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Exploring the Variable Sky with LINEAR. II. Halo Structure and Substructure Traced by RR Lyrae Stars to 30 kpc

Sesar, Branimir and Ivezić, Željko and Stuart, J. Scott and Morgan, Dylan M. and Becker, Andrew C. and Sharma, Sanjib and Palaversa, Lovro and Jurić, Mario and Wozniak, Przemysław and Oluseyi, Hakeem (2013) Exploring the Variable Sky with LINEAR. II. Halo Structure and Substructure Traced by RR Lyrae Stars to 30 kpc. Astronomical Journal, 146 (2). Art. No. 21. ISSN 0004-6256. doi:10.1088/0004-6256/146/2/21.

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We present a sample of ~5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over ~8000 deg^2 of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of ~4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, with the ratio of the type II and I subsamples of about 1:4, but with a weaker separation than for globular cluster stars. The wide sky coverage and depth of this sample allow unique constraints for the number density distribution of halo RRab stars as a function of galactocentric distance: it can be described as an oblate ellipsoid with an axis ratio q = 0.63 and with either a single or a double power law with a power-law index in the range –2 to –3. Consistent with previous studies, we find that the Oosterhoff type II subsample has a steeper number density profile than the Oosterhoff type I subsample. Using the group-finding algorithm EnLink, we detected seven candidate halo groups, only one of which is statistically spurious. Three of these groups are near globular clusters (M53/NGC 5053, M3, M13), and one is near a known halo substructure (Virgo Stellar Stream); the remaining three groups do not seem to be near any known halo substructures or globular clusters and seem to have a higher ratio of Oosterhoff type II to Oosterhoff type I RRab stars than what is found in the halo. The extended morphology and the position (outside the tidal radius) of some of the groups near globular clusters are suggestive of tidal streams possibly originating from globular clusters. Spectroscopic follow-up of detected halo groups is encouraged.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle Paper
Sesar, Branimir0000-0002-0834-3978
Ivezić, Željko0000-0001-5250-2633
Sharma, Sanjib0000-0002-0920-809X
Jurić, Mario0000-0003-1996-9252
Wozniak, Przemysław0000-0002-9919-3310
Additional Information:© 2013 The American Astronomical Society. Received 2013 February 3; accepted 2013 May 8; published 2013 June 27. B.S. is grateful for NSF grant AST-0908139 to Judith G. Cohen for partial support. Ž.I. acknowledges support by NSF grants AST-0707901 and AST-1008784 to the University of Washington, by NSF grant AST-0551161 to LSST for design and development activity, and by the Croatian National Science Foundation grant O-1548-2009. A.C.B. acknowledges support from NASA ADP grant NNX09AC77G. The LINEAR program is funded by the National Aeronautics and Space Administration at MIT Lincoln Laboratory under Air Force Contract FA8721- 05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government.
Funding AgencyGrant Number
Croatian National Science FoundationO-1548-2009
Air ForceFA8721-05-C-0002
Subject Keywords:Galaxy: halo – Galaxy: stellar content – Galaxy: structure – stars: variables: RR Lyrae Online-only material: animation, color figures, machine-readable and VO tables, supplemental data (FITS) file (tar.gz)
Issue or Number:2
Record Number:CaltechAUTHORS:20130918-080539838
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Official Citation:Exploring the Variable Sky with LINEAR. II. Halo Structure and Substructure Traced by RR Lyrae Stars to 30 kpc Branimir Sesar et al. 2013 The Astronomical Journal 146 21
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41374
Deposited By: Tony Diaz
Deposited On:18 Sep 2013 17:11
Last Modified:10 Nov 2021 04:29

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