The 2dF-SDSS LRG and QSO survey: the star formation histories of luminous red galaxies

Roseboom, Isaac G., Pimbblet, Kevin A., Drinkwater, Michael J., Cannon, Russell D., De Propris, Roberto, Edge, Alastair C., Eisenstein, Daniel J., Nichol, Robert C., Smail,Ian, Wake, David A., Bland-Hawthorn, Joss, Bridges, Terry J., Carson, Daniel, Colless, Matthew, Couch, Warrick J., Croom, S. M., Driver, S. P., Hewett, P. C., Loveday, J., Ross, N., Schneider, D. P., Shanks, T., Sharp, R. G. and Weilbacher, P (2006) The 2dF-SDSS LRG and QSO survey: the star formation histories of luminous red galaxies. Monthly Notices Of The Royal Astronomical Society, 373 1: 349-360. doi:10.1111/j.1365-2966.2006.11024.x

Author Roseboom, Isaac G.
Pimbblet, Kevin A.
Drinkwater, Michael J.
Cannon, Russell D.
De Propris, Roberto
Edge, Alastair C.
Eisenstein, Daniel J.
Nichol, Robert C.
Wake, David A.
Bland-Hawthorn, Joss
Bridges, Terry J.
Carson, Daniel
Colless, Matthew
Couch, Warrick J.
Croom, S. M.
Driver, S. P.
Hewett, P. C.
Loveday, J.
Ross, N.
Schneider, D. P.
Shanks, T.
Sharp, R. G.
Weilbacher, P
Title The 2dF-SDSS LRG and QSO survey: the star formation histories of luminous red galaxies
Journal name Monthly Notices Of The Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
Publication date 2006-11
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2006.11024.x
Open Access Status DOI
Volume 373
Issue 1
Start page 349
End page 360
Total pages 12
Editor A. C. Fabian
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Collection year 2006
Language eng
Abstract We present a detailed investigation into the recent star formation histories of 5697 luminous red galaxies (LRGs) based on the H delta (4101 angstrom), and [O II] (3727 angstrom) lines and the D4000 index. LRGs are luminous (L > 3L*) galaxies which have been selected to have photometric properties consistent with an old, passively evolving stellar population. For this study, we utilize LRGs from the recently completed 2dF-SDSS LRG and QSO Survey (2SLAQ). Equivalent widths of the H delta and [O II] lines are measured and used to define three spectral types, those with only strong H delta absorption (k+a), those with strong [O II] in emission (em) and those with both (em+a). All other LRGs are considered to have passive star formation histories. The vast majority of LRGs are found to be passive (similar to 80 per cent); however, significant numbers of k+a (2.7 per cent), em+a (1.2 per cent) and em LRGs (8.6 per cent) are identified. An investigation into the redshift dependence of the fractions is also performed. A sample of SDSS MAIN galaxies with colours and luminosities consistent with the 2SLAQ LRGs is selected to provide a low-redshift comparison. While the em and em+a fractions are consistent with the low-redshift SDSS sample, the fraction of k+a LRGs is found to increase significantly with redshift. This result is interpreted as an indication of an increasing amount of recent star formation activity in LRGs with redshift. By considering the expected lifetime of the k+a phase, the number of LRGs which will undergo a k+a phase can be estimated. A crude comparison of this estimate with the predictions from semi-analytic models of galaxy formation shows that the predicted level of k+a and em+a activities is not sufficient to reconcile the predicted mass growth for massive early types in a hierarchical merging scenario.
Keyword surveys
galaxies : evolution
galaxies : formation
Digital Sky Survey
Color-magnitude Relation
Central Cluster Galaxies
Emission-line Spectra
Delta-strong Galaxies
Deep Deep Survey
Elliptic Galaxies
Distant Clusters
Field Galaxies
Redshift Survey
Q-Index Code C1
Additional Notes Authors of this document: Roseboom, IG; Pimbblet, KA; Drinkwater, MJ; Cannon, RD; De Propris, R; Edge, AC; Eisenstein, DJ; Nichol, RC; Smail, I; Wake, DA; Bland-Hawthorn, J; Bridges, TJ; Carson, D; Colless, M; Couch, WJ; Croom, SM; Driver, SP; Hewett, PC; Loveday, J; Ross, N; Schneider, DP; Shanks, T; Sharp, RG; Weilbacher, P. DOC: 10.1111/j.1365-2966.2006.11024.x

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Created: Wed, 15 Aug 2007, 09:48:01 EST