A Dusty Mg~II absorber Associated with the Quasar SDSS J003545.13+011441.2

TL;DR

This study reports the discovery of a dusty Mg II absorber associated with a quasar at redshift 1.55, characterized by significant dust depletion and a tentative 2175-Å extinction feature, using SDSS and Keck data.

Contribution

It presents the first detailed analysis of a dusty Mg II absorber with metal abundance measurements and a novel simulation method to detect the 2175-Å dust extinction bump.

Findings

Detected significant dust depletion in the absorber.

Measured column densities of multiple metal species.

Tentative 2σ detection of the 2175-Å extinction feature.

Abstract

We report on a dusty Mg~II absorber associated with the quasar SDSSJ003545.13+011441.2 (hereafter J0035+0114) at $z$=1.5501, which is the strongest one among the three Mg~II absorbers along the sight line of quasar. The two low redshift intervening absorbers are at $z$=0.7436, 0.5436, respectively. Based on the photometric and spectroscopic data of Sloan Digital Sky Survey (hereafter SDSS), we infer the rest frame color excess E(\bv) due to the associated dust is more than 0.07 by assuming a Small Magellanic Cloud (hereafter SMC) type extinction curve. Our follow-up moderate resolution spectroscopic observation at the 10-m Keck telescope with the ESI spectrometer enable us to reliably identify most of the important metal elements, such as Zn, Fe, Mn, Mg, Al, Si, Cr, and Ni in the associated system. We measure the column density of each species and detect significant dust depletion. In addition, we develop a simulation technique to gauge the significance of 2175-{\AA} dust absorption bump on the SDSS quasar spectra. By using it, we analyze the SDSS spectrum of J0035+0114 for the presence of a associated 2175-{\AA} extinction feature and report a tentative detection at $\sim$2$\sigma$ significant level.