Three Dusty Star-forming Galaxies at z ∼ 1.5: Mergers and Disks on the Main Sequence

Abstract

Abstract The main sequence of galaxies, a correlation between the star formation rates (SFRs) and stellar masses of galaxies, has been observed out to z ∼ 4. Galaxies within the scatter of the correlation are typically interpreted to be secularly evolving while galaxies with SFRs elevated above the main sequence are interpreted to be undergoing interactions or to be Toomre-unstable disks with starbursting clumps. In this paper, we investigate the recent merger histories of three dusty star-forming galaxies, identified by their bright submillimeter emission at z ∼ 1.5. We analyze rest-frame optical and UV imaging, rest-frame optical emission line kinematics using slit spectra obtained with the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on Keck I, and calculate Gini and M 20 statistics for each galaxy and conclude two are merger driven while the third is an isolated disk galaxy. The disk galaxy lies ∼4× above the main sequence, one merger lies within the scatter of the main sequence, and one merger lies ∼4× below the main sequence. This hints that the location of a galaxy with respect to the main sequence may not be a useful discriminator of the recent star formation history of high-M galaxies at z ∼ 1.