Faint satellite population of the NGC-3175 Group – a Local Group analogue

In this paper, we identify and study the properties of low-mass dwarf satellites of a nearby Local Group analogue – the NGC-3175 galaxy group with the goal of investigating the nature of the lowest mass galaxies and the ‘Missing Satellites’ problem. Deep imaging of nearby groups such as NGC-3175 is one of the only ways to probe these low-mass galaxies which are important for problems in cosmology, dark matter and galaxy formation. We discover 553 candidate dwarf galaxies in the group, the vast majority of which have never been studied before. We obtained R and B band imaging, with the European Southern Observatory 2.2 m, around the central ∼500 kpc region of NGC-3175, allowing us to detect galaxies down to ∼23 mag (MB ∼ −7.7 mag) in the B band. In the absence of spectroscopic information, dwarf members and likely background galaxies are separated using colour, morphology, and surface brightness criteria. We compare the observed size, surface brightness, and mass scaling relations to literature data. The luminosity function with a faint end slope of α = −1.31, is steeper than that observed in the Local Group. In comparison with simulations, we find that our observations are between a pure Λ cold dark matter model and one involving baryonic effects, removing the apparent problem of finding too few satellites as seen around the Milky Way.