Informal lunch talks on current research projects are held on Mondays at 12:30pm in the Astronomy Conference Room (AY 119). Pizza is provided, for a modest contribution ($2.00 per slice, from Zeffiro).
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Dark Sky Images
Ken, an retired engineer, is a highly technically skilled and artistic
astrophotographer. He will be sharing some of his work and elaborating on
the technical methods and processing techniques he applies to obtain his
unique and enhanced images. You can see Ken’s work at:
Galaxy Evolution in High Definition Via Gravitational Lensing
Dr. Jane Rigby
Deputy Project Scientist for JWST, NASA Goddard Space Flight Center
Abstract: In hundreds of known cases, “gravitational lenses” have deflected, distorted, and amplified images of galaxies or quasars behind them. As such, gravitational lensing is a way to “cheat” at studying how galaxies evolve: lensing can magnify galaxies by factors of 10–100 times, transforming them from objects we can barely detect to bright objects we can study in detail. For such rare objects, we are studying how galaxies formed stars at redshifts of 1–4, the epoch when most of the Universe’s stars were formed. For lensed galaxies, we can obtained spectral diagnostics that are currently unavailable for the distant universe, but will become routine with next-generation telescopes.
In particular, I’ll discuss MEGaSaURA, The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas, which comprises high signal-to-noise, medium spectral resolution (R~3300) spectra of 15 extremely bright gravitationally lensed galaxies at redshifts of 1.6<z<3.6. The sample, drawn from the SDSS Giant Arcs Survey, are many of the brightest lensed galaxies known. The MEGaSaURA spectra reveal a wealth of spectral diagnostics: absorption from the outflowing wind; nebular emission lines that will be key diagnostics for JWST, GMT, and TMT; and photospheric absorption lines and P Cygni profiles from the massive stars that power the outflow.
Title: Is Hierarchical Merging Broken?
Charles Steinhardt (Caltech, DARK)
I will describe two sharp puzzles suggesting a possible mismatch
between the current hierarchical merging paradigm and observations of
evolving galaxies. Current models predict that the z ~ 4-8 universe
should be a time in which the most massive galaxies are transitioning from
their initial halo assembly to the later baryonic evolution seen in
star-forming galaxies and quasars. Instead, massive galaxies appear to
exist impossibly early, before their halos should even have been able to
assemble. Further, small halos should have generally formed earlier than
larger halos, yet the observed hierarchy in galaxy formation is inverted,
with more massive galaxies completing their growth earlier. After
describing these puzzles, we will consider hierarchical merging is truly
inconsistent with observation or whether other explanations might be more
A .pdf of the talk can be found here.
Title: The Planetary Data System Atmospheres Node // Preparing for Visiting Prospective Graduate Students
Name: Nancy Chanover