# Population gradient in Sextans dSph: Comprehensive mapping of a dwarf galaxy by Suprime-Cam

## TL;DR

This study provides a detailed mapping of the Sextans dwarf spheroidal galaxy, revealing age and spatial gradients among its stellar populations, and suggesting a complex evolutionary history with possible remnants of a disrupted star cluster.

## Contribution

It offers the first comprehensive radial and spatial analysis of multiple stellar populations in Sextans dSph using deep wide-field photometry from Subaru/Suprime-Cam.

## Key findings

- Younger stars are more centrally concentrated than older stars.
- Blue HB stars are more spatially extended than red HB stars.
- The galaxy shows an age gradient with younger populations more centrally located.

## Abstract

We present the deep and wide $V$ and $I_c$ photometry of the Sextans dwarf spheroidal galaxy (dSph) taken by Suprime-Cam imager on the Subaru Telescope, which extends out to the tidal radius. The colour-magnitude diagram (CMD) reaches two magnitudes below the main sequence (MS) turn-off, showing a steep red giant branch, blue and red horizontal branch (HB), sub-giant branch (SGB), MS, and blue stragglers (BS). We construct the radial profile of each evolutionary phase and demonstrate that blue HB stars are more spatially extended, while red HB stars are more centrally concentrated than the other components. The colour distribution of SGB stars also varies with the galactocentric distance; the inner SGB stars shift bluer than those in the outskirt. The radial differences in the CMD morphology indicate the existence of the age gradient. The relatively younger stars ($\sim10$ Gyr) are more centrally concentrated than the older ones ($\sim13$ Gyr). The spatial contour maps of stars in different age bins also show that the younger population has higher concentration and higher ellipticity than the older one. We also detect the centrally concentrated bright BS stars, the number of which is consistent with the idea that a part of these stars belongs to the remnant of a disrupted star cluster discovered in the previous spectroscopic studies.