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research article

The extended stellar halo' of the Ursa Minor dwarf galaxy

Sestito, Federico
•
Zaremba, Daria
•
Venn, Kim A.
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August 21, 2023
Monthly Notices Of The Royal Astronomical Society

Stellar candidates in the Ursa Minor (UMi) dwarf galaxy have been found using a new Bayesian algorithm applied to Gaia EDR3 data. Five of these targets are located in the extreme outskirts of UMi, from similar to 5 to 12 elliptical half-light radii (r h), where r h (UMi) = 17.32 +/- 0.11 arcmin, and have been observed with the high-resolution Gemini Remote Access to CFHT ESPaDOnS Spectrograph at the Gemini North telescope. Precise radial velocities (sRV < 2 km s-1) and metallicities (s[ Fe/H] < 0.2 dex) confirm their memberships of UMi. Detailed analysis of the brightest and outermost star (Target 1, at similar to 12r h), yields precision chemical abundances for the a(Mg, Ca, and Ti), odd-Z (Na, K, and Sc), Fe-peak (Fe, Ni, and Cr), and neutron-capture (Ba) elements. With data from the literature and APOGEE data release 17, we find the chemical patterns in UMi are consistent with an outside-in star-formation history that includes yields from core-collapse supernovae, asymptotic giant branch stars, and Type Ia supernovae. Evidence for a knee in the [a/Fe] ratios near [Fe/H] similar to-2.1 indicates a low star-formation efficiency similar to that in other dwarf galaxies. Detailed analysis of the surface number density profile shows evidence that UMi's outskirts have been populated by tidal effects, likely as a result of completing multiple orbits around the Galaxy.

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Type
research article
DOI
10.1093/mnras/stad2427
Web of Science ID

WOS:001063386300005

Author(s)
Sestito, Federico
Zaremba, Daria
Venn, Kim A.
D'Aoust, Lina
Hayes, Christian
Jensen, Jaclyn
Navarro, Julio F.
Jablonka, Pascale  
Fernandez-Alvar, Emma
Glover, Jennifer
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Date Issued

2023-08-21

Publisher

OXFORD UNIV PRESS

Published in
Monthly Notices Of The Royal Astronomical Society
Volume

525

Issue

2

Start page

2875

End page

2890

Subjects

Astronomy & Astrophysics

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stars: abundances

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stars: population ii

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galaxies: dwarf

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galaxies: evolution

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galaxies: formation

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galaxies: individual: ursa minor

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metal-poor stars

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low-metallicity stars

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lte line formation

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milky-way halo

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local group

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proper motions

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spheroidal galaxies

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formation history

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atmospheric parameters

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chemical abundances

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LASTRO  
Available on Infoscience
October 23, 2023
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/201851
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