THE MOSDEF SURVEY: DYNAMICAL AND BARYONIC MASSES AND KINEMATIC STRUCTURES OF STAR-FORMING GALAXIES AT 1.4 ≤ z ≤ 2.6

Abstract

ABSTRACT We present H &agr; ?> gas kinematics for 178 star-forming galaxies at z ∼ 2 ?> from the MOSFIRE Deep Evolution Field survey. We have developed models to interpret the kinematic measurements from fixed-angle multi-object spectroscopy, using structural parameters derived from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey Hubble Space Telescope/F160W imaging. For 35 galaxies, we measure resolved rotation with a median of ( V / &sgr; V , 0 ) R E = 2.1 ?> . We derive dynamical masses from the kinematics and sizes and compare them to baryonic masses, with gas masses estimated from dust-corrected H &agr; ?> star formation rates (SFRs) and the Kennicutt–Schmidt relation. When assuming that galaxies with and without observed rotation have the same median ( V / &sgr; V , 0 ) R E ?> , we find good agreement between the dynamical and baryonic masses, with a scatter of &sgr; rms = 0.34 dex ?> and a median offset of Δ log 10 M = 0.04 dex ?> . This comparison implies a low dark matter fraction (8% within an effective radius) for a Chabrier initial mass function (IMF), and disfavors a Salpeter IMF. Moreover, the requirement that M dyn ?> / M baryon ?> should be independent of inclination yields a median value of ( V / &sgr; V , 0 ) R E = 2.1 ?> for galaxies without observed rotation. If, instead, we treat the galaxies without detected rotation as early-type galaxies, the masses are also in reasonable agreement ( Δ log 10 M = − 0.07 dex ?> , &sgr; rms = 0.37 dex ?> ). The inclusion of gas masses is critical in this comparison; if gas masses are excluded, there is an increasing trend of M dyn ?> / M * ?> with higher specific SFR (SSFR). Furthermore, we find indications that V / &sgr; ?> decreases with increasing H &agr; ?> SSFR for our full sample, which may reflect disk settling. We also study the Tully–Fisher relation and find that at fixed stellar mass S 0.5 = ( 0.5 V 2.2 2 + &sgr; V , 0 2 ) 1 / 2 ?> was higher at earlier times. At fixed baryonic mass, we observe the opposite trend. Finally, the baryonic and dynamical masses of the active galactic nuclei in our sample are also in excellent agreement, suggesting that the kinematics trace the host galaxies.