A VLT/FORS2 spectroscopic survey of individual stars in a transforming dwarf galaxy

TL;DR

This study uses VLT/FORS2 spectroscopy to analyze individual stars in the Phoenix dwarf transition galaxy, providing insights into its velocity and metallicity, and shedding light on dwarf galaxy evolution.

Contribution

It presents the first wide-area spectroscopic survey of the Phoenix dwarf transition galaxy, measuring velocities and metallicities of individual stars to understand its evolutionary state.

Findings

Line-of-sight velocities of stars in Phoenix dT

Metallicity distribution of Red Giant Branch stars

Evidence of gas loss process in dwarf galaxy

Abstract

Understanding the properties of dwarf galaxies is important not only to put them in their proper cosmological context, but also to understand the formation and evolution of the most common type of galaxies. Dwarf galaxies are divided into two main classes, dwarf irregulars (dIrrs) and dwarf spheroidals (dSphs), which differ from each other mainly because the former are gas-rich objects currently forming stars, while the latter are gas-deficient with no on-going star formation. Transition types (dT) are thought to represent dIs in the process of losing their gas, and can therefore shed light into the possible process of dwarf irregulars (dIrrs) becoming gas-deficient, passively evolving galaxies. Here we present preliminary results from our wide-area VLT/FORS2 MXU spectroscopic survey of the Phoenix dT, from which we obtained line-of-sight velocities and metallicities from the nIR Ca II triplet lines for a large sample of individual Red Giant Branch stars.