Kinematic analysis of the super-extended HI disk of the nearby spiral galaxy M 83

Abstract

We present new Hâ ¯I observations of the nearby massive spiral galaxy Mâ 83 taken with the JVLA at 21â ³ angular resolution (â 500 pc) of an extended (?1.5 deg2) ten-point mosaic combined with GBT single-dish data. We study the super-extended Hâ ¯I disk of M 83 (?50 kpc in radius), in particular disk kinematics, rotation, and the turbulent nature of the atomic interstellar medium. We define distinct regions in the outer disk (rgal> central optical disk), including a ring, a southern area, a southern arm and a northern arm. We examine Hâ ¯I gas surface density, velocity dispersion, and noncircular motions in the outskirts, which we compare to the inner optical disk. We find an increase of velocity dispersion (Ï v) toward the pronounced Hâ ¯I ring, indicative of more turbulent Hâ ¯I gas. Additionally, we report over a large galactocentric radius range (until rgal? 50 kpc) where Ï v is slightly larger than thermal component (i.e., > 8 km s1). We find that a higher star-formation rate (as traced by far UV emission) is not necessarily always associated with a higher Hâ ¯I velocity dispersion, suggesting that radial transport could be a dominant driver for the enhanced velocity dispersion. Furthermore, we find a possible branch that connects the extended Hâ ¯I disk to the dwarf irregular galaxy UGCA 365 and that deviates from the general direction of the northern arm. Lastly, we compare mass flow rate profiles (based on 2D and 3D tilted ring models) and find evidence for outflowing gas at rgal ? 2 kpc, inflowing gas at rgal ? 5.5 kpc, and outflowing gas at rgal? 14 kpc. We caution that mass flow rates are highly sensitive to the assumed kinematic disk parameters, in particular to inclination. Show more