ALMA sub-/millimeter sources among $Spitzer$ SMUVS galaxies at $z>2$ in the COSMOS field

Abstract

Sub-millimeter observations reveal the star-formation activity obscured by dust in the young Universe. It still remains unclear how galaxies detected at sub-millimeter wavelengths are related to ultraviolet/optical-selected galaxies in terms of their observed quantities, physical properties, and evolutionary stages. Deep near- and mid-infrared observational data are crucial to characterize the stellar properties of galaxies detected with sub-millimeter emission. In this study, we make use of a galaxy catalog from the $Spitzer$ Matching Survey of the UltraVISTA ultra-deep Stripes. By cross-matching with a sub-millimeter source catalog constructed with the archival data of the Atacama Large Millimeter/submillimeter Array (ALMA), we search for galaxies at $z>$ 2 with a sub-millimeter detection in our galaxy catalog. We find that the ALMA-detected galaxies at $z>$ 2 are systematically massive and have redder $K_s$-[4.5] colors than the non-detected galaxies. The redder colors are consistent with the larger dust reddening values of the ALMA-detected galaxies obtained from SED fitting. We also find that the ALMA-detected galaxies tend to have brighter 4.5 $\mu$m magnitudes. This may suggest that they tend to have smaller mass-to-light ratios, and thus, to be younger than star-forming galaxies fainter at sub-millimeter wavelengths with similar stellar masses. We identify starburst galaxies with high specific star-formation rates among both ALMA-detected and non-detected SMUVS sources. Irrespective of their brightness at sub-millimeter wavelengths, these populations have similar dust reddening values, which may suggest a variety of dust SED shapes among the starburst galaxies at $z>2$.

14 pages, 7 figures, 2 tables, Accepted for publication in ApJ