Detecting and Characterizing Mg II absorption in DESI Survey Validation Quasar Spectra

Abstract

We present findings of the detection of Magnesium II (Mg II, λ = 2796, 2803 Å) absorbers from the early data release of the Dark Energy Spectroscopic Instrument (DESI). DESI is projected to obtain spectroscopy of approximately 3 million quasars (QSOs), of which over 99% are anticipated to be at redshifts greater than z > 0.3, such that DESI would be able to observe an associated or intervening Mg II absorber illuminated by the background QSO. We have developed an autonomous supplementary spectral pipeline that detects these systems through an initial line-fitting process and then confirms the line properties using a Markov Chain Monte Carlo sampler. Based upon a visual inspection of the resulting systems, we estimate that this sample has a purity greater than 99%. We have also investigated the completeness of our sample in regard to both the signal-to-noise properties of the input spectra and the rest-frame equivalent width (W0) of the absorber systems. From a parent catalog containing 83,207 quasars, we detect a total of 23,921 Mg II absorption systems following a series of quality cuts. Extrapolating from this occurrence rate of 28.8% implies a catalog at the completion of the five-year DESI survey that will contain over eight hundred thousand Mg II absorbers. The cataloging of these systems will enable significant further research because they carry information regarding circumgalactic medium environments, the distribution of intervening galaxies, and the growth of metallicity across the redshift range 0.3 < z < 2.5.

17 pages, 8 figures

References in corpus (13)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Circumgalactic Medium
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The Sloan Digital Sky Survey Quasar Catalog: twelfth data release
• Clustering of High Redshift ($z\ge 2.9$) Quasars from the Sloan Digital Sky Survey
• An improved measurement of the flux distribution of the Ly-alpha forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties
• Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16
• Mg II absorbers: metallicity evolution and cloud morphology
• Empirically Constrained Predictions for Metal-Line Emission from the Circumgalactic Medium
• Metal line emission from galaxy haloes at z~1
• Cool circumgalactic gas in galaxy clusters: connecting the DESI legacy imaging survey and SDSS DR16 MgII absorbers
• Strong Mg II and Fe II Absorbers at 2.2 < z < 6.0
• Intervening Mg II absorption systems from the SDSS DR12 quasar spectra

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• A Deep Search for a Strong Diffuse Interstellar Band in the Circumgalactic Medium
• DESI Mg II Absorbers: Extinction Characteristics & Quasar Redshift Accuracy
• Magnetised CGM Gas at z~1 revealed by SPICE-RACS
• Baryonic Ecosystem IN Galaxies (BEINGMgII) -- III. Cool gas reservoirs at $0.3\le z\le 1.6$ in the Dark Energy Survey