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The Carina Project. X. On the Kinematics of Old and Intermediate-age Stellar Populations1,2

Journal
Date Issued
2016
Author(s)
•
Bono, G.
•
•
Łokas, E. L.
•
Ferraro, I.
•
Iannicola, G.
•
Buonanno, R.
•
•
Coppola, G.
•
•
Gilmozzi, R.
•
•
Monelli, M.
•
Romaniello, M.
•
Stetson, P. B.
•
Thévenin, F.
•
Walker, A. R.
DOI
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.
Volume
830
Issue
2
Start page
126
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2016ApJ...830..126F
Rights
open.access
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