Dragonfly 44 and the Nature of Ultra-Diffuse Galaxies

Dragonfly 44 is an ultradiffuse galaxy with a stellar mass of only 3e8 Msun buta dynamical mass of 1e12 Msun and about 100 globular clusters. This suggeststhat it is a central galaxy that somehow lost its gas, rather than a strippedsatellite. We propose measuring the amount of hot gas, which is the primarysource of fuel for star formation in galaxies of this size, as well as itspresentday star formation rate and number of lowmass Xray binaries. Thesewill provide important clues to the nature of Dragonfly 44 and the thousands ofother known ultradiffuse galaxies. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]