Physics & Astronomy Colloquium – Fall 2018 – Werk

Faculty & Postdoc Mini-Colloquia

Speaker: Dean Townsley (UA)
Title: Are we finally close to discovering the origins of type Ia supernovae?
Abstract: I will discuss recent results in the study of type Ia supernovae. From the
theoretical side, I will show that recent simulations demonstrate that a
particular mechanism of supernova explosion, the helium shell
double-detonation mechanism, is, in fact, likely to yield supernovae that are
spectroscopically normal type Ia supernovae. This is in contrast to previous
simulations of this mechanism, and is directly attributable to the inclusion
of more complete nuclear reactions in the simulations. From the
observational side, I will discuss the discovery of stars predicted by the
dynamically driven double degenerate double detonation (D^6) scenario in a
recent survey of the distance and motion of stars in our galaxy. Several
stars discovered are on their way out of our Galaxy, possibly being the
ejected companion stars of a star that exploded as a type Ia supernova.
These may be the long-sought compact stellar remnants of type Ia supernovae.

Speaker: Amy Jones (UA)
Title: Studying warm, diffuse gas in the outskirts of galaxies
Abstract: Surrounding most galaxies is large amount of diffuse gas that extends much farther than the galaxy. This gas is important for resolving the missing baryons problem and understanding galaxy evolution. At the disk-halo interface where the gas is falling onto or being blown away from the galaxy is a critical transition place which has been poorly studied. One component of this gas is warm and ionized, which is faint and diffuse and hence difficult to study. By stacking multiple similar galaxies, we can clearly detect this extra-planar gas out to several kpc (includes the disk-halo interface). I will introduce the SDSS-IV MaNGA survey that we use for this study and how we split this sample into many subsamples to see how the gas properties (e.g. temperature, density, ionization state) depend on the host galaxy properties (e.g. morphological type, star formation rate). I will show some preliminary results and discuss a future survey of SDSS-V, called LVM.

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CANCELED:

Speaker: Jessica Werk (University of Washington, Seattle)

Title: Why Circumgalactic Matter Matters for Galaxy Evolution

Abstract: The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the assembly and evolution of galaxies. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In the last decade, we have learned that the CGM of Milky Way mass galaxies likely contains enough material to harbor most of the metals lost in galaxy winds and to sustain star-formation for billions of years. Remarkably, this implies that most of the heavy elements on earth cycled back and forth multiple times through the Milky Way’s own CGM before the formation of the solar system. In this talk, I will describe constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state. I will conclude by posing several unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.

Speaker Biography:

Jessica Werk studies the extended gaseous components of galaxies and the role they play in galaxy formation and evolution. She is primarily an observational astronomer with expertise in optical and ultraviolet spectroscopy, and uses both ground and space-based telescopes to carry out her research. She works closely with theorists in defining observational constraints for cosmological simulations (such as those generated in the UW N-body shop), and in physically interpreting her own observations.

Professor Werk’s current research focuses on the “invisible” ionized gas of galaxies in two largely unexplored regimes: (1) the dark-matter halo and (2) the disk-halo interface. Ultimately, she would like to understand the complex galactic ecosystems in which baryons cycle through many physical phases over hundreds of kiloparsecs, from the interiors of stars to the intergalactic medium.

Outside of astronomy, she enjoys strenuous hikes up tall mountains, duplicate bridge, and singing Puccini arias to her dog.