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Article Dans Une Revue The Astrophysical Journal Année : 2024

Stellar Metallicities and Gradients in the Isolated, Quenched Low-mass Galaxy Tucana

Sal Wanying Fu
  • Fonction : Auteur
Daniel R. Weisz
  • Fonction : Auteur
Else Starkenburg
  • Fonction : Auteur
Francisco J. Mercado
  • Fonction : Auteur
Alessandro Savino
  • Fonction : Auteur
Michael Boylan-Kolchin
  • Fonction : Auteur
Patrick Côté
  • Fonction : Auteur
Andrew E. Dolphin
  • Fonction : Auteur
Nicolas Longeard
  • Fonction : Auteur
Mario L. Mateo
  • Fonction : Auteur
Jenna Samuel
  • Fonction : Auteur
Nathan R. Sandford
  • Fonction : Auteur

Résumé

We measure the metallicities of 374 red giant branch (RGB) stars in the isolated, quenched dwarf galaxy Tucana using Hubble Space Telescope narrowband (F395N) calcium H and K imaging. Our sample is a factor of ∼7 larger than what is available from previous studies. Our main findings are as follows. (i) A global metallicity distribution function (MDF) with $\langle {\rm{[Fe/H]}}\rangle =-{1.55}_{-0.04}^{+0.04}$ and ${\sigma }_{{\rm{[Fe/H]}}}={0.54}_{-0.03}^{+0.03}$ . (ii) A metallicity gradient of ‑0.54 ± 0.07 dex ${R}_{e}^{-1}$ (‑2.1 ± 0.3 dex kpc‑1) over the extent of our imaging (∼2.5 R e ), which is steeper than literature measurements. Our finding is consistent with predicted gradients from the publicly available FIRE-2 simulations, in which bursty star formation creates stellar population gradients and dark matter cores. (iii) Tucana's bifurcated RGB has distinct metallicities: a blue RGB with $\langle {\rm{[Fe/H]}}\rangle =-{1.78}_{-0.06}^{+0.06}$ and ${\sigma }_{{\rm{[Fe/H]}}}={0.44}_{-0.06}^{+0.07}$ and a red RGB with $\langle {\rm{[Fe/H]}}\rangle =-{1.08}_{-0.07}^{+0.07}$ and ${\sigma }_{{\rm{[Fe/H]}}}={0.42}_{-0.06}^{+0.06}$ . (iv) At fixed stellar mass, Tucana is more metal-rich than Milky Way satellites by ∼0.4 dex, but its blue RGB is chemically comparable to the satellites. Tucana's MDF appears consistent with star-forming isolated dwarfs, though MDFs of the latter are not as well populated. (v) About 2% of Tucana's stars have [Fe/H] < ‑3% and 20% have [Fe/H] > ‑1. We provide a catalog for community spectroscopic follow-up.
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insu-04539113 , version 1 (11-04-2024)

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Sal Wanying Fu, Daniel R. Weisz, Else Starkenburg, Nicolas Martin, Francisco J. Mercado, et al.. Stellar Metallicities and Gradients in the Isolated, Quenched Low-mass Galaxy Tucana. The Astrophysical Journal, 2024, 965, ⟨10.3847/1538-4357/ad25ed⟩. ⟨insu-04539113⟩
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