The Carina Project. X. On the kinematics of old and intermediate-age stellar populations

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 2,200 low-resolution spectra collected with VIMOS at VLT. The targets are faint (20<V<21.5 mag), but the accuracy at the faintest limit is <9 kms-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 RV pattern. We compared the observed RV distribution with N-body simulations for a former disky dwarf galaxy orbiting a giant MilkyWay-like galaxy (Lokas et al. 2015). We rotated the simulated galaxy by 60 degrees with respect to the major axis, we kept the observer on orbital plane of the dwarf and extracted a sample of stars similar to the observed one. Observed and predicted Vrot/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.

21 pages, 16 figures, 4 tables. Accepted for publication in ApJ

References in corpus (14)

• A common mass scale for satellite galaxies of the Milky Way
• Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies
• Stellar Velocities in the Carina, Fornax, Sculptor and Sextans dSph Galaxies: Data from the Magellan/MMFS Survey
• The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run?
• Exploring Halo Substructure with Giant Stars XI: The Tidal Tails of the Carina Dwarf Spheroidal and the Discovery of Magellanic Cloud Stars in the Carina Foreground
• The orbital poles of Milky Way satellite galaxies: a rotationally supported disc-of-satellites
• Scaling Relations and the Fundamental Line of the Local Group Dwarf Galaxies
• Exploring Halo Substructure with Giant Stars X. Extended Dark Matter or Tidal Disruption?: The Case for the Leo I Dwarf Spheroidal Galaxy
• The mass and velocity anisotropy of the Carina, Fornax, Sculptor and Sextans dwarf spheroidal galaxies
• Mass modelling of dwarf spheroidal galaxies: the effect of unbound stars from tidal tails and the Milky Way
• Systemic Proper Motions of Milky Way Satellites from Stellar Redshifts: the Carina, Fornax, Sculptor and Sextans Dwarf Spheroidals
• The ACS LCID project. X. The Star Formation History of IC 1613: Revisiting the Over-Cooling Problem
• The episodic Star Formation History of the Carina Dwarf Spheroidal Galaxy
• The Carina Project VII: Towards the breaking of the age-metallicity degeneracy of red giant branch stars using the c_UBI index

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• Evidence for multiple nucleosynthetic processes from carbon enhanced metal-poor stars in the Carina dwarf spheroidal galaxy
• Dwarf galaxies as a probe of a primordially magnetized Universe
• Tidally induced velocity gradients in the Milky Way dwarf spheroidal satellites
• Constraining neutrino-DM interactions with Milky Way dwarf spheroidals and supernova neutrinos
• Multiple stellar populations in Schwarzschild modeling and the application to the Fornax dwarf