STAR FORMATION AT 4 < z < 6 FROM THE SPITZER LARGE AREA SURVEY WITH HYPER-SUPRIME-CAM (SPLASH)

Using the first 50% of data collected for the Spitzer Large Area Survey with Hyper-Suprime-Cam observations on the 1.8 deg$^2$ Cosmological Evolution Survey we estimate the masses and star formation rates of 3398$M_*$ $>10^{10}$ $M_ \odot$ star-forming galaxies at 4 < $z$ < 6 with a substantial population up to $M_*$$\geq$10$^{11.5}$$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 similar to 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 $z$ similar to $6$ or else occurs rapidly, so that few galaxies are visible in transition between star-forming and quenched.