The NGC3109 Satellite System: The First Systematic Resolved Search for Dwarf Galaxies Around a SMC-mass Host

TL;DR

This study conducted the deepest resolved search for dwarf galaxies around NGC3109, revealing its satellite system and comparing it with theoretical models, thus providing new insights into galaxy formation at SMC-mass scales.

Contribution

First systematic resolved search for dwarf satellites around an SMC-mass host, using deep DECam imaging and semi-resolved methods, identifying known and new candidate satellites.

Findings

Recovered known satellites Antlia and Antlia B.

Detected dwarf galaxies as faint as M_V ~ -6.0.

NGC 3109 has more bright satellites than some CDM predictions.

Abstract

We report the results of the deepest search to date for dwarf galaxies around NGC3109, a barred spiral galaxy with a mass similar to that of the Small Magellanic Cloud (SMC), using a semi-automated search method. Using the Dark Energy Camera (DECam), we survey a region covering a projected distance of $\sim$70 kpc of NGC 3109 ($D$ = 1.3 Mpc, $R_\mathrm{vir}\sim$ 90 kpc, $M\sim10^8M_\ast$) as part of the MADCASH and DELVE-DEEP programs. Through our resolved and newly designed semi-resolved searches, we successfully recover the known satellites Antlia and Antlia B. We identified a promising candidate, which was later confirmed to be a background dwarf through deep follow-up observations. Our detection limits are well defined, with the sample $\sim 80\%$ complete down to $M_V\sim-$8.0 , and includes detections of dwarf galaxies as faint as $M_V\sim-$6.0. This is the first comprehensive study of a satellite system through resolved star around an SMC mass host. Our results show that NGC 3109 has more bright ($M_V\sim-$9.0) satellites than the mean predictions from cold dark matter (CDM) models, but well within the host-to-host scatter. A larger sample of LMC/SMC-mass hosts is needed to test whether or not the observations are consistent with current model expectations.