Old or Young? Giant Bulge-Dominated Low-Surface Brightness Galaxies

Low surface brightness galaxies (LSBs) might appear opticallyunimpressive, but the largest LSBs contain as many stars as the largestnormal elliptical and spiral galaxies. Very little is known about theirX-ray properties. We propose short XMM-Newton observations of threegiant, bulge-dominated LSBs that cover over a factor of four in K-bandluminosity to create the first X-ray LSB sample, and compare their L_X/L_Kscaling relation with normal early-type spiral bulges/ellipticals. Wewill also search for AGN in the nuclei and ULXs in the faint disks ofthese intriguing systems.