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NOAO fundamental plane survey II: Age and metallicity along the red sequence from line-strength data

Nelan, J.E.; Smith, R.J.; Hudson, M.J.; Wegner, G.A.; Lucey, J.R.; Moore, S.A.W.; Quinney, S.J.; Suntzeff, N.B.

NOAO fundamental plane survey II: Age and metallicity along the red sequence from line-strength data Thumbnail


Authors

J.E. Nelan

M.J. Hudson

G.A. Wegner

S.A.W. Moore

S.J. Quinney

N.B. Suntzeff



Abstract

We present spectroscopic line-strength data for 4097 red-sequence galaxies in 93 low-redshift galaxy clusters and use these to investigate variations in average stellar populations as a function of galaxy mass. Our analysis includes an improved treatment of nebular emission contamination, which affects 10% of the sample galaxies. Using the stellar population models of D. Thomas and collaborators, we simultaneously fit 12 observed line-strength relations in terms of common underlying trends of age, [Z/H] (total metallicity), and [/Fe] (-element enhancement). We find that the observed line-strength relations can be explained only if higher mass red-sequence galaxies are, on average, older, more metal-rich, and more -enhanced than lower mass galaxies. Quantitatively, the scaling relations are age0.59±0.13, Z/H0.53±0.08, and /Fe0.31±0.06, where the errors reflect the range obtained using different subsets of indices. Our conclusions are not strongly dependent on which Balmer lines are used as age indicators. The derived age- relation is such that if the largest (400 km s-1) galaxies formed their stars 13 Gyr ago, then the mean age of low-mass (50 km s-1) objects is only 4 Gyr. The data also suggest a large spread in age at the low-mass end of the red sequence, with 68% of the galaxies having ages between 2 and 8 Gyr. We conclude that although the stars in giant red galaxies in clusters formed early, most of the galaxies at the faint end joined the red sequence only at recent epochs. This "downsizing" trend is in good qualitative agreement with observations of the red sequence at higher redshifts but is not predicted by semianalytic models of galaxy formation.

Citation

Nelan, J., Smith, R., Hudson, M., Wegner, G., Lucey, J., Moore, S., …Suntzeff, N. (2005). NOAO fundamental plane survey II: Age and metallicity along the red sequence from line-strength data. Astrophysical Journal, 632(1), 137-156. https://doi.org/10.1086/431962

Journal Article Type Article
Publication Date 2005-10
Deposit Date May 20, 2008
Publicly Available Date Aug 12, 2014
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 632
Issue 1
Pages 137-156
DOI https://doi.org/10.1086/431962
Keywords Galaxies, Clusters, Elliptical and lenticular, Evolution, Surveys.

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Copyright Statement
© 2005. The American Astronomical Society. All rights reserved.







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