Characterization of contaminants in the Lyman-alpha forest auto-correlation with DESI
Abstract
Baryon Acoustic Oscillations can be measured with sub-percent precision above redshift two with the Lyman-alpha forest auto-correlation and its cross-correlation with quasar positions. This is one of the key goals of the Dark Energy Spectroscopic Instrument (DESI) which started its main survey in May 2021. We present in this paper a study of the contaminants to the lyman-alpha forest which are mainly caused by correlated signals introduced by the spectroscopic data processing pipeline as well as astrophysical contaminants due to foreground absorption in the intergalactic medium. Notably, an excess signal caused by the sky background subtraction noise is present in the lyman-alpha auto-correlation in the first line-of-sight separation bin. We use synthetic data to isolate this contribution, we also characterize the effect of spectro-photometric calibration noise, and propose a simple model to account for both effects in the analysis of the lyman-alpha forest. We then measure the auto-correlation of the quasar flux transmission fraction of low redshift quasars, where there is no lyman-alpha forest absorption but only its contaminants. We demonstrate that we can interpret the data with a two-component model: data processing noise and triply ionized Silicon and Carbon auto-correlations. This result can be used to improve the modeling of the lyman-alpha auto-correlation function measured with DESI.
Keywords
Cite
@article{arxiv.2404.03003,
title = {Characterization of contaminants in the Lyman-alpha forest auto-correlation with DESI},
author = {J. Guy and S. Gontcho A Gontcho and E. Armengaud and A. Brodzeller and A. Cuceu and A. Font-Ribera and H. K. Herrera-Alcantar and N. G. Karaçaylı and A. Muñoz-Gutiérrez and M. Pieri and I. Pérez-Ràfols and C. Ramírez-Pérez and C. Ravoux and J. Rich and M. Walther and M. Abdul-Karim and J. Aguilar and S. Ahlen and A. Bault and D. Brooks and T. Claybaugh and R. de la Cruz and A. de la Macorra and P. Doel and K. Fanning and J. E. Forero-Romero and E. Gaztañaga and A. X. Gonzalez-Morales and G. Gutierrez and C. Hahn and K. Honscheid and S. Juneau and R. Kehoe and D. Kirkby and T. Kisner and A. Kremin and A. Lambert and M. Landriau and L. Le Guillou and M. Manera and P. Martini and A. Meisner and R. Miquel and P. Montero-Camacho and J. Moustakas and E. Mueller and A. D. Myers and J. Nie and G. Niz and N. Palanque-Delabrouille and W. J. Percival and C. Poppett and M. Rezaie and G. Rossi and E. Sanchez and D. Schlegel and M. Schubnell and H. Seo and J. Silber and D. Sprayberry and T. Tan and G. Tarlé and M. Vargas-Magaña and H. Zou},
journal= {arXiv preprint arXiv:2404.03003},
year = {2025}
}
Comments
32 pages, 12 figures