TY - JOUR
T1 - A search for Extended Ultraviolet Disk (XUV-disk) galaxies in the local universe
AU - Thilker, David A.
AU - Bianchi, Luciana
AU - Meurer, Gerhardt
AU - De Paz, Armando Gil
AU - Boissier, Samuel
AU - Madore, Barry F.
AU - Boselli, Alessandro
AU - Ferguson, Annette M.N.
AU - Muńoz-Mateos, Juan Carlos
AU - Madsen, Greg J.
AU - Hameed, Salman
AU - Overzier, Roderik A.
AU - Forster, Karl
AU - Friedman, Peter G.
AU - Martin, D. Christopher
AU - Morrissey, Patrick
AU - Neff, Susan G.
AU - Schiminovich, David
AU - Seibert, Mark
AU - Small, Todd
AU - Wyder, Ted K.
AU - Donas, José
AU - Heckman, Timothy M.
AU - Lee, Young Wook
AU - Milliard, Bruno
AU - Rich, R. Michael
AU - Szalay, Alex S.
AU - Welsh, Barry Y.
AU - Yi, Sukyoung K.
PY - 2007/12
Y1 - 2007/12
N2 - We have initiated a search for extended ultraviolet disk (XUV-disk) galaxies in the local universe. Here we compare GALEX UV and visible-NIR images of 189 nearby (D < 40 Mpc) S0-Sm galaxies included in the GALEX Atlas of Nearby Galaxies and present the first catalog of XUV-disk galaxies. We find that XUV-disk galaxies are surprisingly common but have varied relative (UV/optical) extent and morphology. Type 1 objects (≳20% incidence) have structured, UV-bright/optically faint emission features in the outer disk, beyond the traditional star formation threshold. Type 2 XUV-disk galaxies (∼10% incidence) exhibit an exceptionally large, UV-bright/optically low surface brightness (LSB) zone having blue UV-Ks outside the effective extent of the inner, older stellar population, but not reaching extreme galactocentric distance. If the activity occurring in XUV-disks is episodic, a higher fraction of present-day spirals could be influenced by such outer disk star formation. Type 1 disks are associated with spirals of all types, whereas Type 2 XUV-disks are predominantly found in late-type spirals. Type 2 XUV-disks are forming stars quickly enough to double their (currently low) stellar mass in the next Gyr (assuming a constant star formation rate). XUV-disk galaxies of both types are systematically more gas-rich than the general galaxy population. Minor external perturbation may stimulate XUV-disk incidence, at least for Type 1 objects. XUV-disks are the most actively evolving galaxies growing via inside-out disk formation in the current epoch, and may constitute a segment of the galaxy population experiencing significant, continued gas accretion from the intergalactic medium or neighboring objects.
AB - We have initiated a search for extended ultraviolet disk (XUV-disk) galaxies in the local universe. Here we compare GALEX UV and visible-NIR images of 189 nearby (D < 40 Mpc) S0-Sm galaxies included in the GALEX Atlas of Nearby Galaxies and present the first catalog of XUV-disk galaxies. We find that XUV-disk galaxies are surprisingly common but have varied relative (UV/optical) extent and morphology. Type 1 objects (≳20% incidence) have structured, UV-bright/optically faint emission features in the outer disk, beyond the traditional star formation threshold. Type 2 XUV-disk galaxies (∼10% incidence) exhibit an exceptionally large, UV-bright/optically low surface brightness (LSB) zone having blue UV-Ks outside the effective extent of the inner, older stellar population, but not reaching extreme galactocentric distance. If the activity occurring in XUV-disks is episodic, a higher fraction of present-day spirals could be influenced by such outer disk star formation. Type 1 disks are associated with spirals of all types, whereas Type 2 XUV-disks are predominantly found in late-type spirals. Type 2 XUV-disks are forming stars quickly enough to double their (currently low) stellar mass in the next Gyr (assuming a constant star formation rate). XUV-disk galaxies of both types are systematically more gas-rich than the general galaxy population. Minor external perturbation may stimulate XUV-disk incidence, at least for Type 1 objects. XUV-disks are the most actively evolving galaxies growing via inside-out disk formation in the current epoch, and may constitute a segment of the galaxy population experiencing significant, continued gas accretion from the intergalactic medium or neighboring objects.
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U2 - 10.1086/523853
DO - 10.1086/523853
M3 - Article
AN - SCOPUS:39449112767
SN - 0067-0049
VL - 173
SP - 538
EP - 571
JO - Astrophysical Journal, Supplement Series
JF - Astrophysical Journal, Supplement Series
IS - 2
ER -