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K+a galaxies in the zCOSMOS survey: Physical properties of systems in their post-starburst phase

Vergani, D. and Zamorani, G. and Lilly, S. and Lamareille, F. and Halliday, C. and Scodeggio, M. and Vignali, C. and Ciliegi, P. and Bolzonella, M. and Bondi, M. and Kovač, K. and Knobel, C. and Zucca, E. and Caputi, K. and Pozzetti, L. and Bardelli, S. and Mignoli, M. and Iovino, A. and Carollo, C. M. and Contini, T. and Kneib, J.-P. and Le Fèvre, O. and Mainieri, V. and Renzini, A. and Bongiorno, A. and Coppa, G. and Cucciati, O. and de la Torre, S. and de Ravel, L. and Franzetti, P. and Garilli, B. and Kampczyk, P. and Le Borgne, J.-F. and Le Brun, V. and Maier, C. and Pello , R. and Peng, Y. and Perez Montero, E. and Ricciardelli, E. and Silverman, J. D. and Tanaka, M. and Tasca, L. and Tresse, L. and Abbas, U. and Bottini, D. and Cappi, A. and Cassata, P. and Cimatti, A. and Guzzo, L. and Koekemoer, A. M. and Leauthaud, A. and Maccagni, D. and Marinoni, C. and McCracken, H. J. and Memeo, P. and Meneux, B. and Oesch, P. and Porciani, C. and Scaramella, R. and Capak, P. and Sanders, D. and Scoville, N. and Taniguchi, Y. (2010) K+a galaxies in the zCOSMOS survey: Physical properties of systems in their post-starburst phase. Astronomy and Astrophysics, 509 . A42. ISSN 0004-6361.

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Aims. The identities of the main processes triggering and quenching star-formation in galaxies remain unclear. A key stage in evolution, however, appears to be represented by post-starburst galaxies. To investigate the prevalence of these galaxies and their impact on galaxy evolution in general, we initiated a multiwavelength study of galaxies with k+a spectral features in the well-studied COSMOS field. Methods. We examine a mass-selected sample of k+a galaxies in the COSMOS field at z = 0.48-1.2 using the spectroscopic zCOSMOS sample. To classify galaxies in their k+a phase, we use a spectroscopic criterion, based on the amplitude of the Hδ absorption line and the absence of the [OII] emission line. We develop our analysis for a well-defined sample by imposing stringent confidence levels on the spectroscopic redshifts and spectral measurements. We compare our results for two mass-selected samples of star-forming and quiescent galaxies selected using a purely spectral classification scheme from the 10 000 zCOSMOS catalogue (i.e. , based on measurements of 4000 Å break and EW[OII]). Results. In our mass-limited sample, k+a galaxies occupy the brightest tail of the luminosity distribution. They are as massive as quiescent galaxies and populate the green valley in the colour versus luminosity (or stellar mass) distribution. A small percentage (<8%) of these galaxies have radio and/or X-ray counterparts (implying an upper limit to the SFR of ~8 M_☉  yr^(-1)). Over the entire redshift range explored, the class of post-starburst galaxies is morphologically a heterogeneous population with a similar incidence of bulge-dominated and disky galaxies. This distribution does not vary with the strength of the Hδ absorption line but instead with stellar mass in a way reminiscent of the well-known mass-morphology relation. The results about the incidence of asymmetries and the concentration of the light distribution derived from HST/ACS images imply that this galaxy population possibly represents an intermediate stage of galaxy evolution. Although k+a galaxies are also found in underdense regions, they appear to reside typically in a similarly rich environment as quiescent galaxies on a physical scale of ~2–8 Mpc, and in groups they show a morphological early-to-late type ratio similar to the quiescent galaxy class. With the current data set, we do not find evidence of statistical significant evolution in either the number/mass density of k+a galaxies at intermediate redshift with respect to the local values, or the spectral properties, although more solid results on this and other aspects will be obtained following the completion of the survey. Conclusions. Several mechanisms related and unrelated to the environment are at work in quenching star-formation activity in galaxies on short timescales (<1 Gyr). Those galaxies, which are affected by a sudden quenching of their star-formation activity, may increase the stellar mass of the red-sequence by up to a non-negligible level of ~10%.

Item Type:Article
Related URLs:
URLURL TypeDescription
McCracken, H. J.0000-0002-9489-7765
Scoville, N.0000-0002-0438-3323
Additional Information:© 2010 ESO. Received: 30 June 2009; accepted: 9 September 2009. This work has been supported in part by the grant ASI/COFIS/WP3110 I/026/07/0. We thank the referee for providing constructive comments.
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)ASI/COFIS/WP3110 I/026/07/0
Subject Keywords:galaxies: evolution; galaxies: fundamental parameters; galaxies: luminosity function, mass function; cosmology: observations; galaxies: formation
Record Number:CaltechAUTHORS:20100224-111937242
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Official Citation:K+a galaxies in the zCOSMOS survey - Physical properties of systems in their post-starburst phase D. Vergani, G. Zamorani, S. Lilly, F. Lamareille, C. Halliday, M. Scodeggio, C. Vignali, P. Ciliegi, M. Bolzonella, M. Bondi, K. Kova, C. Knobel, E. Zucca, K. Caputi, L. Pozzetti, S. Bardelli, M. Mignoli, A. Iovino, C. M. Carollo, T. Contini, J.-P. Kneib, O. Le Fèvre, V. Mainieri, A. Renzini, A. Bongiorno, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, P. Franzetti, B. Garilli, P. Kampczyk, J.-F. Le Borgne, V. Le Brun, C. Maier, R. Pello, Y. Peng, E. Perez Montero, E. Ricciardelli, J. D. Silverman, M. Tanaka, L. Tasca, L. Tresse, U. Abbas, D. Bottini, A. Cappi, P. Cassata, A. Cimatti, L. Guzzo, A. M. Koekemoer, A. Leauthaud, D. Maccagni, C. Marinoni, H. J. McCracken, P. Memeo, B. Meneux, P. Oesch, C. Porciani, R. Scaramella, P. Capak, D. Sanders, N. Scoville and Y. Taniguchi A&A 509 A42 (2010) DOI: 10.1051/0004-6361/200912802
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17577
Deposited By: Jason Perez
Deposited On:24 Feb 2010 21:24
Last Modified:19 May 2017 18:42

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