The kinematics of massive high-redshift dusty star-forming galaxies

Abstract

We present a new method for modelling the kinematics of galaxies from interferometric observations by performing the optimization of the kinematic model parameters directly in visibility-space instead of the conventional approach of fitting velocity fields produced with the CLEAN algorithm in real-space. We demonstrate our method on ALMA observations of ${}^{12}$CO (2$-$1), (3$-$2) or (4$-$3) emission lines from an initial sample of 30 massive 850$\hat{I}¼$m-selected dusty star-forming galaxies with far-infrared luminosities $\gtrsim$$10^{12}$L${}_{\odot }$ in the redshift range $z\sim$1.2$-$4.7. Using the results from our modelling analysis for the 12 sources with the highest signal-to-noise emission lines and disk-like kinematics, we conclude the following: (i) Our sample prefers a CO-to-$H_2$ conversion factor, of $\hat{I}{\pm }_{\mathrm{CO}}=0.92\pm 0.36$; (ii) These far-infrared luminous galaxies follow a similar Tully$-$Fisher relation between the circularized velocity, $V_{\mathrm{circ}}$, and baryonic mass, $M_{\mathrm{b}}$, as more typical star-forming samples at high redshift, but extend this relation to much higher masses $-$ showing that these are some of the most massive disk-like galaxies in the Universe; (iii) Finally, we demonstrate support for an evolutionary link between massive high-redshift dusty star-forming galaxies and the formation of local early-type galaxies using the both the distributions of the baryonic and kinematic masses of these two populations on the $M_{\mathrm{b}}-\ddot{I}ƒ$ plane and their relative space densities.