Giant Galaxies, Dwarfs, and Debris Survey. I. Dwarf Galaxies and Tidal Features Around NGC 7331

TL;DR

This study uses deep imaging to identify dwarf galaxies and tidal features around NGC 7331, revealing a few low-luminosity satellites and a possible tidal stream, providing insights into galaxy interactions in small groups.

Contribution

First detailed imaging survey of NGC 7331's surroundings, identifying dwarf candidates and tidal features, and comparing its satellite system to other nearby spirals.

Findings

Detected four dwarf galaxy candidates with properties consistent with dSph.

Identified a faint stellar stream possibly resulting from tidal interaction.

NGC 7331 has fewer early-type satellites compared to other giant spirals.

Abstract

The Giant GAlaxies, Dwarfs, and Debris Survey concentrates on the nearby universe to study how galaxies have interacted in groups of different morphology, density, and richness. In these groups we select the dominant spiral galaxy and search its surroundings for dwarf galaxies and tidal interactions. This paper presents the first results from deep wide-field imaging of NGC 7331, where we detect only four low luminosity candidate dwarf companions and a stellar stream that may be evidence of a past tidal interaction. The dwarf galaxy candidates have surface brightnesses of mu_{r} ~ 23-25 mag/arcsec^{2} with (g-r) colors of 0.57-0.75mag in the Sloan Digital Sky Survey filter system, consistent with their being dwarf spheroidal galaxies (dSph). A faint stellar stream structure on the western edge of NGC 7331 has mu_{g} ~27 mag/arcsec^{2} and a relatively blue color of (g-r)=0.15mag. If it is tidal debris, then this stream could have probably formed from a rare type of interaction between NGC 7331 and a dwarf irregular or transition-type dwarf galaxy. We compare the structure and local environments of NGC 7331 to those of other nearby giant spirals in small galaxy groups. NGC 7331 has a much lower (2%) stellar mass in the form of early-type satellites than found for M31 and lacks the presence of nearby companions like luminous dwarf elliptical galaxies or the Magellanic Clouds. However, our detection of a few dSph candidates suggests that it is not deficient in low-luminosity satellites.