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

FABRIZIO, MicheleMicheleFABRIZIOBono, G.G.BonoNONINO, MarioMarioNONINOŁokas, E. L.E. L.ŁokasFerraro, I.I.FerraroIannicola, G.G.IannicolaBuonanno, R.R.BuonannoCASSISI, SantiSantiCASSISICoppola, G.G.CoppolaDALL'ORA, MassimoMassimoDALL'ORAGilmozzi, R.R.GilmozziMARCONI, MarcellaMarcellaMARCONIMonelli, M.M.MonelliRomaniello, M.M.RomanielloStetson, P. B.P. B.StetsonThévenin, F.F.ThéveninWalker, A. R.A. R.Walker2020-05-212020-05-2120160004-637Xhttp://hdl.handle.net/20.500.12386/25048We 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.STAMPAenThe Carina Project. X. On the Kinematics of Old and Intermediate-age Stellar Populations1,2Article10.3847/0004-637X/830/2/1262-s2.0-85053361444000386488200029https://iopscience.iop.org/article/10.3847/0004-637X/830/2/1262016ApJ...830..126FFIS/05 - ASTRONOMIA E ASTROFISICA