2018/04/05 by A. Verhamme, Anne Verhamme, Thibault Garel +41 · 3 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Emission spectrum #Equivalent width #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Physics #Quasar #Redshift #Redshift survey #Spectral line #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnrasl/sly058
letter, accepted for publication in MNRAS
arxiv created 2018/04/05 · openalex publication_date 2018/04/06 · arxiv updated 2018/06/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
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.