Intervening Mg II absorption systems from the SDSS DR12 quasar spectra

Abstract

We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the twelfth data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0$\sigma$ level respectively for the two lines of the doublet. The catalogue was constrained to an absorption line redshift of 0.35 $\le$ z${}_{2796}$ $\le$ 2.3. The rest-frame equivalent width of the $\lambda$2796 line ranges between 0.2 $\le$ W${}_r$ $\le$ 6.2 $\mathring{A}$. Using Gaussian-noise only simulations we estimate a false positive rate of 7.7 per cent in the catalogue. We measured the number density $\partial N^{2796}/\partial z$ of Mg II absorbers and find evidence for steeper evolution of the systems with W${}_r\ge$ 1.2 $\mathring{A}$ at low redshifts (z${}_{2796}$ $\le$ 1.0), consistent with other earlier studies. A suite of null tests over the redshift range 0.5 $\le$ z${}_{2796}$ $\le$ 1.5 was used to study the presence of systematics and selection effects like the dependence of the number density evolution of the absorption systems on the properties of the background quasar spectra. The null tests do not indicate the presence of any selection effects in the absorption catalogue if the quasars with spectral signal-to-noise level less than 5.0 are removed. The resultant catalogue contains 36,981 absorption systems. The Mg II absorption catalogue is publicly available and can be downloaded from the link http://srini.ph.unimelb.edu.au/mgii.php

Updated references, typos; Published in MNRAS; 15 pages, 14 figures, 2 tables

References in corpus (4)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Clustering of MgII Absorption Systems at z=0.5 and Detection of Cold Gas in Massive Halos
• Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts
• The Kinematic Evolution of Strong MgII Absorbers

Cited by in corpus (5)

• Solving the conundrum of intervening strong MgII absorbers towards GRBs and quasars
• Collective properties of quasar narrow associated absorption lines
• Searching for MgII absorbers in and around galaxy clusters
• Probing the physical properties of the intergalactic medium using gamma-ray bursts
• Probing the physical properties of the intergalactic medium using blazars