The Kinematics of the Small Magellanic Cloud from Its Field Carbon Stars
Abstract
We present the first results of a velocity survey of the field population of carbon stars in the SMC. A total of 150 stars were observed spectroscopically in the near IR with an individual precision of +/- 1.8 km s^-1^. The carbon star population does not behave kinematically like the extreme Population I of the SMC: there is no evidence of a velocity splitting, in contradiction with the two-galaxy model of Mathewson, Ford, and Visvanathan, nor is there any evidence of rotation of the main body. In this respect carbon stars behave kinematically like the planetary nebulae system with which they share a velocity dispersion of ~27 km s^-1^. Carbon stars also exhibit the same velocity dispersion as a sample of halo metal-poor giants near NGC 121. The possibility exists that carbon stars and planetary nebulae belong to a spheroidal-like system, but this is uncertain for carbon stars due to lack of better spatial coverage. There are indications of streaming motions in the wing section between the SMC and the LMC with a positive gradient of 165 +/- 53 km s^-1^ degree^-1^ toward the LMC. The mass of the SMC as inferred from its velocity dispersion is near 10^9^ M_sun_ giving a visual mass-to-light ratio near 2. The heliocentric velocity of the SMC bar is 148.3 +/- 2.4 km s^-1^ (s.e.) corresponding to a galactocentric velocity of - 11.3 km s^-1^.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1989
- DOI:
- 10.1086/167790
- Bibcode:
- 1989ApJ...344..210H
- Keywords:
-
- Carbon Stars;
- Kinematics;
- Magellanic Clouds;
- Charge Coupled Devices;
- Mass To Light Ratios;
- Planetary Nebulae;
- Radial Velocity;
- Star Distribution;
- Astrophysics;
- GALAXIES: INTERNAL MOTIONS;
- GALAXIES: MAGELLANIC CLOUDS;
- GALAXIES: STRUCTURE;
- NEBULAE: PLANETARY;
- STARS: CARBON