Astronomy Talk : Studying Metals in the Circumgalactic Medium by Post-Processing

Come join us for our monthly Astronomy talk!

7:30pm to 8pm: Social time, come and mingle. We will have snacks and beverages.

Talk begins at 8pm.

Topic: Studying Metals in the Circumgalactic Medium by Post-Processing Galaxy Simulations

Speaker: Bryan Wang (The Harker School), Rishi Dange (The Harker School)

Description:
In recent decades, cosmological simulations have played an increasing role in the expert understanding of galaxy formation, but while simulations have improved dramatically, many parameters such as the strength of stellar and supernova feedback are not well determined. The circumgalactic medium (CGM), the gas outside of the galaxy disc but within the dark matter halo, could be an effective probe of feedback models due to its high ionization level and low density. However, since the CGM does not form stars and is usually detected in absorption spectra, instead of simulated telescope image comparisons, a more specialized methodology is needed. This work analyzes the CGM of many simulated galaxies using the random sampling of sightlines throughout a spherical volume surrounding them, emulating absorption spectra. We determine each sightline using two points: the starting location is chosen uniformly over the surface of the sphere and the midpoint is uniformly distributed throughout the bulk of a smaller concentric sphere. We project along this line of sight and use ionization calculation software TRIDENT to determine the column densities of ions situated in the line. Since we can make a large number of individual sightlines, many statistical properties can be examined, covering the full spectrum of redshifts, star formation histories, masses, and other macroscopic parameters of the simulated galaxies. These properties can be directly compared to observed absorption data, and can therefore help constrain the parameters of these simulations and either improve confidence in their predictions or determine what physical models need to be adjusted.

Mentors: Clayton Strawn (UCSC) and Professor Joel Primack (UCSC)