The Carina Project. X. On the Kinematics of Old and Intermediate-age Stellar Populations1,2
Abstract
We present new radial velocity (RV) measurements of old (horizontal branch) and intermediate-age (red clump) stellar tracers in the Carina dwarf spheroidal. They are based on more than 2200 low-resolution spectra collected with VIMOS at Very Large Telescope (VLT). The targets are faint (20 ≲ V ≲ 21.5 mag), but the accuracy at the faintest limit is ≤9 km s-1. These data were complemented with RV measurements either based on spectra collected with FORS2 and FLAMES/GIRAFFE at VLT or available in the literature. We ended up with a sample of 2748 stars and among them, 1389 are candidate Carina stars. We found that the intermediate-age stellar component shows a well-defined rotational pattern around the minor axis. The western and the eastern side of the galaxy differ by +5 and -4 km s-1 when compared with the main RV peak. The old stellar component is characterized by a larger RV dispersion and does not show evidence of the RV pattern. We compared the observed RV distribution with N-body simulations for a former disky dwarf galaxy orbiting a giant Milky Way-like galaxy. We rotated the simulated galaxy by 60° with respect to the major axis, we kept the observer on the orbital plane of the dwarf and extracted a sample of stars similar to the observed one. Observed and predicted {V}{rot}/σ ratios across the central regions are in remarkable agreement. This evidence indicates that Carina was a disky dwarf galaxy that experienced several strong tidal interactions with the Milky Way. Owing to these interactions, Carina transformed from a disky to a prolate spheroid and the rotational velocity transformed into random motions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2016
- DOI:
- 10.3847/0004-637X/830/2/126
- arXiv:
- arXiv:1607.03181
- Bibcode:
- 2016ApJ...830..126F
- Keywords:
-
- galaxies: dwarf;
- galaxies: individual: Carina;
- galaxies: kinematics and dynamics;
- galaxies: stellar content;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 21 pages, 16 figures, 4 tables. Accepted for publication in ApJ