The M101 galaxy group as a node in the nearby cosmic filament

TL;DR

This study identifies new faint dwarf galaxies around M101, estimates the group's mass, and compares its dark matter-to-luminosity ratio to cosmic averages, highlighting differences in local versus global dark matter distribution.

Contribution

It reports the discovery of six new dwarf galaxy candidates and provides detailed mass and luminosity ratio estimates for the M101 galaxy group.

Findings

Six new dwarf galaxy candidates discovered.

The M101 group has a total mass of approximately 1.02×10^{12} solar masses.

The dark matter-to-luminosity ratio in the group is significantly lower than the cosmic average.

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, $(102\pm5)M_{\odot}/L_{\odot}$.