2017/02/15 by Shany Danieli, Pieter van Dokkum, Allison Merritt +6 · 4 citations
Environmental Science · Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy group #Luminosity #Luminosity function #Luminous infrared galaxy #Physics #Remote Sensing in Agriculture #Spiral galaxy #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa615b
Accepted for publication in ApJ
arxiv created 2017/02/15 · openalex created_date 2017/03/03 · openalex publication_date 2017/03/10 · arxiv updated 2017/03/22 · openalex updated_date 2026/08/05
Abstract We obtained follow-up HST observations of the seven low surface brightness galaxies discovered with the Dragonfly Telephoto Array in the field of the massive spiral galaxy M101. Out of the seven galaxies, only three were resolved into stars and are potentially associated with the M101 group at D = 7 Mpc. Based on HST ACS photometry in the broad F606W and F814W filters, we use a maximum likelihood algorithm to locate the Tip of the Red Giant Branch in galaxy color–magnitude diagrams. Distances are and and we confirm that they are members of the M101 group. Combining the three confirmed low-luminosity satellites with previous results for brighter group members, we find the M101 galaxy group to be a sparsely populated galaxy group consisting of seven group members, down to M V = −9.2 mag. We compare the M101 cumulative luminosity function to that of the Milky Way and M31. We find that they are remarkably similar; in fact, the cumulative luminosity function of the M101 group gets even flatter for fainter magnitudes, and we show that the M101 group might exhibit the two known small-scale flaws in the ΛCDM model, namely “the missing satellite” problem and the “too big to fail” problem. Kinematic measurements of M101's satellite galaxies are required to determine whether the “too big to fail” problem does in fact exist in the M101 group.