סמינר מאסטרנטים באסטרונומיה ובאסטרופיזיקה

Zoom: https://tau-ac-il.zoom.us/j/87230679135?pwd=Y1duRlArUkJwSnhaaXVscUU0azY3Zz09

Aharon Kakoly, TAU

The Origin of Circumgalactic UV Absorbers With Equivalent Widths of ~ 1Å

Abstract:

The circumgalactic medium (CGM) plays a vital role in galaxy evolution, regulating gas inflows and outflows. While the standard picture of the CGM consists of cool clouds embedded in a pervasive hot medium, our research challenges this view. Using FIRE cosmological simulations of Milky-Way mass galaxies, we demonstrate that the inner CGM is predominantly cool at early times, while a volume-filling hot phase forms only at a redshift 0 < z <~ 1. Before this transition, UV absorbers like Mg II and Si III exhibit high equivalent widths (~1Å), driven by saturated absorption in turbulent, cool gas. As the hot phase develops, equivalent widths decrease, and UV absorption traces dense cool clouds within the diffuse hot medium. These findings highlight how different CGM phases are shaped by turbulence and halo mass, and offer new insights into the CGM’s evolution and its observable UV absorption signatures.

Tomer Katz, TAU

Progen-it!: A Systematic Approach to Fit Core Collapse Supernova Progenitors to Models:

Abstract:

Massive stars and their explosion as supernovae dictate chemical enrichment and feedback in galaxies, as well as the formation of neutron stars and black holes. Yet, we still don't understand the basic connection between types of massive stars and types of supernovae - a connection critical also for informing stellar evolution and explosion models. The most direct way to constrain this connection is with pre-explosion images of supernova progenitors. Typically, studies compare the photometry of the progenitors to stellar evolutionary tracks, and associate the progenitor to the model with the nearest track in the H-R diagram. The results depend on the model grid being used as well as assumptions on the metallicity of the star and the distance and extinction to it. I will present a new Bayesian tool I developed to fit supernova progenitor observations to models, which produces more realistic uncertainties, reveals degeneracies between parameters, and quantifies the effects of priors. This tool can also guide future observations by determining the best combination of bands required to obtain the most constraining results. I will also show some results of running the tool on all published supernova progenitor data, with implications for the so-called "Red Supergiant Problem" and the correlation between progenitor mass and supernova explosion velocity.

מארגן הסמינר: ד"ר יהונתן שטרן