A near zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy

Details A near zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy A near zero velocity dispersion stellar component in the Canes Venatici dwarf spheroidal galaxy

2006-09-04

arxiv.org/abs/astro-ph/0609077v1

Mon.Not.Roy.Astron.Soc.Lett. 373 (2006) L70-L74

Astronomy and Astrophysics

Astrophysics

5 pages, 7 figures, accepted by MNRAS

Scientific paper

10.1111/j.1745-3933.2006.00245.x

We present a spectroscopic survey of the newly-discovered Canes Venatici dwarf galaxy using the Keck/DEIMOS spectrograph. Two stellar populations of distinct kinematics are found to be present in this galaxy: an extended, metal-poor component, of half-light radius 7'.8(+2.4/-2.1), which has a velocity dispersion of 13.9(+3.2/-2.5) km/s, and a more concentrated (half-light radius 3'.6(+1.1/-0.8) metal-rich component of extremely low velocity dispersion. At 99% confidence, the upper limit to the central velocity dispersion of the metal-rich population is 1.9 km/s. This is the lowest velocity dispersion ever measured in a galaxy. We perform a Jeans analysis on the two components, and find that the dynamics of the structures can only be consistent if we adopt extreme (and unlikely) values for the scale length and velocity dispersion of the metal-poor population. With a larger radial velocity sample and improved measurements of the density profile of the two populations, we anticipate that it will be possible to place strong constraints on the central distribution of the dark matter in this galaxy.

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