Kinematics of massive stars in the Small Magellanic Cloud

Christopher J. Evans (1), Ian D. Howarth (2)

(1) UK Astronomy Technology Centre, Edinburgh; (2) University College London

We present radial velocities for 2045 stars in the Small Magellanic Cloud (SMC), obtained from the 2dF survey by Evans et al. (2004). The great majority of these stars are of OBA type, tracing the dynamics of the young stellar population. Dividing the sample into ad hoc `bar' and `wing' samples (north and south, respectively, of the line: $delta = -77^{circ}50^{prime} + [4alpha]^{prime}$, where $alpha$ is in minutes of time) we find that the velocities in the SMC bar show a gradient of 26.3 +/- 1.6 km/s/deg at a position angle of 126 +/- 4 deg. The derived gradient in the bar is robust to the adopted line of demarcation between the two samples. The largest redshifts are found in the SMC wing, in which the velocity distribution appears distinct from that in the bar, most likely a consequence of the interaction between the Magellanic Clouds that is
predicted to have occurred 0.2 Gyr ago. The mean velocity for all stars in the sample is +172.0 +/- 0.2 km/s (redshifted by ~20 km/s when compared to published results for older
populations), with a velocity dispersion of 30 km/s.

Reference: MNRAS
Status: Manuscript has been accepted