The M101 galaxy group as a node in the 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]$^{\circ}$, SGB =[10 -- 37]$^{\circ}$ spanning a chain of galaxies: M\,63, M\,51, M\,101, and NGC\,6503, based on the data from DESI Legacy Imaging Surveys. Six new supposed dwarf members of the complex were discovered. 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 $(1.02\pm0.42)\times10^{12}~M_{\odot}$ and $(16.0\pm6.5)~M_{\odot}/L_{\odot}$, respectively. We notice that the average dark mass-to-luminosity ratio in the groups around M\,63, M\,51, and M\,101 is $(12\pm4)M_{\odot}/L_{\odot}$ that almost an order of magnitude lower than the global cosmic ratio, $(102\pm5)M_{\odot}/L_{\odot}$.