Conditional quenching: a detailed look at the SFR-density relation at z ∼ 0.9 from ORELSE
Abstract
We present a study of the star formation rate (SFR)-density relation at z ∼ 0.9 using data drawn from the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. We find that SFR does depend on environment, but only for intermediate-stellar mass galaxies (1010.1 < M*/M⊙ < 1010.8) wherein the median SFR at the highest densities is 0.2-0.3 dex less than at lower densities at a significance of 4σ. Galaxies that are more/less massive than this have SFRs that vary at most by {≈ }20{{ per cent}} across all environments, but show no statistically significant trend. We further split galaxies into low-redshift (z ∼ 0.8) and high-redshift (z ∼ 1.05) subsamples and observe nearly identical behaviour. We devise a simple toy model to explore possible star formation histories for galaxies evolving between these redshifts. The key assumption in this model is that star-forming galaxies in a given environment-stellar mass bin can be described as a superposition of two exponential time-scales (SFR ∝ e-t/τ): a long-τ time-scale with τ = 4 Gyr to simulate `normal' star-forming galaxies, and a short-τ time-scale with free τ (between 0.3 ≤ τ/Gyr ≤ 2) to simulate galaxies on a quenching trajectory. In general, we find that galaxies residing in low/high environmental densities are more heavily weighted to the long-τ/short-τ pathways, respectively, which we argue is a signature of environmental quenching. Furthermore, for intermediate-stellar mass galaxies this transition begins at intermediate-density environments suggesting that environmental quenching is relevant in group-like haloes and/or cluster infall regions.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2019
- DOI:
- 10.1093/mnras/stz342
- arXiv:
- arXiv:1812.04633
- Bibcode:
- 2019MNRAS.484.4695T
- Keywords:
-
- techniques: photometric;
- techniques: spectroscopic;
- galaxies: clusters: general;
- galaxies: evolution;
- galaxies: groups: general;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 17 pages, 7 figures