Strong nebular emissions associated with MgII absorptions detected in the SDSS spectra of background quasars (2407.04096v2)

Abstract: We present long-slit spectroscopic observations of 40 Galaxy On Top Of Quasars (GOTOQs) at ${0.37 \leqslant z \leqslant 1.01}$ using the South African Large Telescope. Using this and available photometric data, we measure the impact parameters of the foreground galaxies to be in the range of 3$-$16 kpc with a median value of 8.6 kpc. This is the largest sample of galaxies producing MgII absorption at such low impact parameters. These quasar-galaxy pairs are ideal for probing the disk-halo interface. At such impact parameters, we do not find any significant anti-correlation between rest equivalent width (REW) of CaII, MnII, FeII, MgII, and MgI absorptions and impact parameters. These sight lines are typically redder than those of strong MgII absorbers, with the color excess, E(B$-$V) for our sample ranging from $-$0.191 to 0.422, with a median value of 0.058. In the E(B$-$V) vs. W${3935}$ plane, GOTOQs occupy the same region as CaII absorbers. For a given E(B$-$V), we find larger W${3935}$ than what has been found in the Milky Way, probably due to a smaller dust-to-gas ratio in GOTOQs. Galaxy parameters could be measured for twelve cases, and their properties seem to follow the trends found for strong MgII absorbers. Measuring the host galaxy properties for the full sample using HST photometry or AO-assisted ground-based imaging is important to gain insights into the relationship between the stellar mass of galaxies and the metal line REW distributions at low impact parameters.