The Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS): the Evolution of Dusty and Non-Dusty Galaxies with Stellar Mass at z=2-6

Abstract: The Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS) has obtained the largest ultra-deep Spitzer maps to date in a single field of the sky. We considered the sample of about 66,000 SMUVS sources at $z=2-6$ to investigate the evolution of dusty and non-dusty galaxies with stellar mass through the analysis of the galaxy stellar mass function (GSMF). We further divide our non-dusty galaxy sample with rest-frame optical colours to isolate red quiescent (`passive') galaxies. At each redshift, we identify a characteristic stellar mass in the GSMF above which dusty galaxies dominate, or are at least as important as non-dusty galaxies. Below that stellar mass, non-dusty galaxies comprise about 80% of all sources, at all redshifts except at $z=4-5$. The percentage of dusty galaxies at $z=4-5$ is unusually high: 30-40% for $M_{}=10^9 - 10^{10.5} \, \rm M_\odot$ and $>80\%$ at $M_>10^{11} \, \rm M_\odot$, which indicates that dust obscuration is of major importance in this cosmic period. The overall percentage of massive ($\log_{10} (M_/M_\odot)>10.6$) galaxies that are quiescent increases with decreasing redshift, reaching $>30\%$ at $z\sim2$. Instead, the quiescent percentage among intermediate-mass galaxies (with $\log_{10} (M_/M_\odot)=9.7-10.6$) stays roughly constant at a $\sim 10\%$ level. Our results indicate that massive and intermediate-mass galaxies clearly have different evolutionary paths in the young Universe, and are consistent with the scenario of galaxy downsizing.