2007/07/16 by Genevieve J. Graves, S. M. Faber, Sandra M. Faber +2 · 3 citations
Chemistry · Mathematics · Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Biochemistry #Biology #Chemistry #Evolutionary biology #Function (biology) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Line (geometry) #Mathematics #Physics #Sequence (biology) #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/522325
25 pages, 17 figures, Accepted for publication in ApJ as of 16 July 2007; acceptance status updated, paper unchanged
arxiv created 2007/07/16 · openalex publication_date 2007/12/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Although the spectrum of a prototypical early-type galaxy is assumed to lack emission lines, a substantial fraction (likely as high as 30%) of nearby red sequence galaxy spectra contain emission lines with line ratios characteristic of low ionization nuclear emission-line regions (LINERs). We use spectra of ~6000 galaxies from the Sloan Digital Sky Survey (SDSS) in a narrow redshift slice (0.06 < z < 0.08) to compare the stellar populations of red sequence galaxies with and without LINER-like emission. The spectra are binned by internal velocity dispersion and by emission properties to produce high S/N stacked spectra. The recent stellar population models of R. Schiavon (2007) make it possible to measure ages, [Fe/H], and individual elemental abundance ratios [Mg/Fe], [C/Fe], [N/Fe], and [Ca/Fe] for each of the stacked spectra. We find that red sequence galaxies with strong LINER-like emission are systematically 2-3.5 Gyr (10-40%) younger than their emission-free counterparts at the same velocity dispersion. This suggests a connection between the mechanism powering the emission (whether AGN, post-AGB stars, shocks, or cooling flows) and more recent star formation in the galaxy. We find that mean stellar age and [Fe/H] increase with velocity dispersion for all galaxies. Elemental abundance [Mg/Fe] increases modestly with velocity dispersion in agreement with previous results, and [C/Fe] and [N/Fe] increase more strongly with velocity dispersion than does [Mg/Fe]. [Ca/Fe] appears to be roughly solar for all galaxies. At fixed velocity dispersion, galaxies with fainter r-band luminosities have lower [Fe/H] and older ages but similar abundance ratios compared to brighter galaxies.