In recent work, we have obtained improved measurements of the properties of the Milky Way and used the results to select a sample of Milky Way analog (MWA) galaxies from the Sloan Digital Sky Survey (SDSS) whose distributions of stellar mass and star formation rate match our Galaxy’s, incorporating all uncertainties. Relying on the Copernican assumption that the Milky Way should not be extraordinary, the colors and luminosities of the MWAs constrain the possible properties of our own Galaxy. This has enabled us to explore how our Galaxy fits in with the broader population; for instance, we can determine whether its properties are consistent with the power-law scaling relations exhibited by other spiral galaxies. The results have significant implications for the development of computational models of galaxy evolution in a cosmological context.  I will also describe follow-up work exploring the population of satellite galaxies in Milky Way-like dark matter halos.  It has been a long-standing puzzle why the Milky Way has considerably fewer satellite galaxies discovered to date than the typical number of satellite dark matter halos that would be found in a dark matter halo as massive as that which contains our Galaxy.  I will show that almost half of this ‘missing satellites’ problem can be explained by well-established ways in which our Galaxy’s dark matter halo is atypical.  Finally, if time allows I will also describe new work on the density profile of dark matter halos when mass within subhalos, which can often host individual galaxies, is not counted as part of the parent halo.  Widely-used profiles (such as Navarro Frenk and White) perform poorly at representing the smooth centrally-concentrated component of the halo, but there are simple functional forms which do better.

Zoom recording: https://uky.zoom.us/rec/play/58uXDQDw95A6o5P7owEDEwzb-X3PhCXv8WevwQSdhV…

The HI-MaNGA survey is an HI (21cm line) follow-up program for the SDSS-IV MaNGA survey.  I will describe the HI-MaNGA survey, its progress to date, and future plans.  I will then present new results where we combine HI-MaNGA and MaNGA data to investigate how the global HI content of star-forming galaxies relates to the mean properties of their ISM derived from optical emission lines, including integrated equivalent width, metallicity, ionization parameter, and the relative strength of low-ionization lines such as [SII] and [OI]. This analysis allows us to understand if and how the properties of the ISM vary between the most gas-rich galaxies to the most gas-poor, and how such variations may affect their evolution.  I will also discuss how gas content relates to the nuclear ionizing source (e.g., Seyfert, LINER, HII regions) and whether we find any evidence that AGN contribute to gas deficiency in the galaxy population.

Zoom Recording: https://uky.zoom.us/rec/share/xGrDewYs7rui5ao4A-_hr_N5r8_c6mkGkiksm--I61WP-hQ8VhJn9HM8fTadgDUG.M9oUhbMc-oa1r2Nr

The enormous amount of data collected by the Dark Energy Survey (DES) provide a great opportunity to explore low surface brightness science topics, such as faint diffuse light in galaxies and galaxy clusters. In this talk, I will describe how we study diffuse intra-cluster light through stacking the images of hundreds of galaxy clusters from DES, reaching a surface brightness limit of 30 mag/arcsec^2, out to a radial distance of 1 Mpc from the cluster center. Despite their low surface brightness, our studies show that intra-cluster light is a significant component of the galaxy cluster stellar content. The stacking method has also been applied to characterizing the light profiles of luminous red galaxies, as well as studying the aureole component of the DES point spread function. Weak lensing and precision photometry calibration  methods may wish to consider these effects in the future.

Since the advent of large-area, high-quality astronomical surveys strong gravitational lensing has transitioned from a small-N to a large-N discipline. Galaxy cluster scale strong lensing, in particular, holds tremendous untapped potential. I will summarize our recent progress toward unlocking the scientific potential of large samples of strong lensing systems to address fundamental problems in astrophysics and cosmology. Focusing on recent results that highlight our sophisticated lensing analysis toolbox, I will present several pioneering measurements that lay the groundwork for future work that will use large numbers of highly magnified galaxies to answer outstanding questions about the physics of star formation and the properties of the interstellar medium in the epoch during which the Universe formed most of its stars. In addition to their value as natural telescopes, the massive structures that are responsible for the lensing action are, themselves, rare and powerful tools for testing the Lambda-CDM cosmological paradigm via the growth of structure and the mass distributions of lensing clusters.

Worsham Theater on the UK Campus Map

Presented by the Department of Physics & Astronomy, professor Sandra Faber of the University of California will speak on "Modern Gensis: The Amazing Story of our Cosmic Origins". Less than one hundred years ago, astronomers did not know about galaxies or that the Milky Way is a galaxy in a vast, frothy sea of galaxies. Today, astronomers have made remarkable progress in understanding how galaxies form in our expanding universe and the crucial role that they play in how the elements we are made of were built, and even how our planets and our solar system came to be.  This lecture will distill a century of dramatic cosmic discoveries to present a comprehensive yet digestible account of why we are here and where we are going...cosmically speaking.

Sandra Faber is a professor at the University of California, Santa Cruz, and the Interim Director of the UCO/Lick Observatory.  She is an observational astronomer with primary research interests in cosmology and galaxy formation. Some of her major discoveries include the first structural scaling law for galaxies (called the Faber-Jackson relation), the discovery of large-scale flow perturbations in the expansion of the universe, and the ubiquity of massive black holes at the centers of galaxies.  In 1984, she and three colleagues presented the first detailed treatment of galaxy formation based on “cold dark matter,” which has since become the standard paradigm for galaxy formation in the universe.  Faber was one of three astronomers who diagnosed the optical flaw in the Hubble Space Telescope, and she played a major role in its repair.  From 1994-2005 she was Principal Investigator of the DEIMOS spectrograph, a large optical multi-object spectrograph for the Keck telescope that is the most powerful instrument of its kind in the world.  She and colleagues used DEIMOS to conduct the DEEP redshift survey of the distant universe, which collected spectra of 50,000 distant galaxies and exploited the immense power of Keck to see and study galaxy formation 10 billion years back in time.  She now leads the CANDELS project, the largest project in the history of the Hubble Space Telescope, to extend our view of galaxy formation back nearly to the Big Bang.  In 2009, she was awarded the Bower Award for Achievement in Science from the Franklin Institute in Philadelphia, and in 2012 she received the Bruce Medal of the Astronomical Society of the Pacific and the Russell Prize of the American Astronomical Society, both for lifetime scientific achievement. Most recently, she received the National Medal of Science from President Obama in February 2013.