An Astronomer Takes the Road Ever-More-Often Traveled By

Craig Rudick, University of Kentucky

About two years ago I left my Astronomy postdoc position for a job in the “real” world. Since then I’ve been a Data Scientist at the University of Kentucky (in the IT Department on the staff/business side), analyzing UK’s internal data on students, faculty, classes, and other business operations. The first half of my talk will be about career issues: what a data scientist is, how and why I became one, lessons learned from job hunting, transferrable skills for students (and their advisors) to focus on,

Interpreting Dwarf Galaxy Observations with Realistic Simulations Wed. March 18th, 2015
11:00 am-1:00 pm

Interpreting Dwarf Galaxy Observations with Realistic Simulations

Alyson Brooks, Rutgers University

The cosmological model based on cold dark matter (CDM) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our Universe. However, at smaller scales, dwarf galaxy observations have long presented a challenge to CDM galaxy formation theory. Recently, high resolution cosmological simulations that include baryonic physics within a CDM context have finally been able to successfully reproduce many of the characteristics of dwarfs, including those characteristics that challenged CDM theory. I will present results from simulations of both isolated and satellite dwarf galaxies,

The First Stars and Galaxies: The Run-up to the JWST Wed. March 4th, 2015
11:00 am-1:00 pm

The First Stars and Galaxies: The Run-up to the JWST

Volker Bromm, University of Texas, Austin

How and when did the cosmic dark ages end? I discuss the physics of how the first stars and galaxies formed, within the context of cosmological structure formation. I will address their feedback on the pristine intergalactic medium, and describe ways to probe their signature with next generation facilities. I will identify the key processes and outline the major remaining uncertainties.

What do the smallest galaxies tell us about dark matter? Wed. February 11th, 2015
11:00 am-1:00 pm

What do the smallest galaxies tell us about dark matter?

Matt Walker, Carnegie Mellon University

I will discuss how to translate stellar kinematics observed in the nearest, smallest and and ‘darkest’ galaxies into a test of the standard hypothesis that dark matter consists of ‘cold’ and ‘collisionless’ (i.e., weakly interacting) particles. This model now seems to require that baryon-driven processes (e.g., energetic feedback from supernova explosions) alters the internal structure of galactic dark matter halos systematically with respect to predictions derived from cosmological N-body simulations. I will discuss future work that will let us judge whether such reconciliation is energetically feasible.

Orion as a Laboratory of Protostellar Evolution: Results from the Herschel Orion Protostar Survey Wed. February 4th, 2015
11:00 am-1:00 pm

Orion as a Laboratory of Protostellar Evolution: Results from the Herschel Orion Protostar Survey

Tom Megeath, University of Toledo

The Orion molecular clouds are a remarkable laboratory for studying star formation across the mass spectrum and across the full range of environments in which stars form, from crowded clusters containing massive stars to relatively isolated low mass star formation. I will present results from the Herschel Orion Protostar Survey, or HOPS, a study of over 300 protostar in the Orion clouds with the Herschel, Spitzer, Hubble and APEX telescopes. The goal of this study is to study low to intermediate mass protostars in the Orion molecular clouds (but outside the Orion Nebula) from the earliest phases through the termination of mass infall.

Mercury: New views from MESSENGER Wed. January 21st, 2015
11:00 am-1:00 pm

Mercury: New views from MESSENGER

Steve Hauck, Earth, Environmental, and Planetary Sciences, CWRU

More than 35 years after Mariner 10 made its third and final flyby of the planet Mercury MESSENGER (short for MErcury, Surface, Space ENvironment, GEochemistry, and Ranging) became the first spacecraft to orbit the planet in March of 2011. Among the primary goals of the MESSENGER mission are to map its surface, determine the composition of the planet and its exosphere, and to constrain the structure of its interior and the nature of the planetary magnetic field. We will discuss highlights of some of MESSENGER’s major discoveries and talk about the upcoming end of the mission.

Probing Cosmic Acceleration with the Dark Energy Survey Thu. December 11th, 2014
4:00 pm-5:00 pm

Probing Cosmic Acceleration with the Dark Energy Survey

Josh Frieman, University of Chicago / FermiLab

The Nobel Prize in Physics for 2011 was awarded for the discovery that the expansion of the Universe is accelerating. Yet the physical origin of cosmic acceleration remains a mystery. The Dark Energy Survey (DES) aims to address the questions: why is the expansion speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? If dark energy, is it the energy density of the vacuum (Einstein’s cosmological constant) or something else?

