ALMA Millimeter/Submillimeter Sources among Spitzer SMUVS Galaxies at z > 2 in the COSMOS Field

Abstract

Submillimeter observations reveal the star formation activity obscured by dust in the young Universe. It still remains unclear how galaxies detected at submillimeter 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 submillimeter emission. In this study, we make use of a galaxy catalog from the Spitzer Matching survey of the UltraVISTA ultra-deep Stripes. By crossmatching with a submillimeter source catalog constructed with archival data of the Atacama Large Millimeter/submillimeter Array (ALMA), we search for galaxies at z > 2 with a submillimeter 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 nondetected galaxies. The redder colors are consistent with the larger dust reddening values of the ALMA-detected galaxies obtained from spectral energy distribution (SED) fitting. We also find that the ALMA-detected galaxies tend to have brighter 4.5 μm 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 submillimeter wavelengths with similar stellar masses. We identify starburst galaxies with high specific star formation rates among both ALMA-detected and nondetected SMUVS sources. Irrespective of their brightness at submillimeter wavelengths, these populations have similar dust reddening values, which may suggest a variety of dust SED shapes among the starburst galaxies at z > 2.