Seminar by Farhanul Hasan, New Mexico State
Galaxies are connected to each other by the filaments and nodes of the cosmic web, but the physical impact of this connection remains unclear. I will present our recent and ongoing studies of how the cosmic web affects galaxy formation across cosmic time. First, we constructed the cosmic web structure from the distribution of galaxies in the IllustrisTNG (TNG100) cosmological simulations using the widely-used DisPerSE framework and measured the distance of a galaxy to the nearest cosmic web node and filament. We found that proximity to these structures quenches star formation (SF) at low redshifts (z<2), especially in low-mass galaxies (log M*=8-9) and satellites. However, at higher redshifts (z>2), there is virtually no effect of cosmic web environment on SF in central/satellite galaxies of any mass. Most of these trends can be explained by the cosmic web-dependence of gas fraction. Next, we compare the effect of the cosmic web on the SF and HI gas fraction of galaxies between TNG and the observed CHILES survey at z~0.1-0.5. The simulations reproduce much of the observed relationships, but some notable tensions remain, possibly due to some aspect of the physical model such as galactic feedback. Finally, we leverage the cosmic density field reconstructed by the novel "slime mold"-inspired Monte Carlo Physarum Machine (MCPM) algorithm to improve upon the existing filament identification scheme in DisPerSE. This new MCPM-based method is able to identify many more faint filaments than the regular DisPerSE pipeline. The resulting cosmic web-dependence of galaxies implies that thick (prominent) filaments have a dramatically different effect on galaxy formation than do thin (faint) filaments. The MCPM method is a key component in a recently-approved HST archival proposal to understand how the cosmic web affects gas flows around galaxies observed by SDSS and other surveys.
Host: Nicholas Luber