Globular Cluster Streams as Galactic High-Precision Scales Wed. November 19th, 2014
11:00 am-1:00 pm

Globular Cluster Streams as Galactic High-Precision Scales

Andreas Küpper, Columbia University

Tidal streams are promising probes of the gravitational potential of the Milky Way and of the clumsiness of its dark-matter halo. We model the tidal stream of the Milky Way globular cluster Palomar 5 (Pal 5), and show that the unique geometry of the problem yields powerful constraints on the model parameters characterizing the Local Standard of Rest (LSR), the Milky Way and Pal 5 itself. Using only SDSS data and a few radial velocities from the literature, we find that the distance of the Sun from the Galactic Center is 8.30+/-0.25 kpc,

Choose Your Own Adventure: Multiplicity of Planets among the Kepler M Dwarfs Wed. November 12th, 2014
11:00 am-1:00 am

Choose Your Own Adventure: Multiplicity of Planets among the Kepler M Dwarfs

Sarah Ballard, University of Washington

The Kepler data set has furnished more than 130 exoplanetary candidates orbiting M dwarf hosts, nearly half of which reside in multiply transiting systems. I investigate the proposition of self-similarity in this sample, first posited by Swift et al. (2013) for the analysis of the five-planet system orbiting the small star Kepler-32. If we compare the predictions of one single mode of planet multiplicity and coplanarity against the Kepler sample, we can test whether we replicate the multi-planet yield of Kepler.

A Tale of Three Neutrinos Wed. October 29th, 2014
11:00 am-1:00 am

A Tale of Three Neutrinos

Derek Fox, Penn State University

I will discuss recent work to identify the brightest sources of high-energy (e_nu > TeV) neutrinos in the cosmos, those amenable to detection by IceCube, ANTARES, and other high-energy neutrino facilities. In our first tale, a neutrino produced in the high energy-density, high Lorentz-factor outflow of a gamma-ray burst arrives in coincidence with the high-energy photons from that event. While these photons might trigger a burst detection by Swift or another GRB mission, they might alternatively fail to trigger; I will discuss how the Astrophysical Multimessenger Observatory Network under development at Penn State would help to identify these subthreshold coincidences.

Do astronomical data contradict the existence of dynamically relevant particle cold or warm dark matter? Wed. October 8th, 2014
11:00 am-1:00 pm

Do astronomical data contradict the existence of dynamically relevant particle cold or warm dark matter?

Pavel Kroupa, University of Bonn

The dual-dwarf-galaxy theorem, according to which two types of galaxies must exist and which must be true in the standard model of cosmology, appears to be ruled by astronomical data: both types of dwarf galaxy, those with putative exotic dark matter and those known to not contain dark matter even if it were to exist, cannot be distinguished by observation. Furthermore, the arrangement of satellite galaxies in rotating disk-like vast near-polar structures around the Milky Way and Andromeda galaxies and the frequent occurrence of anisotropic flattened satellite populations around major galaxies,

Lifting the Dusty Veil: Understanding the Stellar Structure of Spiral Disks Fri. September 26th, 2014
12:30 pm-2:30 pm

Lifting the Dusty Veil: Understanding the Stellar Structure of Spiral Disks

Andrew Schechtman-Rook, University of Wisconsin

Measuring the vertical distribution of starlight in spiral galaxies can give valuable insights on both the formation and growth of these complex systems. Unfortunately the study of such structure outside of our Milky Way is significantly hampered by the presence of interstellar dust, which acts to attenuate light in a highly complex manner. The dust is preferentially distributed near the midplane, which makes studying that region extremely difficult. Using a combination of sub-arcsecond resolution near-infrared imaging and advanced radiative transfer modeling we have probed the stellar disk structure of several nearby edge-on spiral galaxies on vertical scales of less than 100 pc.

Astrophysics’ Extreme Matter Experiments: Understanding the Diagnostics Wed. September 17th, 2014
11:00 am-1:00 pm

Astrophysics’ Extreme Matter Experiments: Understanding the Diagnostics

Chris Fryer Los Alamos National Lab

Astrophysical Transients (supernovae, gamma-ray bursts, kilanovae, …) are often hailed as ideal laboratories to study matter at high temperatures and nuclear densities. But, as with any experiment, what we can learn about the physics of extreme matter depends both on the quality of the experiment: how well we can constrain the initial conditions and how well we can tie the observed diagnostics back to the physics we wish to study. I will review the wealth of diagnostics astronomers gather in astrophysical transients and discuss how these are used to improve our understanding of extreme states of matter

Testing Galaxy Formation with Clustering Statistics and ΛCDM Halo Models at z=0-1 Wed. September 10th, 2014
11:00 am-1:00 pm

Testing Galaxy Formation with Clustering Statistics and ΛCDM Halo Models at z=0-1

Ramin Skibba, UC San Diego

Galaxies form and evolve in particular environments of the cosmic web, which consists of a variety of filaments and knots, as well as voids and underdense regions. The influence of a galaxy’s environment on its evolution has been studied and compared extensively in the literature, although differing techniques are often used to define ‘environment.’ I will begin by assessing measures of environmental correlations using mock galaxy catalogs. I will introduce a new method for quantifying environmental correlations,


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