Using Metal-Rich Absorption features for identifying Relative Metal Content across Cosmic Time

We will present our research work involving the identification and subsequent cataloging of metal line absorbers in quasar (QSO) spectra. Our team works under the DESI Collaboration where DESI stands for Dark Energy Spectroscopic Instrument, a 4th generation Dark Energy and 3D mapping Instrument which is installed at the Kitt Peak National Observatory near Tucson, Arizona. Over the course of its 5 years of observation, the goal of the DESI mission is to create the largest ever catalog of Stars, Quasars, Galaxies and other extragalactic features. The wavelength coverage of DESI ranges from the visible spectrum to parts of the near-infrared spectrum.

Initially this project focused on the detection of Mg II absorption features, visible to the DESI spectrographs in a redshift range from z = 0.4 to z = 2.5. The detection and characterization of these absorption features then allows for further analysis in order to find other metal line absorbers arising from the same intervening galaxy; these lines include Fe II, C IV and SiIV. In order to identify these additional lines, we use a machine learning based algorithm designed to determine their anticipated locations and attempt to fit a gaussian profile. Then based on results from visual analysis we can report a likelihood of the additional line being well fit as well as its equivalent width, and other physical parameters. This computing is performed on NERSC or the National Energy Research Scientific Computing Servers.

The detection and characterization of these additional metal line systems will enable a greater understanding of the relative metal abundances of the Universe over a significant fraction of cosmic time.