2019 HotSci at STScI
Space Telescope Science Institute (STScI)
3700 San Martin Drive
Baltimore, MD 21218
2:45 PM - 4:00 PM
Featuring Raymond Simons on The Chemical and Kinematic Transformation of Galaxies: A 10 Billion Year Retrospective and Karl Gordon on Milky Way optical and mid-IR extinction curves.
All talks are held on Wednesdays in the STScI John N. Bahcall Auditorium at 3:00 p.m. preceded by refreshments at 2:45 p.m.
Name: Raymond Simons
Title: The Chemical and Kinematic Transformation of Galaxies: A 10 Billion Year Retrospective
Abstract: The peak of cosmic star-formation at z~2, 10 billion years ago, marks a transformative period for galaxies. The mechanisms that govern the rapid mass growth of galaxies at this time are now also thought to be dynamically disruptive - (re-)shaping galaxies on short timescales. I will show how this bears out in observations. Using Hubble and Keck spectroscopy, I will show that both the distribution of gas-phase metals and the kinematic nature of galaxies at this time necessitate a disruptive and inhospitable phase of galaxy assembly in the early universe.
Name: Karl Gordon
Title: Milky Way optical and mid-IR extinction curves
Abstract: Interstellar dust extinction in the optical and mid-infrared (MIR) wavelength ranges is characterized by an overall decreasing extinction with increasing wavelength with superimposed broad extinction features. I will present work focused on measuring the spectroscopic dust extinction in these two wavelength ranges. The first study gives the first truly spectroscopic measurement of the diffuse ISM MIR extinction based on a sample of sightlines observed by the Spitzer Space Telescope. This new measurement provides the full 5-40 micron average extinction curve including profiles for the the two silicate grain diagnostic features at 10 and 20 microns. The second study uses HST/STIS spectra to perform the first systematic spectroscopic study of optical extinction in the Milky Way. This study has revealed that the Very Broad Structure in optical extinction is due to three broad extinction features, two of which have strengths that intriguingly correlate with the 2175 A extinction feature. The results of these two studies provide new constraints on dust grain properties and empirical averages useful for modeling and/or correcting for the effects of dust extinction on background sources.