The M 101 galaxy group as a node in a nearby cosmic filament

Abstract

We performed a search for faint low-surface-brightness dwarf galaxies around the major spiral galaxy M 101 and in the large rectangular area within SGL = [30-80]° and SGB = [10-37]° spanning a chain of galaxies: M 63, M 51, M 101, and NGC 6503. We based our search on data from DESI Legacy Imaging Surveys. We discovered six new probable dwarf members of the complex. We present a list of 25 prospective members of the M 101 group and estimate the total mass and the total-mass-to-K-band-luminosity ratio of the group as (1.02 ± 0.42)×10¹² M_⊙ and (16.0 ± 6.5) M_⊙/L_⊙, respectively. We note that the average dark mass-to-luminosity ratio in the groups around M 63, M 51, and M 101 is (12 ± 4) M_⊙/L_⊙, which is almost an order of magnitude lower than the global cosmic ratio, (102 ± 5) M_⊙/L_⊙.