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The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy

Abstract : We present a comprehensive metallicity analysis of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) using Pristine CaHK photometry. We base our member selection on Gaia EDR3 astrometry applying a magnitude limit at G0 = 17.3, and our population study on the metallicity-sensitive photometry from the Pristine Inner Galaxy Survey (PIGS). Working with photometric metallicities instead of spectroscopic metallicities allows us to cover an unprecedented large area (~100 square degrees) of the dwarf galaxy, and to study the spatial distribution of its members as function of metallicity with little selection effects. Our study compares the spatial distributions of a metal-poor population of 9719 stars with [Fe/H] <-1.3 and a metal rich one of 30115 stars with [Fe/H] >-1.0. The photometric Sgr sample also allows us to assemble the largest sample of 1150 very metal-poor Sgr candidates ([Fe/H] <-2.0). By investigating and fitting the spatial properties of the metal-rich and metal-poor population, we find a negative metallicity gradient which extends up to 12 degrees from the Sgr center (or ~5.5 kpc at the distance of Sgr), the limit of our footprint. We conclude that the relative number of metal-poor stars increases in the outer areas of the galaxy, while the central region is dominated by metal-rich stars. These finding suggest an outside-in formation process and are an indication of the extended formation history of Sgr, which has been affected by the tidal interaction between Sgr and the Milky Way.
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https://hal-insu.archives-ouvertes.fr/insu-03820720
Contributor : Olivier Hauss Connect in order to contact the contributor
Submitted on : Wednesday, October 19, 2022 - 11:22:43 AM
Last modification on : Thursday, November 24, 2022 - 5:02:58 PM

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Sara Vitali, Anke Arentsen, Else Starkenburg, Paula Jofré, Nicolas F. Martin, et al.. The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy. Monthly Notices of the Royal Astronomical Society, 2022, ⟨10.1093/mnras/stac2869⟩. ⟨insu-03820720⟩

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