STAR FORMATION AT 4 &lt; <i>z</i> &lt; 6 FROM THE <i>SPITZER</i> LARGE AREA SURVEY WITH HYPER-SUPRIME-CAM (SPLASH)

Abstract

Using the first 50% of data collected for the Spitzer Large Area Survey with\nHyper-Suprime-Cam (SPLASH) observations on the 1.8 deg$^2$ Cosmological\nEvolution Survey (COSMOS) we estimate the masses and star formation rates of\n3398 $M_*&gt;10^{10}M_\\odot $ star-forming galaxies at $4 &lt; z &lt; 6$ with a\nsubstantial population up to $M_* \\gtrsim 10^{11.5} M_\\odot$. We find that the\nstrong correlation between stellar mass and star formation rate seen at lower\nredshift (the "main sequence" of star-forming galaxies) extends to $z\\sim6$.\nThe observed relation and scatter is consistent with a continued increase in\nstar formation rate at fixed mass in line with extrapolations from\nlower-redshift observations. It is difficult to explain this continued\ncorrelation, especially for the most massive systems, unless the most massive\ngalaxies are forming stars near their Eddington-limited rate from their first\ncollapse. Furthermore, we find no evidence for moderate quenching at higher\nmasses, indicating quenching either has not occurred prior to $z \\sim 6$ or\nelse occurs rapidly, so that few galaxies are visible in transition between\nstar-forming and quenched.\n