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A Dwarf Disrupting - Andromeda XXVII and the North West Stream

Preston, Janet, Collins, Michelle L M, Ibata, Rodrigo A, Tollerud, Erik J, Rich, R Michael, Bonaca, Ana, McConnachie, Alan W, Mackey, Dougal, Lewis, Geraint F, Martin, Nicolas F , Peñarrubia, Jorge, Chapman, Scott C and Delorme, Maxime (2019) A Dwarf Disrupting - Andromeda XXVII and the North West Stream Monthly Notices of the Royal Astronomical Society.

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We present a kinematic and spectroscopic analysis of 38 red giant branch stars, in 7 fields, spanning the dwarf spheroidal galaxy Andromeda XXVII and the upper segment of the North West Stream. Both features are located in the outer halo of the Andromeda galaxy at a projected radius of 50-80 kpc, with the stream extending for ∼3° on the sky. Our data is obtained as part of the PAndAS survey and enables us to confirm that Andromeda XXVII’s heliocentric distance is 827 ± 47 kpc and spectroscopic metallicity is -2.1<sup>+0.4</sup><sub>−0.5</sub>⁠. We also re-derive Andromeda XXVII’s kinematic properties, measuring a systemic velocity = -526.1<sup>+10.0</sup><sub>−11.0</sup> kms−1 and a velocity dispersion that we find to be non-Gaussian but for which we derive a formal value of 27.0<sup>+2.2</sup><sub>−3.9</sub> kms<sup>−1</sup>. In the upper segment of the North West Stream we measure mean values for the metallicity = -1.8±0.4, systemic velocity = -519.4 ±4.0 kms<sup>−1</sup> and velocity dispersion = 10.0±4.0 kms<sup>−1</sup>. We also detect a velocity gradient of 1.7±0.3 kms<sup>−1</sup> kpc<sup>−1</sup> on an infall trajectory towards M31. With a similar gradient, acting in the same direction, in the lower segment we suggest that the North West Stream is not a single structure. As the properties of the upper segment of the North West Stream and Andromeda XXVII are consistent within 90% confidence limits, it is likely that the two are related and plausible that Andromeda XXVII is the progenitor of this stream.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Collins, Michelle L
Ibata, Rodrigo A
Tollerud, Erik J
Rich, R Michael
Bonaca, Ana
McConnachie, Alan W
Mackey, Dougal
Lewis, Geraint F
Martin, Nicolas F
Peñarrubia, Jorge
Chapman, Scott C
Date : 12 September 2019
DOI : 10.1093/mnras/stz2529
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 (
Uncontrolled Keywords : Galaxies: dwarf. Galaxies: fundamental parameters. Galaxies: kinematics and dynamics. Local Group
Depositing User : Clive Harris
Date Deposited : 30 Sep 2019 15:26
Last Modified : 30 Sep 2019 15:26

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