A census of dwarf galaxy satellites around LMC-mass galaxy NGC 2403

TL;DR

This study provides the first detailed census of satellite galaxies around NGC 2403, a galaxy similar in mass to the LMC, using deep imaging to identify and analyze satellite candidates and compare their distribution to theoretical models.

Contribution

It offers the first comprehensive satellite census around an LMC-mass galaxy, assessing detection completeness and comparing observed satellite luminosity functions to models.

Findings

Identified 149 satellite candidates, with only one confirmed dwarf galaxy.

Sensitivity to satellites down to M_V ~ -7.5 mag.

Satellite luminosity function agrees with theoretical expectations.

Abstract

We present the first comprehensive census of the satellite population around a Large Magellanic Cloud (LMC) stellar-mass galaxy, as part of the Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) survey. We have surveyed NGC 2403 (D=3.0 Mpc) with the Subaru/Hyper Suprime-Cam imager out to a projected radius of 90 kpc (with partial coverage extending out to ~110 kpc, or ~80% of the virial radius of NGC 2403), resolving stars in the uppermost ~2.5 mags of its red giant branch. By looking for stellar overdensities in the red giant branch spatial density map, we identify 149 satellite candidates, of which only the previously discovered MADCASH J074238+65201-dw is a bona fide dwarf, together with the more massive and disrupting satellite DDO 44. We carefully assess the completeness of our search via injection of artificial dwarf galaxies into the images, finding that we are reliably sensitive to candidates down to M_V ~ -7.5 mag (and somewhat sensitive to even fainter satellites). A comparison of the satellite luminosity function of NGC 2403 down to this magnitude limit to theoretical expectations shows overall good agreement. This is the first of a full sample of 11 Magellanic Cloud-mass host galaxies we will analyze, creating a statistical sample that will provide the first quantitative constraints on hierarchical models of galaxy formation around low-mass hosts.