The Composite Spectrum of QSO Absorption Line Systems in DESI DR2
Authors
Lucas Napolitano
Adam D. Myers
Adam Tedeschi
Abhijeet Anand
Hiram K. Herrera-Alcantar
Jessica Aguilar
Steven Ahlen
Stephen Bailey
Segev BenZvi
Davide Bianchi
David Brooks
Todd Claybaugh
Andrei Cuceu
Axel de la Macorra
Arjun Dey
Biprateep Dey
Peter Doel
Andreu Font-Ribera
Jaime E. Forero-Romero
Enrique Gaztanaga
Satya Gontcho A Gontcho
Gaston Gutierrez
Julien Guy
Dick Joyce
Anthony Kremin
Martin Landriau
Laurent Le Guillou
Marc Manera
Aaron Meisner
Ramon Miquel
John Moustakas
Seshadri Nadathur
Nathalie Palanque-Delabrouille
Will Percival
Francisco Prada
Ignasi Perez-Rafols
Graziano Rossi
Eusebio Sanchez
David Schlegel
Michael Schubnell
Joesph Harry Silber
David Sprayberry
Gregory Tarle
Benjamin Alan Weaver
Rongpu Zhou
Hu Zou
Abstract
We present details regarding the construction of a composite spectrum of quasar (QSO) absorption line systems. In this composite spectrum we identify more than 70 absorption lines, and observe oxygen and hydrogen emission features at a higher signal-to-noise ratio than in any previous study. As the light from a distant quasar travels towards an observer, it may interact with the circumgalactic medium environment of an intervening galaxy, forming absorption lines. In order to maximize the signal of these absorption lines, we have selected a sample of 238,838 quasar spectra from the second data release of the Dark Energy Spectroscopic Instrument (DESI), each identified to have absorption lines resulting from such an interaction. By stacking these spectra in the restframe of the absorption, and calculating a median composite spectrum, we are able to isolate and enhance these absorption lines. We provide a full atlas of all detected absorption and emission lines as well as their fit centroids and equivalent width values. This atlas should aid in future studies investigating the compositions and physical conditions of these absorbers.
