Genevieve J. Graves et al. 2007 ApJ 671 243 doi:10.1086/522325
Genevieve J. Graves1, S. M. Faber1, Ricardo P. Schiavon2 and Renbin Yan3
Show affiliationsAlthough 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 LINERs. We use spectra of ~6000 galaxies from the 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 (σ) and by emission properties to produce high-S/N stacked spectra. The recent stellar population models of R. Schiavon 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 σ. 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 σ for all galaxies. Elemental abundance [Mg/Fe] increases modestly with σ in agreement with previous results, and [C/Fe] and [N/Fe] increase more strongly with σ than does [Mg/Fe]. [Ca/Fe] appears to be roughly solar for all galaxies. At fixed σ galaxies with fainter r-band luminosities have lower [Fe/H] and older ages but similar abundance ratios compared to brighter galaxies.
galaxies: abundances; galaxies: elliptical and lenticular, cD
Issue 1 (2007 December 10)
Received 2007 February 5, accepted for publication 2007 July 16
Genevieve J. Graves et al. 2007 ApJ 671 243
M. Erba et al 1993 Nucl. Fusion 33 1577
R Docherty et al 1991 J. Phys. D: Appl. Phys. 24 89
T. S. Boyajian et al. 2005 ApJ 621 978
L Turban 1991 J. Phys. A: Math. Gen. 24 L1119
Zhou Yi-Yang and Zhao Min-Guang 1987 J. Phys. C: Solid State Phys. 20 5097
K A Mort et al 1999 J. Phys.: Condens. Matter 11 3967
A R McGurn 2009 J. Phys.: Condens. Matter 21 485302
Andrew L Goertzen et al 2002 Phys. Med. Biol. 47 4315
M A Fortes and P I C Teixeira 2003 J. Phys. A: Math. Gen. 36 5161