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The Local Group Dwarf Galaxies. The Star Formation Histories derived using the Long Period Variable Stars

Published online by Cambridge University Press:  30 October 2019

Elham Saremi ,
Atefeh Javadi ,
Jacco Th. van Loon ,
Habib Khosroshahi ,
Sara Rezaei kh Open the ORCID record for Sara Rezaei kh [Opens in a new window] ,
Roya Hamedani Golshan  and
Seyed A. Hashemi
Elham Saremi
Affiliation:
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5531, Iran email: saremi@ipm.ir
Atefeh Javadi
Affiliation:
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5531, Iran email: saremi@ipm.ir
Jacco Th. van Loon
Affiliation:
Lennard-Jones Laboratories, Keele University, ST5 5BG, UK
Habib Khosroshahi
Affiliation:
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5531, Iran email: saremi@ipm.ir
Sara Rezaei kh
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
Roya Hamedani Golshan
Affiliation:
Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
Seyed A. Hashemi
Affiliation:
School of Astronomy, Institute for Research in Fundamental Sciences (IPM), Tehran, 19395-5531, Iran email: saremi@ipm.ir Physics Department, Sharif University of Technology, Tehran 1458889694, Iran
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Abstract

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Dwarf galaxies in the Local Group (LG) represent a distinct as well as diverse family of tracers of the earliest phases of galaxy assembly and the processing resulting from galactic harrassment. Their stellar populations can be resolved and used as probes of the evolution of their host galaxy. In this regard, we present the first reconstruction of the star formation history (SFH) of them using the most evolved AGB stars that are long period variable (LPV). LPV stars trace stellar populations as young as ∼ 30 Myr to as old as the oldest globular clusters. For the nearby, relatively massive and interacting gas-rich dwarf galaxies, the Magellanic Clouds, we found that the bulk of the stars formed ∼ 10 Gyr ago for the LMC, while the strongest episode of star formation in the SMC occurred a few Gyr later. A peak in star formation around 0.7 Gyr ago in both Clouds is likely linked to their recent interaction. The Andromeda satellite pair NGC147/185 show different histories; the main epoch of star formation for NGC 185 occurred 8.3 Gyr ago, followed by a much lower, but relatively constant star formation rate (SFR). In the case of NGC 147, the SFR peaked only 6.9 Gyr ago, staying intense until ∼ 3 Gyr ago. Star formation in the isolated gas-rich dwarf galaxy IC 1613 has proceeded at a steady rate over the past 5 Gyr, without any particular dominant epoch. Due to lack of sufficient data, we have conducted an optical monitoring survey at the Isaac Newton Telescope (INT) of 55 dwarf galaxies in the LG to reconstruct the SFH of them uniformly. The observations are made over ten epochs, spaced approximately three months apart, as the luminosity of LPV stars varies on timescales of months to years. The system of galactic satellites of the large Andromeda spiral galaxy (M31) forms one of the key targets of our monitoring survey. We present the first results in the And I dwarf galaxy, where we discovered 116 LPVs among over 10,000 stars.

Keywords

stars: formationstars: AGBstars: variables: LPVGalaxy: stellar content(galaxies:) Local Groupgalaxies: dwarf
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S344: Dwarf Galaxies: From the Deep Universe to the Present , August 2018 , pp. 125 - 129
Copyright
© International Astronomical Union 2019 

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