Astrophys. J., 751, 46 (2012/May-3)
The dynamics and metallicity distribution of the distant dwarf galaxy VV124.
KIRBY E.N., COHEN J.G. and BELLAZZINI M.
Abstract (from CDS):
VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial velocities for different components of the galaxy, and photometry hinted at the presence of a stellar disk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS). We validated members based on their positions in the color-magnitude diagram, radial velocities, and spectral features. Our sample contains 67 members. The average radial velocity is r> = -29.1±1.3 km/s in agreement with the previous radio measurements of H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by velocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an upper limit of 8.6 km/s on any rotation in the photometric disk-like feature. The velocity dispersion is σ_ v_= 9.4±1.0 km/s, from which we inferred a mass of M1/2= (2.1 ±0.2)x107 M☉ and a mass-to-light ratio of (M/LV)1/2= 5.2±1.1 M☉/L☉, both measured within the half-light radius. Thus, VV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines. The average metallicity, <[Fe/H]> = -1.14±0.06, is consistent with the mass-metallicity relation defined by dSph galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.
galaxies: abundances - galaxies: dwarf - galaxies: individual: VV124 - galaxies: kinematics and dynamics - Local Group
VizieR on-line data:
<Available at CDS (J/ApJ/751/46): table2.dat>
Table 2: [KCB2012] NNNNN N=131 among (Nos 1167-17428).
erratum vol. 768, art. 96 (2013)
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