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Past Events

Event Date Summary
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.

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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.

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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.

Continue reading… Astronomy Colloquium: Elena D’Onghia

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.

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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,

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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.

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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,

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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, has been discovered through the blind HI ALFALFA Survey.

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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,

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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,

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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, 

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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,

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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.

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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. 

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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.

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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,

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