Star Formation at $4<z<6$ From the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH)

Abstract

Using the first 50% of data collected for the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH) observations on the 1.8 deg${}^2$ Cosmological Evolution Survey (COSMOS) we estimate the masses and star formation rates of 3398 $M_{\ast }>10^{10}{M}_{\odot }$ star-forming galaxies at $4<z<6$ with a substantial population up to $M_{\ast }\gtrsim 10^{11.5}{M}_{\odot }$. We find that the strong correlation between stellar mass and star formation rate seen at lower redshift (the "main sequence" of star-forming galaxies) extends to $z\sim 6$. The observed relation and scatter is consistent with a continued increase in star formation rate at fixed mass in line with extrapolations from lower-redshift observations. It is difficult to explain this continued correlation, especially for the most massive systems, unless the most massive galaxies are forming stars near their Eddington-limited rate from their first collapse. Furthermore, we find no evidence for moderate quenching at higher masses, indicating quenching either has not occurred prior to $z\sim 6$ or else occurs rapidly, so that few galaxies are visible in transition between star-forming and quenched.

ApJL, accepted