NGC 4656UV: A UV-selected Tidal Dwarf Galaxy Candidate

Type Journal Article
Names Andrew Schechtman-Rook, Kelley M. Hess
Publication The Astrophysical Journal
Volume 750
Pages 171
Journal Abbreviation The Astrophysical Journal
Date May 1, 2012
DOI 10.1088/0004-637X/750/2/171;
ISSN 0004-637X
Short Title NGC 4656UV
Library Catalog NASA ADS
Abstract We report the discovery of a UV-bright tidal dwarf galaxy (TDG) candidate in the NGC 4631/4656 galaxy group, which we designate NGC 4656UV. Using survey and archival data spanning from 1.4 GHz to the ultraviolet, we investigate the gas kinematics and stellar properties of this system. The H I morphologies of NGC 4656UV and its parent galaxy NGC 4656 are extremely disturbed, with significant amounts of counterrotating and extraplanar gas. From UV-FIR photometry, computed using a new method to correct for surface gradients on faint objects, we find that NGC 4656UV has no significant dust opacity and a blue spectral energy distribution. We compute a star formation rate of 0.027 M ⊙ yr-1 from the far-ultraviolet flux and measure a total H I mass of 3.8 × 108 M ⊙ for the object. Evolutionary synthesis modeling indicates that NGC 4656UV is a low-metallicity system whose only major burst of star formation occurred within the last ~260-290 Myr. The age of the stellar population is consistent with a rough timescale for a recent tidal interaction between NGC 4656 and NGC 4631, although we discuss the true nature of the object—whether it is tidal or pre-existing in origin—in the context of its metallicity being a factor of 10 lower than its parent galaxy. We estimate that NGC 4656UV is either marginally bound or unbound. If bound, it contains relatively low amounts of dark matter. The abundance of archival data allows for a deeper investigation into this dynamic system than is currently possible for most TDG candidates. Based in part on observations made with the NASA Galaxy Evolution Explorer. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.
Tags GALAXIES: INTERACTIONS, GALAXIES: STRUCTURE, Galaxies: Dwarf, galaxies: individual: NGC 4656, galaxies: kinematics and dynamics
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