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Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc

Drake, A. J. and Catelan, M. and Djorgovski, S. G. and Torrealba, G. and Graham, M. J. and Mahabal, A. and Prieto, J. L. and Donalek, C. and Williams, R. and Larson, S. and Christensen, E. and Beshore, E. (2013) Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc. Astrophysical Journal, 765 (2). Art. No. 154. ISSN 0004-637X. doi:10.1088/0004-637X/765/2/154.

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We present the analysis of 1207 RR Lyrae found in photometry taken by the Catalina Survey's Mount Lemmon telescope. By combining accurate distances for these stars with measurements for ~14,000 type-ab RR Lyrae from the Catalina Schmidt telescope, we reveal an extended association that reaches Galactocentric distances beyond 100 kpc and overlaps the Sagittarius stream system. This result confirms earlier evidence for the existence of an outer halo tidal stream resulting from a disrupted stellar system. By comparing the RR Lyrae source density with that expected based on halo models, we find the detection has ~8σ significance. We investigate the distances, radial velocities, metallicities, and period-amplitude distribution of the RR Lyrae. We find that both radial velocities and distances are inconsistent with current models of the Sagittarius stream. We also find tentative evidence for a division in source metallicities for the most distant sources. Following prior analyses, we compare the locations and distances of the RR Lyrae with photometrically selected candidate horizontal branch stars and find supporting evidence that this structure spans at least 60° of the sky. We investigate the prospects of an association between the stream and the unusual globular cluster NGC 2419.

Item Type:Article
Related URLs:
URLURL TypeDescription
Catelan, M.0000-0001-6003-8877
Djorgovski, S. G.0000-0002-0603-3087
Graham, M. J.0000-0002-3168-0139
Mahabal, A.0000-0003-2242-0244
Prieto, J. L.0000-0003-0943-0026
Larson, S.0000-0002-0057-8211
Additional Information:© 2013 American Astronomical Society. Received 2012 September 3; accepted 2013 January 24; published 2013 February 27. CRTS and CSDR1 are supported by the U.S. National Science Foundation under grants AST-0909182 and CNS-0540369. The CSS survey is funded by the National Aeronautics and Space Administration under Grant No. NNG05GF22G issued through the Science Mission Directorate Near-Earth Objects Observations Program. J.L.P. acknowledges support from NASA through Hubble Fellowship Grant HF-51261.01-A awarded by the STScI, which is operated by AURA, Inc., for NASA, under contract NAS 5-26555. Support for M.C. and G.T. is provided by the Ministry for the Economy, Development, and Tourism’s Programa Inicativa Científica Milenio through grant P07-021-F, awarded to The Milky Way Millennium Nucleus; by Proyecto Basal PFB- 06/2007; by Proyecto FONDECYT Regular 1110326; and by Proyecto Anillo ACT-86. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III Web site is
Funding AgencyGrant Number
NASA Hubble FellowshipHF-51261.01-A
NASANAS 5-26555
Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica MilenioP07-021-F
Proyecto BasalPFB-06/2007
Proyecto FONDECYT Regular1110326
Proyecto AnilloACT-86
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:galaxies: stellar content; Galaxy: formation; Galaxy: halo; Galaxy: stellar content; Galaxy: structure; stars: variables: RR Lyrae
Issue or Number:2
Record Number:CaltechAUTHORS:20130408-082022888
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Official Citation:Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc A. J. Drake et al. 2013 ApJ 765 154
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37797
Deposited By: Ruth Sustaita
Deposited On:08 Apr 2013 15:40
Last Modified:09 Nov 2021 23:31

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