The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy VV124

Abstract

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/DEIMOS spectrograph. 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 <v_r> = -29.1 +/- 1.3 km/s, in agreement with the previous radio measurements of HI 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 sigma_v = 9.4 +/- 1.0 km/s, from which we inferred a mass of M_1/2 = (2.1 +/- 0.2) x 10^7 M_sun and a mass-to-light ratio of (M/L_V)_1/2 = 5.2 +/- 1.1 M_sun/L_sun, 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]> = -1.58 +/- 0.06, is consistent with the mass-metallicity relation defined by dwarf spheroidal galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.

16 pages, 14 figures. Accepted to ApJ. The machine-readable Table 2 is available in the source file by clicking on "Other formats." Version 3 corrects a problem that caused the metallicity measurements to be ~0.4 dex too high

References in corpus (17)

• The Kinematics of the Ultra-Faint Milky Way Satellites: Solving the Missing Satellite Problem
• Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
• The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
• The Baryon Content of Extremely Low Mass Dwarf Galaxies
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. II. Catalog of Stars in Milky Way Dwarf Satellite Galaxies
• Leo A: A Late-Blooming Survivor of the Epoch of Reionization in the Local Group
• The Unorthodox Orbits of Substructure Halos
• Scaling Relations and the Fundamental Line of the Local Group Dwarf Galaxies
• Metallicity and Alpha-Element Abundance Measurement in Red Giant Stars from Medium Resolution Spectra
• Exploring Halo Substructure with Giant Stars X. Extended Dark Matter or Tidal Disruption?: The Case for the Leo I Dwarf Spheroidal Galaxy
• The Hubble flow around the Local Group
• Exploring Halo Substructure with Giant Stars: The Dynamics and Metallicity of the Dwarf Spheroidal in Bootes
• The mass-metallicity gradient relation of early-type galaxies
• A large stellar evolution database for population synthesis studies. IV. Integrated properties and spectra
• A New Method for Isolating M31 Red Giant Stars: The Discovery of Stars out to a Radial Distance of 165 Kiloparsecs
• The Star Formation History of Isolated Dwarf UGC4879

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• The extended structure of the dwarf irregular galaxies Sextans A and Sextans B. Signatures of tidal distortion in the outskirts of the Local Group
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• Solo dwarfs II: The stellar structure of isolated Local Group dwarf galaxies
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