Department of Astronomy & Physics

Colloquia & Current Events 2015 - 2016

Colloquia Abstracts
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Archived Colloquia 2015-16

Archived Colloquia 2014-15

Archived Colloquia 2013-14

Galactic Archaeology Near and Far: Using Chemical Abundances of Globular Cluster Stars to Probe Galaxy Formation

Speaker: Dr. Charli Sakari (University of Washington)
Time: September 30, 2016 - 3:00 PM
Location: Atrium 101


Globular star clusters (GCs) are found around nearly every galaxy in the local universe.  GCs are thought to form in every major burst of star formation, and they are expected to follow the properties of a galaxy's field stars (those stars that are not in clusters).  Observations of GCs can therefore be used to unravel a galaxy's assembly history, including when and where a GC may have formed (e.g., in a dwarf galaxy that was later accreted by a larger galaxy).  In this talk I will review the techniques that are used to observe GCs, focusing on spectroscopic techniques that provide detailed chemical abundances of GC stars.  I will discuss applications to GCs in the Milky Way Galaxy and beyond, focusing on the GC population of the Milky Way's nearest massive galaxy, M31.  I will present detailed abundances from optical and infrared high resolution spectroscopy and discuss what these
abundances reveal about M31's assembly history.  The wider importance of these results for cosmology and fundamental physics will then be discussed.


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At the Edge: Recent Highlights from the Frontier Fields Program

Speaker: Dr. Gabriel Brammer (Space Telescope Science Institute, Baltimore, MD) 
Time: October 7, 2016 - 3:00 PM
Location: Atrium 101


The Frontier Fields Program has recently completed its ambitious observing campaign comprising 840 orbits and 1000 hours of the Hubble and Spitzer Space Telescopes, respectively. Imaging six deep fields around massive lensing clusters, the FF program will reveal the population of galaxies at redshifts 5--10 that are 10–-50 times fainter intrinsically than any presently known and it will help to solidify our understanding of the structures, stellar masses and star formation histories of faint galaxies across most of the age of the universe, down to, and including, the redshifts of the targeted galaxy clusters. I will highlight a number of recent discoveries made from the FF images and associated spectroscopic followup observations, including galaxy candidates discovered at z>8, gravitationally lensed dusty star-forming galaxies detected at far-infrared wavelengths with ALMA and the LMT, and the remarkable multiply-imaged supernova "Refsdal", a Type-II explosion at z=1.49 that has provided a unique and valuable tool for testing lensing and cluster dark matter models.


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The Evolution of Quasars with Cosmic Time

Speaker: Dr. Michael Strauss (Princeton University)
Time: October 14, 2016 - 3:00 PM
Location: Atrium 101


While the luminosity and mass distributions of quasars have evolved dramatically with cosmic time, the physical properties of quasars of a given luminosity are remarkably independent of redshift.  I will describe recent results on the spectra of luminous quasars, the dark matter halos in which they sit, and the intergalactic medium of their host galaxies, that are essentially indistinguishable from moderate redshifts to z>6.    Dust obscuration is another theme in quasar studies; an appreciable fraction of the growth of black holes may be hidden at optical wavelengths by dust.  I will describe searches for obscured quasars at high redshift and low, and studies of their demographics and physical properties.  I will conclude the talk with a discussion of future surveys, including the next generation of wide-field imaging and spectroscopic surveys with the 8.2-meter Subaru Telescope.


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Undergrad Symposium

Speaker: Undergrad Research Assistants
Time: September 9, 2016 - 1:00 PM
Location: Sobey 265


OpenStars: More fun in the new world

Speaker: Dr. Ian Short (Saint Mary's University)
Time: September 16, 2016 - 3:00 PM
Location: Atrium 101


This presentation and web-app demonstration will be less technical than a typical astronomy colloquium and is appropriate for a more general audience interested in scientific computing web applications.  The current goal of the OpenStars project is to deploy a general, open-ended stellar atmospheric, spectrum, and exo-planetary system modelling and visualization code as an open source web application, and to implement the modelling in a way that is rapidly responsive on common-place low performance personal computing devices.  GrayStar implements the core physical modeling in client-side JavaScript and has been developed significantly since it was last presented at SMU.  GrayStarServer implements the core physical modeling in server-side Java and performs spectrum synthesis based on a comprehensive atomic line list.  In both cases the user interface (UI), post-processing, and visualization are implemented in JavaScript and in HTML5, feature intuitive renderings of direct observables, and will work on any web browser on any platform.  These apps serves as public virtual science exhibits, and as pedagogical apparatus for properly physics-based parameter perturbation experiments and demonstrations is stellar astronomy and astrophysics.  As a pure JavaScript deployment, GrayStar turns any web browser into a computational astrophysics lab through the developer console, and entices students to contribute to the project on their own initiative.  I will perform a variety of pedagogically crucial demonstrations with both apps.   Both the physics engines and the UIs are suitable for indefinite further development at the undergraduate, graduate, and PDF level in astronomy and in computing science.   See .


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