The star formation history of the Sextans dwarf spheroidal galaxy: a true fossil of the pre-reionization era

TL;DR

This study reconstructs the star formation history of the Sextans dwarf galaxy, revealing it ceased star formation shortly after reionization, likely due to supernova-driven gas removal, making it a fossil of the early universe.

Contribution

It provides the first detailed SFH of Sextans from deep photometry, showing it stopped forming stars early and highlighting supernova feedback's role in galaxy evolution.

Findings

Sextans stopped star formation less than 1.3 Gyr after the Big Bang.

The main star formation burst lasted about 0.6 Gyr.

Supernovae likely expelled gas, halting further star formation.

Abstract

We present the star formation history (SFH) of the Sextans dwarf spheroidal galaxy based on deep archive $B$,$I$ photometry taken with Suprime-Cam at Subaru telescope focusing our analysis on the inner region of the galaxy, fully located within the core radius. Within the errors of our SFH we have not detected any metallicity gradient along the considered radial distance interval. As a main result of this work we can state that the Sextans dwarf spheroidal stopped forming stars less than $\sim1.3$ Gyr after Big Bang in correspondance to the end of the reionization epoch. We have been able to constrain the duration of the main burst of star formation to $\sim0.6$ Gyr. From the calculation of the mechanical luminosity released from supernovae (SNe) during the brief episode of star formation, there are strong indications that SNe could have played an important role in the fate of Sextans, by removing almost completely the gas component, so preventing a prolonged star formation.