Dwarf galaxy discoveries from the KMTNet supernova programme – III. The Milky-Way analogue NGC 2997 group

Abstract

ABSTRACT We present the discovery of 48 new and the analysis of 55, including seven previously discovered dwarf galaxy candidates (DGCs) around the giant spiral galaxy NGC 2997 using deep BVI images from the Korea Microlensing Telescope Network Supernova Programme. Their V-band central surface brightness and total absolute magnitudes are in the range of 20.3–26.7 mag arcsec−2 and −(8.02–17.69) mag, respectively, while the I-band effective radii are 0.14–2.97 kpc. We obtain $\alpha \, \simeq$ −1.43 ± 0.02 for the faint-end slope of their luminosity function, comparable to previously measured values but shallower than theoretical predictions based on Λ cold dark matter models. The distance-independent distributions of their mass and colour suggest that the group could have recently accreted new massive members from the surrounding fields. The systematically bluer colours of the brighter members indicate younger stellar population and higher star formation activities in them, which appears to be consistent with similar findings from the SAGA or ELVES survey. We suggest that the massive and bluer dwarf galaxies in the group have experienced less environmental quenching due to their recent accretion, while environmental quenching has been more effective for the low-mass members. The interpretation of NGC 2997 being populationally young with recent accretion of massive members is also consistent with the overall morphological distribution of the dwarf galaxies showing a lack of morphologically evolved candidates but a plethora of irregularly shaped ones. Our detection rate of DGCs in the NGC 2997 group and their inferred star formation activities are comparable to those found in Milky Way analogue systems from recent surveys within the magnitude limit M$_{V}\, \lesssim$ −13 mag.