A Search for Extended Ultraviolet Disk (XUV-Disk) Galaxies in the Local Universe

By D. Thilker, L. Bianchi, G. Meurer, A. Gil de Paz, S. Boissier, B. Madore, A. Boselli, A. Ferguson, J. Muńoz-Mateos, G. Madsen and 19 more. 2007

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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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/274b04231eb33a3ffda8e9438ce1315019f54d12

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Citations in the corpus

COMPARISON OF Hα AND UV STAR FORMATION RATES IN THE LOCAL VOLUME: SYSTEMATIC DISCREPANCIES FOR DWARF GALAXIES (2009, background): “Such statistical effects on the Hα luminosity has been previously explored for example by Boissier et al. (2007) and Thilker et al. (2007) in the context of extended UV disks.”
Physical properties and environments of nearby galaxies (2009, background): “Thilker et al. (2007) has recently reported from GALEX imaging that over 20% of spiral galaxies have significant UV emission in the outer disk.”
Gaseous Galaxy Halos (2012, background): “A large reservoir of fuel is in the outer parts of the disk where few stars are currently forming (Werk et al., 2010a; Thilker et al., 2007), and the flat metallicity gradients in gas disks indicate transport mechanisms are active (Werk et al., 2010b, 2011; Bresolin et al., 2009; Spitoni &…”
A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA (2013, methodology): “The same pattern in the abundance has been described in the case of the extended UV disks discovered by GALEX (Gil de Paz et al. 2005; Thilker et al. 2007), which show oxygen abundances that are rarely below one-tenth of the solar value.”
Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, background): “It is well known now that the gaseous disk extends well beyond the optical radius (Thilker et al. 2007; Zaritsky & Christlein 2007).”