GALEX observations of the UV surface brightness and color profiles of the Local Group elliptical galaxy M32 (NGC221)

Armando Gil de Paz , B. F. Madore , Y. -J. Sohn , Y. -W. Lee , Mark Seibert , Robert Michael Rich , L. Bianchi , T. A. Barlow , Y. -I. Byun , José Donas (1) , K. Forster , P. G. Friedman , T. M. Heckman , P. Jelinsky , R. F. Malina , D. C. Martin , B. Milliard (1) , P. Morrissey , Susan Gale Neff , David Schiminovich , O. H. W. Siegmund , Todd Small , Alex Szalay , B. Y. Welsh , Ted Wyder

1 LAM - Laboratoire d'Astrophysique de Marseille

M32, the compact elliptical-galaxy companion to the Andromeda spiral galaxy has been imaged by the Galaxy Evolution Explorer (GALEX) in two ultraviolet bands, centered at ~1500 (FUV) and 2300 Angstroms (NUV). The imaging data have been carefully decomposed so as to properly account for the complicated background contamination from the disk of M31. We have derived the surface brightness and color profiles finding a slightly positive color gradient of Delta(FUV-B)/Delta log(r)=+0.15+/-0.03 within one effective radius. Earlier data from the Ultraviolet Imaging Telescope suggested that M32 had an extremely large (negative) FUV-optical color gradient (Delta(FUV-B)/Delta log(r)<-2), inverted with respect to the majority of gradients seen in giant elliptical galaxies. Our new results show that, despite of its very low UV-upturn, M32 has similar UV properties to those observed in luminous elliptical galaxies.

Mots clés: galaxies: elliptical and lenticular; cDgalaxies: fundamental parametersgalaxies: individual (M32)Local Groupultraviolet: galaxies

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Armando Gil de Paz, B. F. Madore, Y. -J. Sohn, Y. -W. Lee, Mark Seibert, et al.. GALEX observations of the UV surface brightness and color profiles of the Local Group elliptical galaxy M32 (NGC221). The Astrophysical Journal, 2005, 619L, pp.115. ⟨10.1086/422470⟩. ⟨hal-00015094⟩