The Pristine dwarf galaxy survey – IV. Probing the outskirts of the dwarf galaxy Boötes&nbsp;I

Longeard, Nicolas; Jablonka, Pascale; Arentsen, Anke; Thomas, Guillaume F.; Aguado, David S.; Carlberg, Raymond G.; Lucchesi, Romain; Malhan, Khyati; Martin, Nicolas; McConnachie, Alan W.; Navarro, Julio F.; Sánchez-Janssen, Rubén; Sestito, Federico; Starkenburg, Else; Yuan, Zhen

doi:10.1093/mnras/stac1827

The Pristine dwarf galaxy survey – IV. Probing the outskirts of the dwarf galaxy Boötes I

Journal Article · Tue Jul 05 00:00:00 EDT 2022 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stac1827· OSTI ID:1886702

Longeard, Nicolas; Jablonka, Pascale; ; Thomas, Guillaume F.; Aguado, David S.; Carlberg, Raymond G.; ; Malhan, Khyati; ; McConnachie, Alan W.; Navarro, Julio F.; ; ; Starkenburg, Else;

ABSTRACT

We present a new spectroscopic study of the dwarf galaxy Boötes I (Boo I) with data from the Anglo-Australian Telescope and its AAOmega spectrograph together with the Two Degree Field multi-object system. We observed 36 high-probability Boo I stars selected using Gaia Early Data Release 3 proper motions and photometric metallicities from the Pristine survey. Out of those, 27 are found to be Boo I stars, resulting in an excellent success rate of 75 per cent at finding new members. Our analysis uses a new pipeline developed to estimate radial velocities and equivalent widths of the calcium triplet lines from Gaussian and Voigt line profile fits. The metallicities of 16 members are derived, including 3 extremely metal-poor stars ([Fe/H] < −3.0), which translates into a success rate of 25 per cent at finding them with the combination of Pristine and Gaia. Using the large spatial extent of our new members that spans up to 4.1 half-light radii and spectroscopy from the literature, we find a systemic velocity gradient of 0.40 ± 0.10 km s−1 arcmin−1 and a small but resolved metallicity gradient of −0.008 ± 0.003 dex arcmin−1. Finally, we show that Boo I is more elongated than previously thought with an ellipticity of ϵ = 0.68 ± 0.15. Its velocity and metallicity gradients as well as its elongation suggest that Boo I may have been affected by tides, a result supported by direct dynamical modelling.

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Sponsoring Organization:: USDOE

OSTI ID:: 1886702

Journal Information:: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 2 Vol. 516; ISSN 0035-8711

Publisher:: Oxford University PressCopyright Statement

Country of Publication:: United Kingdom

Language:: English

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