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A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies

Collins, Michelle L M, Tollerud, Erik J, Rich, R Michael, Ibata, Rodrigo A, Martin, Nicolas F, Chapman, Scott C, Gilbert, Karoline M and Preston, Janet (2019) A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies Monthly Notices of the Royal Astronomical Society, stz3252.

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Abstract

With a central surface brightness of μ0 = 29.3 mag. per sq. arcsec, and half-light radius of rhalf=3.1+0.9−1.1kpc, Andromeda XIX (And XIX) is an extremely diffuse satellite of Andromeda. We present spectra for ∼100 red giant branch stars in this galaxy, plus 16 stars in a nearby stellar stream. With this exquisite dataset, we re-derive the properties of And XIX, measuring a systemic velocity of ˂vr˃ = − 109.0 ± 1.6 kms−1 and a velocity dispersion of σvr=7.8+1.7−1.5σvr=7.8+1.7−1.5 kms−1(higher than derived in our previous work). We marginally detect a velocity gradient along the major axis of dvdχ=−2.1±1.8 kms−1dvdχ=−2.1±1.8 kms−1kpc−1. We find its mass-to-light ratio is higher than galaxies of comparable stellar mass (⁠[M/L]half=278+146−198M⊙/L⊙), but its dynamics place it in a halo with a similar total mass to these galaxies. This could suggest that And XIX is a “puffed up” dwarf galaxy, whose properties have been altered by tidal processes, similar to its Milky Way counterpart, Antlia II. For the nearby stream, we measure vr = −279.2 ± 3.7 kms−1, and σv=13.8+3.5−2.6 kms−1. We measure its metallicity, and find it to be more metal rich than And XIX, implying that the two features are unrelated. Finally, And XIX’s dynamical and structural properties imply it is a local analogue to ultra diffuse galaxies (UDGs). Its complex dynamics suggest that the masses of distant UDGs measured from velocity dispersions alone should be carefully interpreted.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Collins, Michelle L Mm.collins@surrey.ac.uk
Tollerud, Erik J
Rich, R Michael
Ibata, Rodrigo A
Martin, Nicolas F
Chapman, Scott C
Gilbert, Karoline M
Preston, Janetj.preston@surrey.ac.uk
Date : 21 November 2019
DOI : 10.1093/mnras/stz3252
Copyright Disclaimer : © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record - Michelle L M Collins, Erik J Tollerud, R Michael Rich, Rodrigo A Ibata, Nicolas F Martin, Scott C Chapman, Karoline M Gilbert, Janet Preston, 'A detailed study of Andromeda XIX, an extreme local analogue of ultra diffuse galaxies', Monthly Notices of the Royal Astronomical Society, stz3252 - is available online at: https://doi.org/10.1093/mnras/stz3252.
Uncontrolled Keywords : Stars: kinematics and dynamics. Galaxies: dwarf.
Depositing User : Clive Harris
Date Deposited : 27 Nov 2019 10:28
Last Modified : 27 Nov 2019 12:40
URI: http://epubs.surrey.ac.uk/id/eprint/853204

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