The Deep2 Galaxy Redshift Survey: Mean Ages and Metallicities ofRed Field Galaxies at Z ~; 0.9 from Stacked Keck/Deimos Spectra

Journal Article · Thu Oct 19 04:00:00 EDT 2006 · Astrophysical Journal Letters

DOI:https://doi.org/10.1086/509074· OSTI ID:918492

Schiavon, Ricardo P; Faber, S M; Konidaris, Nicholas; Graves, Genevieve; Willmer, Christopher N.A.; Weiner, Benjamin J; Coil, AlisonL; Cooper, Michael C; Davis, Marc; Harker, Justin; Koo, David C; Newman, Jeffrey A; Yan, Renbin

As part of the DEEP2 galaxy redshift survey, we analyze absorption line strengths in stacked Keck/DEIMOS spectra of red field galaxies with weak to no emission lines, at redshifts 0.7 {approx}< z {approx}< 1. Comparison with models of stellar population synthesis shows that red galaxies at z {approx} 0:9 have mean luminosity-weighted ages of the order of only 1 Gyr and at least solar metallicities. These ages cannot be reconciled with a scenario where all stars evolved passively after forming at very high z. Rather, a significant fraction of stars can be no more than 1 Gyr old, which means that some star formation in the stacked populations continued to at least z {approx} 1:2. Furthermore, a comparison of these distant galaxies with a local SDSS sample, using stellar populations synthesis models, shows that the drop in the equivalent width of H{delta} from z {approx} 0:9 to 0.1 is less than predicted by passively evolving models. This admits of two interpretations: either each individual galaxy experiences continuing low-level star formation, or the red-sequence galaxy population from z {approx} 0:9 to 0.1 is continually being added to by new galaxies with younger stars.

• Research Organization: COLLABORATION - U.Virginia
• Sponsoring Organization: USDOE Director, Office of Science; National Aeronautics andSpace Administration
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 918492
• Report Number(s): LBNL--61824; BnR: 400409900
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2pt2 Vol. 651; ISSN ASTLAI; ISSN 0004-6388
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ABSORPTION
ASTRONOMY
GALAXIES
Galexies
SPECTRA
STARS
SYNTHESIS