Abstract We present a spectroscopic and imaging analysis of the z gal ≈ 1.1334 ultrastrong Mg ii absorption system identified in the Very Large Telescope/UVES spectrum of a background quasar located at ρ ≈ 18 kpc from a star-forming galaxy. Low-ionization metal lines like Mg i , Fe ii , and Ca ii are also detected for this absorber. The H I lines are outside of the wavelength coverage. The Mg ii has a rest-frame equivalent width of W r (2796) = 3.185 ± 0.032 Å, with the absorption spread across Δ v ≈ 460 km s −1 in several components. A component-by-component ionization modeling shows several of these components having solar and higher metallicities. The models also predict a total h i column density of log N ( H I ) / cm − 2 ≈ 22.5 , consistent with ultrastrong Mg ii absorbers being sub–damped Ly α and damped Ly α systems. The absorber is well within the virial radius of the nearest galaxy, which has a stellar mass M * = 4.7 × 10 10 M ⊙ , and a star formation rate of ≈8.3 M ⊙ yr −1 . The absorption is along the projected major axis of the galaxy with a velocity spread that is wider than the galaxy’s disk rotation. From the kinematic analysis of the absorber and the galaxy, the origin of the absorption can be attributed to a combination of circumgalactic gas structures, some corotating with the disk and the rest moving at line-of-sight velocities outside of the disk rotation.
Udhwani et al. (Tue,) studied this question.
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