The formation and evolution of Andromeda IX

TL;DR

This study investigates the Andromeda IX dwarf galaxy within the Local Group, analyzing its variable stars, star formation history, and distance to understand its formation and evolution.

Contribution

It provides new observational data on LPVs, star formation history, and distance measurement for Andromeda IX, enhancing understanding of dwarf galaxy evolution.

Findings

50 long-period variables identified in Andromeda IX

Star formation rate peaks at approximately 0.00082 M_sun/yr

Distance modulus estimated at 24.56 mag

Abstract

Local Group (LG), the nearest and most complete galactic environment, provides valuable information on the formation and evolution of the Universe. Studying galaxies of different sizes, morphologies, and ages can provide this information. For this purpose, we chose the And\,IX dSph galaxy, which is one of the observational targets of the Isaac Newton Telescope (INT) survey. A total of 50 long-period variables (LPVs) were found in And\,IX in two filters, Sloan $i'$ and Harris $V$ at a half-light radius of 2.5 arcmin. The And\,IX's star formation history (SFH) was constructed with a maximum star formation rate (SFR) of about $0.00082\pm0.00031$ M$_\odot$ yr$^{-1}$, using LPVs as a tracer. The total mass return rate of LPVs was calculated based on the spectral energy distribution (SED) of about $2.4\times10^{-4}$ M$_\odot$ yr$^{-1}$. The distance modulus of $24.56_{-0.15}^{+0.05}$ mag was estimated based on the tip of the red giant branch (TRGB).