Variable stars in Local Group Galaxies - I. Tracing the early chemical enrichment and radial gradients in the Sculptor dSph with RR Lyrae stars
Date Issued
2015
Author(s)
Martínez-Vázquez, C. E.
•
Monelli, M.
•
Bono, G.
•
Stetson, P. B.
•
Ferraro, I.
•
Bernard, E. J.
•
Gallart, C.
•
•
Iannicola, G.
•
Udalski, A.
Description
We are very grateful to our referee, Mario Mateo, for his useful comments and suggestions that helped to improve the readability and the content of this paper. We thank S. Cassisi for providing interesting and helpful discussions about the evolution of the stars in the horizontal branch. CEMV thanks V. F. Braga for helping us with the theoretical relations, and is grateful to the Rome Observatory and the Physics Department of the Tor Vergata University where most of this work has been realized. This research has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under the grant (project reference AYA2014–56795). The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. GF has been supported by the Futuro in Ricerca 2013 (grant RBFR13J716).
Abstract
We identified and characterized the largest (536) RR Lyrae (RRL) sample in a Milky Way dSph satellite (Sculptor) based on optical photometry data collected over ̃24 years. The RRLs display a spread in V-magnitude (̃0.35 mag) which appears larger than photometric errors and the horizontal branch (HB) luminosity evolution of a mono-metallic population. Using several calibrations of two different reddening free and metal independent period-Wesenheit relations we provide a new distance estimate μ = 19.62 mag (σμ = 0.04 mag) that agrees well with literature estimates. We constrained the metallicity distribution of the old population, using the MI period-luminosity relation, and we found that it ranges from -2.3 to -1.5 dex. The current estimate is narrower than suggested by low and intermediate spectroscopy of RGBs (∆ [Fe/H]≤ 1.5). We also investigated the HB morphology as a function of the galactocentric distance. The HB in the innermost regions is dominated by red HB stars and by RRLs, consistent with a more metal-rich population, while in the outermost regions it is dominated by blue HB stars and RRLs typical of a metal-poor population. Our results suggest that fast chemical evolution occurred in Sculptor, and that the radial gradients were in place at an early epoch.
Volume
454
Issue
2
Start page
1509
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.454.1509M
Rights
open.access
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