Galaxy Evolution Explorer Observations of the Ultraviolet Surface Brightness and Color Profiles of the Local Group Elliptical Galaxy M32 (NGC 221)

Abstract

M32, the compact elliptical galaxy companion to the Andromeda spiral galaxy, has been imaged by the Galaxy Evolution Explorer (GALEX) in two UV bands, centered at ∼1500 (far-ultraviolet [FUV]) and 2300 Å (near-ultraviolet). 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 Δ(FUV-B)/Δ 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 [Δ(FUV-B)/Δ log r < -2], inverted with respect to the majority of gradients seen in giant elliptical galaxies. Our new results show that despite its very low UV upturn, M32 has similar UV properties to those observed in luminous elliptical galaxies.