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Chemical abundances in the nucleus of the Sagittarius dwarf spheroidal galaxy

Abstract : We present iron, magnesium, calcium, and titanium abundances for 235 stars in the central region of the Sagittarius dwarf spheroidal galaxy (within 9.0' ≃ 70 pc from the centre) from medium-resolution Keck/Deep Imaging Multi-Object Spectrograph spectra. All the considered stars belong to the massive globular cluster M 54 or to the central nucleus of the galaxy (Sgr, N). In particular we provide abundances for 109 stars with [Fe/H] ≥-1.0, more than doubling the available sample of spectroscopic metallicity and α-elements abundance estimates for Sgr dSph stars in this metallicity regime. We find for the first time a metallicity gradient in the Sgr, N population, whose peak iron abundance goes from [Fe/H] =-0.38 for R ≤ 2.5' to [Fe/H] =-0.57 for 5.0 DM = 6 × 1010M) and a significant event of mass-stripping occurred a few Gyr ago, presumably starting at the first peri-Galactic passage after infall.

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Submitted on : Wednesday, June 29, 2022 - 12:08:36 PM
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A. Mucciarelli, M. Bellazzini, R. Ibata, D. Romano, S. C. Chapman, et al.. Chemical abundances in the nucleus of the Sagittarius dwarf spheroidal galaxy. Astronomy and Astrophysics - A&A, EDP Sciences, 2017, 605, ⟨10.1051/0004-6361/201730707⟩. ⟨insu-03707875⟩



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