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 $M_{\ast }=10^9-10^{10.5}{\mathrm{M}}_{\odot }$ and $>80\%$ at $M_{\ast }>10^{11}{\mathrm{M}}_{\odot }$, which indicates that dust obscuration is of major importance in this cosmic period. The overall percentage of massive (${\log }_{10}(M_{\ast }/M_{\odot })>10.6$) galaxies that are quiescent increases with decreasing redshift, reaching $>30\%$ at $z\sim 2$. Instead, the quiescent percentage among intermediate-mass galaxies (with ${\log }_{10}(M_{\ast }/M_{\odot })=9.7-10.6$) 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.

Final version accepted for publication at the ApJ. Several test results and corresponding figures added. No conclusions changed. 27 pages, 20 figures