Recovering the systemic redshift of galaxies from their Lyman alpha line profile. (6th April 2018)

• Record Type: Journal Article
• Authors: Verhamme, A; Garel, T; Ventou, E; Contini, T; Bouché, N; Herenz, EC; Richard, J; Bacon, R; Schmidt, KB; Maseda, M; Marino, RA; Brinchmann, J; Cantalupo, S; Caruana, J; Clément, B; Diener, C; Drake, AB; Hashimoto, T; Inami, H; Kerutt, J; Kollatschny, W; Leclercq, F; Patrício, V; Schaye, J; Wisotzki, L; Zabl, J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 478:Number 1(2018:Jul.)
• Page Start: L60
• Page End: L65
• Publication Date: 2018-04-06
• Subjects: galaxies: high-redshift -- galaxies: starburst -- galaxies: statistics -- ultraviolet: galaxies; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/sly058
• Languages: English
• ISSNs: 1745-3933

Abstract

Abstract: The Lyman alpha (Ly α) line of Hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km s −1 compared to the systemic redshift. This large offset hampers follow-up surveys, galaxy pair statistics, and correlations with quasar absorption lines when only Ly α is available. We propose diagnostics that can be used to recover the systemic redshift directly from the properties of the Ly α line profile. We use spectroscopic observations of Ly α emitters for which a precise measurement of the systemic redshift is available. Our sample contains 13 sources detected between z ≈ 3 and z ≈ 6 as part of various multi-unit spectroscopic explorer guaranteed time observations. We also include a compilation of spectroscopic Ly α data from the literature spanning a wide redshift range ( z ≈ 0–8). First, restricting our analysis to double-peaked Ly α spectra, we find a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, $V_{\rm peak}^{\rm red}$, and the separation of the peaks. Secondly, we find a correlation between $V_{\rm peak}^{\rm red}$ and the full width at half-maximum of the Ly α line. Fitting formulas to estimate systemic redshifts of galaxies with an accuracy of ≤100 km s −1, when only the Ly α emission line is available, are given for the two methods.