THE DEPENDENCE OF STAR FORMATION RATES ON STELLAR MASS AND ENVIRONMENT AT z ∼ 0.8

Abstract

We examine the star formation rates (SFRs) of galaxies in a redshift slice encompassing the z = 0.834 cluster RX J0152.7-1357. We used a low-dispersion prism in the Inamori Magellan Areal Camera and Spectrograph (IMACS) to identify galaxies with z AB < 23.3 mag in diverse environments around the cluster out to projected distances of ∼ 8 Mpc from the cluster center. We utilize a mass-limited sample (M > 2 × 10 10 M ⊙ ) of 330 galaxies that were imaged by Spitzer MIPS at 24 µm to derive SFRs and study the dependence of specific SFR (SSFR) on stellar mass and environment. We find that the SFR and SSFR show a strong decrease with increasing local density, similar to the relation at z ∼ 0. Our result contrasts with other work at z ∼ 1 that find the SFR-density trend to reverse for luminosity-limited samples. These other results appear to be driven by star-formation in lower mass systems (M ∼ 10 10 M ⊙ ). Our results imply that the processes that shut down star-formation are present in groups and other dense regions in the field. Our data also suggest that the lower SFRs of galaxies in higher density environments may reflect a change in the ratio of star-forming to non-starforming galaxies, rather than a change in SFRs. As a consequence, the SFRs of star-forming galaxies, in environments ranging from small groups to clusters, appear to be similar and largely unaffected by the local processes that truncate star-formation at z ∼ 0.8.

Discovery of the X-ray selected galaxy cluster XMMU J0338.8+0021 atz= 1.49

“…The situation is different in clusters found so far at z < 1.4, where active star-forming galaxies preferentially reside in the cluster outskirts (e.g. Balogh et al 2004;Lidman et al 2008;Patel et al 2009). However, it is expected that more distant galaxy clusters contain a larger number of star-forming galaxies in their central regions (e.g.…”

GOODS-Herschel: the impact of galaxy-galaxy interactions on the far-infrared properties of galaxies

“…In the high-z universe, some studies found similar results (e.g., Patel et al 2009;Feruglio et al 2010), but there are also hints for an opposite trend (i.e. increasing SFRs or star-forming galaxy fractions with increasing the background density) known as the reversal of SFR-density relation (e.g., Elbaz et al 2007;Popesso et al 2011a,b).…”

Environmental dependence of local luminous infrared galaxies

“…The SFR in their study is the "median" SFR in a given mass bin, which is different from the spatially "averaged" SFR of the nearby galaxies in Elbaz et al (2007) and Cooper et al (2008). Patel et al (2009) argue that the contradictory results may be caused by the different environment that they investigate and by the different sample selection. They observed the central region of galaxy clusters (that is not well resolved by the other studies).…”

“…For example, Elbaz et al (2007) used the GOODS data and find that the SFR-density relation observed locally is reversed at z ∼ 1, in the sense that the "average" SFR of galaxies over a given volume increases with the local galaxy density (see also Cooper et al 2008;Ideue et al 2009;Tran et al 2010). In contrast, Patel et al (2009) observed the galaxies in a galaxy cluster (RX J0152.7−1357) at z = 0.834 and find that the SFR-density relation at that redshift is not similar to those in Elbaz et al (2007) and Cooper et al (2008), but is similar to the one in the local universe (see also Feruglio et al 2010). The SFR in their study is the "median" SFR in a given mass bin, which is different from the spatially "averaged" SFR of the nearby galaxies in Elbaz et al (2007) and Cooper et al (2008).…”