Effects of Local Environment and Stellar Mass on Galaxy Quenching out to z~3

We study the effects of local environment and stellar mass on galaxy properties using a mass complete sample of quiescent and star-forming systems in the COSMOS field at $z\lesssim$ 3. We show that at $z\lesssim$ 1, the median star-formation rate (SFR) and specific SFR (sSFR) of all galaxies depend on environment, but they become independent of environment at $z\gtrsim$ 1. However, we find that only for \textit{star-forming} galaxies, the median SFR and sSFR are similar in different environments, regardless of redshift and stellar mass. We find that the quiescent fraction depends on environment at $z\lesssim$ 1, and on stellar mass out to $z\sim$ 3. We show that at $z\lesssim$ 1, galaxies become quiescent faster in denser environments and that the overall environmental quenching efficiency increases with cosmic time. Environmental and mass quenching processes depend on each other. At $z\lesssim$ 1, denser environments more efficiently quench galaxies with higher masses (log($M/M_{\odot}$)$\gtrsim$ 10.7), possibly due to a higher merger rate of massive galaxies in denser environments, and that mass quenching is more efficient in denser regions. We show that the overall mass quenching efficiency ($\epsilon_{mass}$) for more massive galaxies (log($M/M_{\odot}$)$\gtrsim$ 10.2) rises with cosmic time until $z\sim$ 1 and flattens out since then. However, for less massive galaxies, the rise in $\epsilon_{mass}$ continues to the present time. Our results suggest that environmental quenching is only relevant at $z\lesssim$ 1, likely a fast process, whereas mass quenching is the dominant mechanism at $z\gtrsim$ 1, with a possible stellar feedback physics.

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