2023/11/08 by Labanya Kumar Guha, R. Srianand, Guha, Labanya Kumar +3
Physics and Astronomy · #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2311.04973
openalex publication_date 2023/11/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We report spectroscopic identification of the host galaxies of 18 ultra-strong MgII systems (USMgII) at 0.6 ≤ z ≤ 0.8. We created the largest sample by merging these with 20 host galaxies from our previous survey within 0.4 ≤ z ≤ 0.6. Using this sample, we confirm that the measured impact parameters (\rm 6.3≤ D[kpc] ≤ 120 with a median of 19 kpc) are much larger than expected, and the USMgII host galaxies do not follow the canonical \rm W2796-D anti-correlation. We show that the presence and significance of this anti-correlation may depend on the sample selection. The \rm W2796-D anti-correlation seen for the general MgII absorbers show a mild evolution at low \rm W2796 end over the redshift range 0.4 ≤ z ≤ 1.5 with an increase of the impact parameters. Compared to the host galaxies of normal MgII absorbers, USMgII host galaxies are brighter and more massive for a given impact parameter. While the USMgII systems preferentially pick star-forming galaxies, they exhibit slightly lower ongoing star-forming rates compared to main sequence galaxies with the same stellar mass, suggesting a transition from star-forming to quiescent states. For a limiting magnitude of mr < 23.6, at least 29% of the USMgII host galaxies are isolated, and the width of the MgII absorption in these cases may originate from gas flows (infall/outflow) in isolated halos of massive star-forming but not starbursting galaxies. We associate more than one galaxy with the absorber in ≥ 21% cases where interactions may cause wide velocity spread.