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Early Results on the Detection of Mg-II Absorption Systems in DESI Spectra

Presentation #538.03 in the session “AGN and Quasars 3”.

Published onJan 11, 2021
Early Results on the Detection of Mg-II Absorption Systems in DESI Spectra

We will present preliminary findings on the automated detection of Mg-II absorption systems in spectra observed during the DESI mission. When galaxies lie between us and a background quasar, they leave evidence of their existence by absorbing some of the quasar’s emitted light. Thus these absorption signals are perhaps the best current way of surveying the properties of extremely faint galaxies at large distances. In this current study we are searching for the Mg-II absorption feature as it appears as a doublet and is observable in the redshift range z = 0.3-2.5. As DESI will observe of order 2.5 million quasar spectra over the course of its 5-year run it presents an opportunity to create the largest ever catalog of these features. The potential applications of this catalog include studies of chemical enrichment, properties of the circumgalactic medium and galaxy clustering.

We will demonstrate using mock spectra that our secondary spectral pipeline detects Mg-II systems with high purity and completeness. Additionally, using real data, we will show how the equivalent widths of Mg-II systems evolve with redshift. A general trend of decreasing equivalent width is observed which may be of evidence of chemical enrichment over time.

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