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Deep wide-field imaging down to the oldest main sequence turn-offs in the Sculptor dwarf spheroidal galaxy

journal contribution
posted on 2023-05-17, 06:09 authored by de Boer, TJL, Tolstoy, E, Saha, A, Olsen, K, Irwin, MJ, Battaglia, G, Hill, V, Shetrone, MD, Fiorentino, G, Andrew ColeAndrew Cole
We present wide-field photometry of resolved stars in the nearby Sculptor dwarf spheroidal galaxy using CTIO/MOSAIC, going down to the oldest main sequence turn-off. The accurately flux calibrated wide field colour-magnitude diagrams can be used to constrain the ages of different stellar populations, and also their spatial distribution. The Sculptor dSph contains a predominantly ancient stellar population (>10 Gyr old) which can be easily resolved into individual stars. A galaxy dominated by an old population provides a clear view of ancient processes of galaxy formation unimpeded by overlying younger populations. By using spectroscopic metallicities of RGB stars in combination with our deep main sequence turn-off photometry we can constrain the ages of different stellar populations with particular accuracy. We find that the known metallicity gradient in Sculptor is well matched to an age gradient. This is the first time that this link with age has been directly quantified. This gradient has been previously observed as a variation in horizontal branch properties and is now confirmed to exist for main sequence turn-offs as well. It is likely the Sculptor dSph first formed an extended metal-poor population at the oldest times, and subsequent more metal-rich, younger stars were formed more towards the centre until the gas was depleted or lost roughly 7 Gyr ago. The fact that these clear radial gradients have been preserved up to the present day is consistent with the apparent lack of signs of recent tidal interactions.

History

Publication title

Astronomy and Astrophysics

Volume

528

Issue

Apr

Article number

A119

Number

A119

Pagination

1-22

ISSN

0004-6361

Department/School

School of Natural Sciences

Publisher

E D P Sciences

Place of publication

7, Ave Du Hoggar, Parc D Activites Courtaboeuf, Bp 112, Les Ulis Cedexa, France, F-91944

Rights statement

Copyright © EDP Sciences,

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the physical sciences

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