The pride of lions around Messier 105

Abstract

ABSTRACTWe undertook a search for new dwarf galaxies in the Leo-I group using the data from the DECaLS digital sky survey. Five new presumed members of this group have been found in a wide vicinity of ${\rm M}\, 105 ({\rm NGC}\, 3379$). Currently, the group has a population of 83 galaxies, 33 of which have measured radial velocities. More than half of the group members belong to early types with no signs of ongoing star formation. About a quarter of the galaxies are outside the group’s virial radius, R= 385 kpc. The presence of multiple systems with a size of about 15 kpc is evident in the group, but there are no noticeable global flat or filamentary substructures. The luminosity function of the group looks to be deficient in galaxies with absolute magnitudes in the interval MB = [−18, −15] mag. The ${\rm M}\, 105$ group is characterized by a radial velocity dispersion of 136 km s−1, orbital mass estimate (5.76 ± 1.32) × 1012 M⊙, and the total mass-to-K-band-luminosity ratio (17.8 ± 4.1)M⊙/L⊙. The neighbouring group of galaxies around ${\rm M}\, 66 ({\rm NGC}\, 3627$) has a similar virial radius, 390 kpc, velocity dispersion, 135 km s−1, and total mass-to-luminosity ratio, (15.6 ± 3.9)M⊙/L⊙. Both groups in the Leo constellation are approaching the Local Group with a velocity of about 100 km s−1. In the background of the ${\rm M}\, 105$ group, we noted a group of 6 galaxies with an unusually low virial mass-to-luminosity ratio, MT/LK = (4.1 ± 2.2) M⊙/L⊙.