Metallicity distribution of the progenitor of the Giant Stellar Stream in the Andromeda Galaxy

TL;DR

This study uses numerical and Monte Carlo simulations to analyze the metallicity distribution of the progenitor dwarf galaxy that formed the Giant Stellar Stream in Andromeda, revealing a negative metallicity gradient and transient double peaks.

Contribution

It presents a detailed simulation-based reconstruction of the progenitor's metallicity distribution, including the origin of observed double peaks, based on the stream's properties.

Findings

Progenitor dwarf galaxy had a negative metallicity gradient of -0.3 ± 0.2.

The double peak metallicity distribution is a transient feature from merger dynamics.

The GSS was formed approximately 2.4 to 2.9 Gyrs ago.

Abstract

The Giant Stellar Stream (GSS) is a prominent tidal feature in the halo of the Andromeda Galaxy (M31), representing the ongoing destruction of a satellite galaxy. In this paper, we investigate the formation of the GSS through detailed numerical simulations of the tidal disruption of a progenitor system. Assuming that the stream was created in a single merger event between M31 and a dwarf spheroidal galaxy with stellar mass of $10^{9}M_{\odot}$, we successfully reproduce the dynamical properties of the GSS. As the metallicity distribution along the stream has been well determined from the observations (PAndAS and AMIGA data sets), we use Monte Carlo simulations to reconstruct the original metallicity distribution of the dwarf progenitor. We find that a progenitor dwarf galaxy with a negative radial metallicity gradient, $\Delta$FeH = -$0.3 \pm 0.2$, reproduces the observed GSS properties at a time between 2.4 and 2.9 Gyrs into the merger. We also show that the observed double peak metallicity distribution along the stream is a transitory structure caused by unique merger circumstances where two groups of streaming stars are moving in opposite directions, intersecting to produce the peaks.