Letter to the Editor

Integrated specific star formation rates of galaxies, groups, and clusters: a continuous upper limit with stellar mass?

¹ Universitäts–Sternwarte München, Scheinerstraße 1, 81679 München, Germany e-mail: feulner@usm.lmu.de
² Max–Planck–Institut für extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
³ University of Auckland, Private Bag 92019, Morrin Road, Glen Innes, Auckland, New Zealand
⁴ University of Canterbury, Private Bag 4800, Christchurch, New Zealand

Received: 24 February 2006
Accepted: 22 March 2006

Abstract

Aims.We investigate the build-up of stellar mass through star formation in field galaxies, galaxy groups, and clusters in order to better understand the physical processes regulating star formation in different haloes.

Methods.In order to do so we relate ongoing star formation activity to the stellar mass by studying the integrated specific star formation rate (SSFR), defined as the star-formation rate per unit stellar mass, as a function of integrated stellar mass for samples of field galaxies, groups of galaxies, and galaxy clusters at . The star formation rate (SFR) is derived from the ultraviolet continuum for the galaxies and group members, and from emission line fluxes for the cluster galaxies. The stellar masses are computed from multi-band photometry including the near-infrared bands for the galaxies and groups, and from the dynamical mass for the cluster sample.

Results.For the first time, integrated SSFRs for clusters and groups are presented and related to the SSFRs of field galaxies. Tentatively, we find a continuous upper limit for galaxies, groups, and clusters in the SSFR-stellar mass plane over seven orders of magnitude in stellar mass. This might indicate that the physical processes which control star formation in dark matter haloes of different mass have the same scaling with mass over a wide range of masses from dwarf galaxies to massive clusters of galaxies.