On the Radial Velocity Distribution of the Carina dSph galaxy

¹ Univ. ToV, via della Ricerca Scientifica 1, 00133 Rome, Italy
² INAF–OAT, via G.B. Tiepolo 11, 40131 Trieste, Italy
³ DAO–HIA, NRC, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
⁴ INAF–OAR, via Frascati 33, Monte Porzio Catone, Rome, Italy
⁵ ASI–Science Data Center, ASDC c/o ESRIN, via G. Galilei, 00044 Frascati, Italy
⁶ IAC, Calle via Lactea, 38200 La Laguna, Tenerife, Spain
⁷ NOAO–CTIO, Casilla 603, La Serena, Chile

e-mail: fabrizio@roma2.infn.it

Abstract

We present the radial velocity (RV) distribution of Carina dSph, obtained using low-, medium- and high-resolution spectroscopic data collected with FORS2 and GIRAFFE at the VLT. We found that regions where the mean RV is smaller the dispersion is also smaller, and the RV distribution is sharper (i.e. the kurtosis attains larger values). The mean RV, when moving to lower Galactic latitude, decreases by ∼ 5kms⁻¹, attains a well defined minimum outside the galaxy center, and a constant value at larger distances. The RV gradient appears to be in the direction of the Carina proper motion. However, this parameter is affected by large uncertainties to reach a firm conclusion. These findings are probably reminiscent of a substructure with transition properties, already detected in dwarf ellipticals, and call for independent confirmations.