INT monitoring survey of Local Group dwarf galaxies: star formation history and chemical enrichment

Abstract

The Local Group (LG) hosts many dwarf galaxies with diverse physical characteristics in terms of morphology, mass, star formation, and metallicity. To this end, LG can offer a unique site to tackle questions about the formation and evolution of galaxies by providing detailed information. While large telescopes are often the first choices for such studies, small telescope surveys that perform dedicated observations are still important, particularly in studying bright objects in the nearby universe. In this regard, we conducted a nine epoch survey of 55 dwarf galaxies called the "Local Group dwarf galaxies survey" using the 2.5m Isaac Newton Telescope (INT) in the La Palma to identify Long-Period Variable (LPV) stars, namely Asymptotic Giant Branch (AGB) and Red Super Giant (RSG) stars. AGB stars formed at different times and studying their radial distribution and mass-loss rate can shed light on the structure formation in galaxies. To further investigate the evolutionary path of these galaxies, we construct their star formation history (SFH) using the LPV stars, which are at the final stages of their evolution and therefore experience brightness fluctuations on the timescales between hundred to thousand days. In this paper, we present some of the results of the Local Group dwarf galaxies survey.

The Isaac Newton Telescope Monitoring Survey of Local Group Dwarf Galaxies. V. The Star Formation History of Sagittarius Dwarf Irregular Galaxy Derived from Long-period Variable Stars

“…This work is part of the Isaac Newton Telescope monitoring survey of LG dwarf galaxies. Various types of dwarf galaxies, including 43 dwarf spheroidals, six dIrrs, six dwarf transition galaxies, and four globular clusters come under the scrutiny of our team (Saremi et al 2017;Parto et al 2021). The main objectives of this survey include identifying all LPVs in the dwarf galaxies of the LG observable in the northern hemisphere; obtaining accurate time-averaged photometry for all LPVs; constructing the SFHs from LPVs luminosity distribution; obtaining their pulsation amplitude; modeling their spectral energy distributions; and studying their mass loss as a function of stellar properties such as mass, luminosity, metallicity, and pulsation amplitude (Saremi et al 2020).…”