NGC 4656UV: A UV-SELECTED TIDAL DWARF GALAXY CANDIDATE

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 morpho...

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Bibliographic Details
Published in:The Astrophysical journal 2012-05, Vol.750 (2), p.1-16
Main Authors: Schechtman-Rook, Andrew, Hess, Kelley M
Format: Article
Language:English
Subjects:
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
COSMIC DUST
Dwarf galaxies
Dynamical systems
Dynamics
ENERGY SPECTRA
Evolutionary
FAR ULTRAVIOLET RADIATION
GALAXIES
GHZ RANGE
MASS
MORPHOLOGY
NONLUMINOUS MATTER
OPACITY
Parents
PHOTOMETRY
Spectral energy distribution
STARS
Ultraviolet
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Summary: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 sub([middot in circle]) yr super(-1) from the far-ultraviolet flux and measure a total H I mass of 3.8 x 10 super(8) M sub([middot in circle]) 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.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/750/2/171