11) Studying the early chemical evolution of dwarf galaxies in different environments with RR Lyrae stars

Abstract: RR Lyrae stars (RRLs) are powerful tracers of the early evolution of their host stellar system since they provide direct insight into the age and the chemical evolution of the old (>10 Gyr) population they belong to. Their pulsation properties can be used to obtain individual metallicities and derive the metallicity distribution of a purely old population. The large sample of RRLs in the Sculptor dSph allowed us to trace in detail the early chemical evolution of this galaxy. We have found that a large metallicity spread is present in the population of RRLs, consistent with a rapid chemical enrichment that occurred at the early stages of Sculptor’s life. Also, when comparing the metallicity distribution of the RRLs (purely old population) with the RGB stars (age-degenerate population) we can constrain the timescales for the outside-in evolution of this galaxy, which lasted substantially longer in the inner than in the outer parts. We have extended our approach to several Milky Way and M31 dwarfs satellites (observed with HST), deriving metallicities for individual RRLs and providing their metallicity distribution function, and have compared the two different environments. We have found robust evidence of an early chemical enrichment in the old population of some of them. Finally, we have broadened our study to several more distant dwarf galaxies (Local and Sculptor Group) to illustrate the potential of our approach when the JWST, Roman Telescope and the next generation of ELTs will be operative.

Bio: I am Clara Martínez-Vázquez, postdoc at Cerro Tololo Inter-American Observatory (CTIO)/NSF’s NOIRLab and a member of the DECam science support team. I’m interested in stellar population, galaxy formation and evolution of Local Group dwarf galaxies. My main research is focused on the study of RR Lyrae variable stars, one of the most ancient components of the Local Group dwarf galaxies, which help us to investigate the formation and evolution that occurred at the early stages of a galaxy’s life.