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The circumgalactic medium (CGM) is a known reservoir of metals and star forming fuel. Most baryons in the universe are in the CGM or ICM. The baryon cycle- how metals reach the CGM from the inner regions of the galaxy and how gas from the CGM replenishes star forming activity in the inner regions- is an essential question in galaxy evolution. We seek to illuminate these processes by analyzing 2770 isolated halos in the IllustrisTNG simulation. This sample is divided into different classes of galaxy based star forming and AGN feedback, and morphology. By stacking halos of similar mass and history, we can identify correlations between galaxy history and the properties and dynamics of the surrounding gas. 

IllustrisTNG is a widely used suite of hydrodynamical simulations, but we found that most users are likely missing up to 5% of the gas mass within the virial radius of halos generated by TNG. An FoF (“friend of friends”) algorithm determines what gas in the simulation is assigned to each halo. Approximately one third of gas cells are not in any halo: this gas is called “fuzz”. However, at certain densities, temperatures, and halo-centric distances this decision becomes (perhaps necessarily) arbitrary for individual gas cells. We use a method of loading gas data that avoids this issue, and instead loads all gas in a given volume of the simulation. Preliminary findings suggest the FoF algorithm functions as a permeable, stochastic density threshold which preferentially misses low density gas. At the same time, the fuzz does not match gas of similar densities in the same region. In this poster, we compare fuzz gas and halo gas at similar radii and densities to explore the implications of this omission. 

The circumgalactic medium (CGM) is a critical repository for metals around galaxies, and serves as the meeting ground for galactic outflows and infalling material from the intergalactic medium. We study the net flow of metals through the CGM in the IllustrisTNG galaxy formation simulations, with a particular focus on the geometry and radial distribution of metal flows. Special care is taken to account for “fuzz” particles, which are often missed by traditional methods of selecting CGM particles in the Illustris simulations, but dominate the net outflow of gas around massive galaxies near the virial radius. 

ABSTRACT We present a low-frequency (170–200 MHz) search for prompt radio emission associated with the long GRB 210419A using the rapid-response mode of the Murchison Widefield Array (MWA), triggering observations with the Voltage Capture System for the first time. The MWA began observing GRB 210419A within 89 s of its detection by Swift, enabling us to capture any dispersion delayed signal emitted by this gamma-ray burst (GRB) for a typical range of redshifts. We conducted a standard single pulse search with a temporal and spectral resolution of $$100\, \mu$$s and 10 kHz over a broad range of dispersion measures from 1 to $$5000\, \text{pc}\, \text{cm}^{-3}$$, but none were detected. However, fluence upper limits of 77–224 Jy ms derived over a pulse width of 0.5–10 ms and a redshift of 0.6 < z < 4 are some of the most stringent at low radio frequencies. We compared these fluence limits to the GRB jet–interstellar medium interaction model, placing constraints on the fraction of magnetic energy (ϵB ≲ [0.05–0.1]). We also searched for signals during the X-ray flaring activity of GRB 210419A on minute time-scales in the image domain and found no emission, resulting in an intensity upper limit of $$0.57\, \text{Jy}\, \text{beam}^{-1}$$, corresponding to a constraint of ϵB ≲ 10−3. Our non-detection could imply that GRB 210419A was at a high redshift, there was not enough magnetic energy for low-frequency emission, or the radio waves did not escape from the GRB environment.