Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/42735

Title

Selection and photometric properties of K+A galaxies

Author(s)

Quintero, Alejandro D.;  Hogg, David W.;  Blanton, Michael R.;  Schlegel, David J.;  Eisenstein, Daniel J.;  Gunn, James E.;  Brinkmann, Jon;  Fukugita, Masataka;  Glazebrook, Karl;  Goto, Tomotsugu

Abstract

Two different simple measurements of galaxy star formation rate with different timescales are compared empirically on 156,395 fiber spectra of galaxies with r < 17.77 mag taken from the Sloan Digital Sky Survey in the redshift range 0.05 < z < 0.20: a ratio A/K found by fitting a linear sum of an average old stellar population spectrum (K) and average A star spectrum (A) to the galaxy spectrum, and the equivalent width (EW) of the Hα emission line. The two measures are strongly correlated, but there is a small, clearly separated population of outliers from the median correlation that display excess A/K relative to Hα EW. These "K+A" (or "E+A") galaxies must have dramatically decreased their star formation rates over the last ∼1 Gyr. The K+A luminosity distribution is similar to that of the total galaxy population. The K+A population appears to be bulge-dominated, but bluer and with higher surface brightness than normal bulge-dominated galaxies; it appears that K+A galaxies will fade with time into normal bulge-dominated galaxies. The inferred rate density for K+A galaxy formation is ∼10-4 h3 Mpc-3 Gyr -1 at redshift z ∼ 0.1. These events are taking place in the field; the K+A galaxies found in this study do not primarily lie in the high-density environments or clusters typical of bulge-dominated populations.

Publication type

Journal article

Source

Astrophysical Journal, Vol. 602, no. 1 (Feb 2004), pp. 190-199

Publication year

2004

Keyword(s)

Clusters;  Digital sky survey;  Disk galaxies;  Distant clusters;  E+A-galaxies;  Evolution;  Fundamental parameters;  Galaxies;  History;  Luminosity function;  Spectroscopic target selection;  Star-formation;  Statistics;  Stellar galaxies;  Solar neighbourhood

Publisher

University of Chicago

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1086/380601

Copyright

Copyright © 2004 The American Astronomical Society. All rights reserved.

Peer reviewed