Discovery of New Dwarf Galaxy near The Isolated Spiral Galaxy NGC 6503

TL;DR

This paper reports the discovery and detailed characterization of a new dwarf galaxy near NGC 6503, highlighting its properties, stellar populations, and the absence of massive O-stars, contributing to understanding dwarf galaxy features.

Contribution

The study presents the first detailed observation and analysis of a new dwarf galaxy, including its structural properties and stellar populations, expanding knowledge of dwarf galaxies in isolated environments.

Findings

Discovered a new dwarf galaxy NGC6503-d1 near NGC 6503.

The dwarf galaxy has a V magnitude of -10.5 and a half-light radius of 400 pc.

Detected an HII region with low Halpha luminosity, indicating few O-stars.

Abstract

We report the discovery of a new dwarf galaxy (NGC6503-d1) during the Subaru extended ultraviolet (XUV) disk survey. It is a likely companion of the spiral galaxy NGC6503. The resolved images, in B, V, R, i, and Halpha, show an irregular appearance due to bright stars with underlying, smooth and unresolved stellar emission. It is classified as the transition type (dIrr/dSph). Its structural properties are similar to those of the dwarfs in the Local Group, with a V absolute magnitude ~ -10.5, half-light radius ~400 pc, and central surface brightness ~25.2. Despite the low stellar surface brightness environment, one HII region was detected, though its Halpha luminosity is low, indicating an absence of any appreciable O-stars at the current epoch. The presence of multiple stellar populations is indicated by the color-magnitude diagram of ~300 bright resolved stars and the total colors of the dwarf, with the majority of its total stellar mass ~4x10^6 Msun in an old stellar population.