Bibcode
Fabrizio, M.; Bono, G.; Nonino, M.; Łokas, E. L.; Ferraro, I.; Iannicola, G.; Buonanno, R.; Cassisi, S.; Coppola, G.; Dall’Ora, M.; Gilmozzi, R.; Marconi, M.; Monelli, M.; Romaniello, M.; Stetson, P. B.; Thévenin, F.; Walker, A. R.
Bibliographical reference
The Astrophysical Journal, Volume 830, Issue 2, article id. 126, 17 pp. (2016).
Advertised on:
10
2016
Journal
Citations
26
Refereed citations
23
Description
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.