Neutral magnesium as a probe of high column density QSO absorbers.

QSOs, providing distant, luminous sources of radiation, provide a means to detect gas by absorption in the interstellar and intergalactic medium. Of particular interest to astronomers studying metal line systems in lines of sight to QSOs are the classes characterized by their neutral hydrogen column density known as Damped Lyman-a systems (DLAs) and Sub-damped Lyman-a systems (Sub-DLAs). DLAs and Sub-DLAs provide a means to probe the detailed abundance and dust content of the Universe at high redshift, revealing the evolving presence of elements heavier than hydrogen and helium. Here, we present a correlation between ionization and metallicity as indicated by the abundance ratios [Si II / Mg I] and [Zn II / HI], respectively, in such systems at redshift z~0.5-2.7. The abundances used were drawn from the literature where reported. However, where elemental abundances were omitted in the literature, we profile fit those spectra to obtain them. We believe that this correlation, if proven valid, could provide another tracer of evolution of elements throughout the history of the Universe

Black hole feedback and the evolution of massive early-type galaxies

Observationally, constraining the baryonic cycle within massive galaxies has proven to be quite difficult. In particular, the role of black hole feedback in regulating star formation, a key process in our theoretical understanding of galaxy formation, remains highly debated. We present here observational evidence showing that, at fixed stellar velocity dispersion, the temperature of the hot gas is higher for those galaxies hosting more massive black holes in their centers. Analyzed in the context of well-established scaling relations, particularly the mass-size plane, the relation between the mass of the black hole and the temperature of the hot gas around massive galaxies provides further observational support to the idea that baryonic processes within massive galaxies are regulated by the combined effects of the galaxy halo virial temperature and black hole feedback, in agreement with the expectations from the EAGLE cosmological numerical simulation.Comment: 10 pages, 5 figure, accepted for publication in MNRAS

Searching for the Imprints of AGN Feedback on the Lyman Alpha Forest Around Luminous Red Galaxies

We explore the potential of using the low-redshift Lyman-$\alpha$ (Ly$\alpha$) forest surrounding luminous red galaxies (LRGs) as a tool to constrain active galactic nuclei (AGN) feedback models. Our analysis is based on snapshots from the Illustris and IllustrisTNG simulations at a redshift of $z=0.1$. These simulations offer an ideal platform for studying the influence of AGN feedback on the gas surrounding galaxies, as they share the same initial conditions and underlying code but incorporate different feedback prescriptions. Both simulations show significant impacts of feedback on the temperature and density of the gas around massive halos. Following our previous work, we adjusted the UV background in both simulations to align with the observed number density of Ly$\alpha$ lines ($\rm dN/dz$) in the intergalactic medium and study the Ly$\alpha$ forest around massive halos hosting LRGs, at impact parameters ($r_{\perp}$) ranging from 0.1 to 100 pMpc. Our findings reveal that $\rm dN/dz$, as a function of $r_{\perp}$, is approximately 1.5 to 2 times higher in IllustrisTNG compared to Illustris up to $r_{\perp}$ of $\sim 10$ pMpc. To further assess whether existing data can effectively discern these differences, we search for archival data containing spectra of background quasars probing foreground LRGs. Through a feasibility analysis based on this data, we demonstrate that ${\rm dN/dz} (r_{\perp})$ measurements can distinguish between feedback models of IllustrisTNG and Illustris with a precision exceeding 12$\sigma$. This underscores the potential of ${\rm dN/dz} (r_{\perp})$ measurements around LRGs as a valuable benchmark observation for discriminating between different feedback models.Comment: 21 pages (including 4 page appendix), Submitted to MNRA