A New Look at the Kinematics of Neutral Hydrogen in the Small Magellanic Cloud

Details A New Look at the Kinematics of Neutral Hydrogen in the Small Magellanic Cloud A New Look at the Kinematics of Neutral Hydrogen in the Small Magellanic Cloud

2003-12-09

arxiv.org/abs/astro-ph/0312223v1

Astrophys.J. 604 (2004) 176-186

Astronomy and Astrophysics

Astrophysics

To appear in ApJ, March 20 2004, 11 figures

Scientific paper

10.1086/381869

We have used the latest HI observations of the Small Magellanic Cloud (SMC), obtained with the Australia Telescope Compact Array and the Parkes telescope, to re-examine the kinematics of this dwarf, irregular galaxy. A large velocity gradient is found in the HI velocity field with a significant symmetry in iso-velocity contours, suggestive of a differential rotation. A comparison of HI data with the predictions from tidal models for the SMC evolution suggests that the central region of the SMC corresponds to the central, disk- or bar-like, component left from the rotationally supported SMC disk prior to its last two encounters with the Large Magellanic Cloud. In this scenario, the velocity gradient is expected as a left-over from the original, pre-encounter, angular momentum. We have derived the HI rotation curve and the mass model for the SMC. This rotation curve rapidly rises to about 60 km/s up to the turnover radius of ~3 kpc. A stellar mass-to-light ratio of about unity is required to match the observed rotation curve, suggesting that a dark matter halo is not needed to explain the dynamics of the SMC. A set of derived kinematic parameters agrees well with the assumptions used in tidal theoretical models that led to a good reproduction of observational properties of the Magellanic System. The dynamical mass of the SMC, derived from the rotation curve, is 2.4x10^9 Msolar.

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