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New views of the distant stellar halo

Sanderson, Robyn E. and Secunda, Amy and Johnston, Kathryn V. and Bochanski, John J. (2017) New views of the distant stellar halo. Monthly Notices of the Royal Astronomical Society, 470 (4). pp. 5014-5031. ISSN 0035-8711.

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Currently, only a small number of Milky Way (MW) stars are known to exist beyond 100 kpc from the Galactic Centre. Though the distribution of these stars in the outer halo is believed to be sparse, they can provide evidence of more recent accretion events than in the inner halo and help map out the MW's dark matter halo to its virial radius. We have re-examined the outermost regions of 11 existing stellar halo models with two synthetic surveys: one mimicking present-day searches for distant M giants and another mimicking RR Lyra (RRL) projections for the Large Synoptic Survey Telescope (LSST). Our models suggest that colour and proper motion cuts currently used to select M giant candidates for follow-up successfully remove nearly all self-contamination from foreground halo dwarf stars and are useful for focusing observations on distant M giants, of which there are thousands to tens of thousands beyond 100 kpc in our models. We likewise expect that LSST will identify comparable numbers of RRLe at these distances. We demonstrate that several observable properties of both tracers, such as proximity of neighbouring stars, proper motions and distances (for RRLe), could help us separate different accreted dwarf galaxies from one another in the distant MW halo. We also discuss prospects for using ratios of M giants to RRLe as a proxy for accretion time, which in the future could provide new constraints on the recent accretion history of our Galaxy.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sanderson, Robyn E.0000-0003-3939-3297
Johnston, Kathryn V.0000-0001-6244-6727
Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Received: 20 September 2016. Revision Received: 22 June 2017. Accepted: 22 June 2017. Published: 27 June 2017. RES is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under grant AST-1400989. AS contributions were also partially supported by AST-1400989. KVJ and AS contributions were enabled by NSF grant AST-1312196. JJB acknowledges support from NSF CAREER grant AST-1151462.
Funding AgencyGrant Number
NSF Astronomy and Astrophysics FellowshipAST-1400989
Subject Keywords:stars: variables: RR Lyrae – Galaxy: formation – Galaxy: halo – Galaxy: kinematics and dynamics – Galaxy: stellar content – Galaxy: structure.
Issue or Number:4
Record Number:CaltechAUTHORS:20170918-074411692
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Official Citation:Robyn E. Sanderson, Amy Secunda, Kathryn V. Johnston, John J. Bochanski; New views of the distant stellar halo, Monthly Notices of the Royal Astronomical Society, Volume 470, Issue 4, 1 October 2017, Pages 5014–5031,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81510
Deposited By: Ruth Sustaita
Deposited On:18 Sep 2017 21:07
Last Modified:06 Feb 2020 23:44

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