Abstract
We present the first detailed assessment of the large-scale rotation of any galaxy based on full three-dimensional velocity measurements. We do this for the LMC by combining our HST average proper motion (PM) measurements for stars in 22 fields, with existing line-of-sight (LOS) velocity measurements for 6790 individual stars. We interpret these data with a model of circular rotation in a flat disk. The PM and LOS data paint a consistent picture of the LMC rotation and their combination yields several new insights. The PM data imply a stellar dynamical center that coincides with the HI dynamical center, and a rotation curve amplitude consistent with that inferred from LOS velocity studies. The implied disk viewing angles agree with the range of values found in the literature, but continue to indicate variations with stellar population and/or radius. Young (RSG) stars rotate faster than old (RGB/AGB) stars due to asymmetric drift. Outside the central region, the circular velocity is approximately flat at Vcirc = 91.7 +/- 18.8 km/s. This is consistent with the baryonic Tully-Fisher relation, and implies an enclosed mass M(8.7 kpc) = (1.7 +/- 0.7) x 10^10 solar masses. The virial mass is larger and depends on the full extent of the dark halo. The tidal radius is 22.3 +/- 5.2 kpc (24.0 +/- 5.6 degrees). Combination of the PM and LOS data yields kinematic distance estimates for the LMC, but these are not yet competitive with other methods.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
