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Stellar chemo-kinematics of isolated dwarf galaxies
Salvatore Taibi (Instituto de Astrofisica de Canarias)
Tuesday 25/06/2019 @ 14:00, Sala IV piano Battiferro
Thanks to their vicinity, the internal kinematic and chemical properties of Local Group (LG) dwarf galaxies can be studied in great detail from their resolved stars. This makes of these systems a perfect laboratory to understand galaxy evolution and test LCDM predictions on the smallest galactic scales. However the majority of dwarf galaxies in the LG are found to be satellites of the Milky Way or M31, thus it is hard to constrain if their present-day observed properties are mainly caused by internal or environmental mechanisms. To minimize the role of the environment and gain insights into their intrinsic properties, we focused on a sample of 4 isolated dwarfs in the LG: the two early-type Cetus and Tucana, and the two late-type Aquarius and Phoenix. To this end we have obtained line-of-sight velocities and metallicities ([Fe/H]) for sizable numbers (~50-200) of individual red giant branch stars per galaxy from VLT/FORS2 MXU spectroscopic observations in the region of the near-IR CaII triplet. The spatially extended coverage of our data allowed us to obtain information on the wide-area kinematical and chemical properties of these objects. In this talk I will present the main results of the analysis we conducted on these dwarf galaxies. In particular, Cetus and Tucana resulted to be pressure supported systems with little to no significant signs of internal rotation, like their MW-satellite counterparts; on the other hand, the study of Aquarius and Phoenix showed an unexpected kinematic behaviour of their stellar component that may be related to recent merger events. All 4 galaxies show radial metallicity gradients, independently of their morphology or internal kinematic status. Since metallicity gradients have been observed in other similarly luminous systems inhabiting very different environments, this may hint that they are being driven by internal mechanisms.