2016/05/09 by C. E. Martínez-Vázquez, M. Monelli, C. Gallart +8 · 1 citation
Physics and Astronomy · #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1093/mnrasl/slw093
5 pages, 4 figures. Accepted for publication on MNRAS Letters
arxiv created 2016/05/09 · arxiv updated 2016/05/11
We present the metallicity distribution of a sample of 471 RR Lyrae (RRL) stars in the Sculptor dSph, obtained from the I-band Period-Luminosity relation. It is the first time that the early chemical evolution of a dwarf galaxy is characterized in such a detailed and quantitative way, using photometric data alone. We find a broad metallicity distribution (FWHM=0.8 dex) that is peaked at [Fe/H]≃-1.90 dex, in excellent agreement with literature values obtained from spectroscopic data. Moreover, we are able to directly trace the metallicity gradient out to a radius of ∼55 arcmin. We find that in the outer regions (r>∼32 arcmin) the slope of the metallicity gradient from the RRLs (-0.025 dex arcmin-1) is comparable to the literature values based on red giant (RG) stars. However, in the central part of Sculptor we do not observe the latter gradients. This suggests that there is a more metal-rich and/or younger population in Sculptor that does not produce RRLs. This scenario is strengthened by the observation of a metal-rich peak in the metallicity distribution of RG stars by other authors, which is not present in the metallicity distribution of the RRLs within the same central area.