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Published January 20, 2013 | Published
Journal Article Open

Probing the Outer Galactic Halo with RR Lyrae from the Catalina Surveys


We present analysis of 12,227 type-ab RR Lyraes (RRLs) found among the 200 million public light curves in Catalina Surveys Data Release 1. These stars span the largest volume of the Milky Way ever surveyed with RRLs, covering ~20,000 deg2 of the sky (0° < α < 360°, –22° < δ < 65°) to heliocentric distances of up to 60 kpc. Each of the RRLs is observed between 60 and 419 times over a six-year period. Using period finding and Fourier fitting techniques we determine periods and apparent magnitudes for each source. We find that the periods are generally accurate to σ = 0.002% in comparison to 2842 previously known RRLs and 100 RRLs observed in overlapping survey fields. We photometrically calibrate the light curves using 445 Landolt standard stars and show that the resulting magnitudes are accurate to ~0.05 mag using Sloan Digital Sky Survey (SDSS) data for ~1000 blue horizontal branch stars and 7788 RRLs. By combining Catalina photometry with SDSS spectroscopy, we analyze the radial velocity and metallicity distributions for >1500 of the RRLs. Using the accurate distances derived for the RRLs, we show the paths of the Sagittarius tidal streams crossing the sky at heliocentric distances from 20 to 60 kpc. By selecting samples of Galactic halo RRLs, we compare their velocity, metallicity, and distance with predictions from a recent detailed N-body model of the Sagittarius system. We find that there are some significant differences between the distances and structures predicted and our observations.

Additional Information

© 2013 American Astronomical Society. Received 2012 August 22; accepted 2012 November 9; published 2013 January 2. CRTS and CSDR1 are supported by the U.S. National Science Foundation under grants AST-0909182 and CNS-0540369. The work at Caltech was supported in part by the NASA Fermi grant 08-FERMI08-0025 and by the Ajax Foundation. 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 http://www.sdss3.org/. This research has made use of the International Variable Star Index (VSX) database, operated at AAVSO, Cambridge, MA, USA.

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