We present a study of the star-formation rate ( SFR ) -density relation at z \sim 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 ( 10 ^ { 10.1 } < M _ { * } / M _ { \odot } < 10 ^ { 10.8 } ) wherein the median SFR at the highest densities is 0.2 - 0.3 dex less than at lower densities at a significance of 4 \sigma .
Interestingly , mass does not drive SFR ; galaxies that are more/less massive have SFRs that vary at most by \approx 20 \% across all environments showing no statistically significant dependence .
We further split galaxies into low-redshift ( z \sim 0.8 ) and high-redshift ( z \sim 1.05 ) subsamples and observe nearly identical behavior .
We devise a simple toy model to explore possible star-formation histories ( SFHs ) 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 timescales ( { SFR } \propto e ^ { - t / \tau } ) : a long - \tau timescale with \tau = 4 Gyr to simulate ‘ ‘ normal ’ ’ star-forming galaxies , and a short - \tau timescale with free \tau ( between 0.3 \leq \tau / { Gyr } \leq 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 - \tau /short - \tau 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 halos and/or cluster infall regions .