• DOI:10.1088/0004-637X/751/1/46
• Corpus ID: 6596849

THE DYNAMICS AND METALLICITY DISTRIBUTION OF THE DISTANT DWARF GALAXY VV124

@article{Kirby2012THEDA,
  title={THE DYNAMICS AND METALLICITY DISTRIBUTION OF THE DISTANT DWARF GALAXY VV124},
  author={Evan N. Kirby and Judith G. Cohen and Michele Bellazzini},
  journal={The Astrophysical Journal},
  year={2012},
  volume={751}
}

• E. Kirby, J. Cohen, M. Bellazzini
• Published 20 March 2012
• Physics, Geology
• The Astrophysical Journal

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 〈vr〉 = −29.1 ± 1.3 km s−1 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−1 on any rotation in the photometric disk-like feature. The velocity dispersion is σv = 9.4 ± 1.0 km s−1, from which we inferred a mass of M1/2 = (2.1 ± 0.2) × 107 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.