Stellar Halos from the The Dragonfly Edge-on Galaxies Survey

Abstract

We present the primary results from the Dragonfly Edge-on Galaxies Survey, an exploration of the stellar halos of twelve nearby ( d < 25 Mpc) edge-on disk galaxies with the Dragonfly Telephoto Array. The edge-on orientation of these galaxies allows their stellar halos to be explored with minimal obscuration by or confusion with the much brighter disk light. Galaxies in the sample span a range of stellar masses from 10 9.68 to 10 10.88 M ⊙ . We confirm that the wide range of stellar halo mass fractions previously seen for Milky Way–mass galaxies is also found among less massive spiral galaxies. The scatter in stellar halo mass fraction is large, but we do find a significant positive correlation between stellar halo mass fraction and total stellar mass when the former is measured beyond five half-mass radii. Reasonably good agreement is found with predictions from cosmological hydrodynamical simulations, although observed stellar halo fractions appear to be somewhat lower than expected from these simulations.