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First Space-Based Microlens Parallax Measurement: Spitzer Observations of OGLE-2005-SMC-001

Dong, Subo and Udalski, A. and Gould, A. and Reach, W. T. and Christie, G. W. and Boden, A. F. and Bennett, D. P. and Fazio, G. and Griest, K. and Szymański, M. K. and Kubiak, M. and Soszyński, I. and Pietrzyński, G. and Szewczyk, O. and Wyrzykowski, Ł. and Ulaczyk, K. and Wieckowski, T. and Paczyński, B. and DePoy, D. L. and Pogge, R. W. and Preston, G. W. and Thompson, I. B. and Patten, B. M. (2007) First Space-Based Microlens Parallax Measurement: Spitzer Observations of OGLE-2005-SMC-001. Astrophysical Journal, 664 (2). pp. 862-878. ISSN 0004-637X. doi:10.1086/518536.

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We combine Spitzer and ground-based observations to measure the microlens parallax of OGLE-2005-SMC-001, the first such space-based determination since S. Refsdal proposed the idea in 1966. The parallax measurement yields a projected velocity ν(over tilde) ~ 230 km s^(-1), the typical value expected for halo lenses, but an order of magnitude smaller than would be expected for lenses lying in the Small Magellanic Cloud itself. The lens is a weak (i.e., non-caustic-crossing) binary, which complicates the analysis considerably but ultimately contributes additional constraints. Using a test proposed by Assef and coworkers, which makes use only of kinematic information about different populations but does not make any assumptions about their respective mass functions, we find that the likelihood ratio is L_(halo)/L(SMC) = 20. Hence, halo lenses are strongly favored, but Small Magellanic Cloud (SMC) lenses are not definitively ruled out. Similar Spitzer observations of additional lenses toward the Magellanic Clouds would clarify the nature of the lens population. The Space Interferometry Mission could make even more constraining measurements.

Item Type:Article
Related URLs:
URLURL TypeDescription
Udalski, A.0000-0001-5207-5619
Reach, W. T.0000-0001-8362-4094
Bennett, D. P.0000-0001-8043-8413
Fazio, G.0000-0002-0670-0708
Ulaczyk, K.0000-0001-6364-408X
Pogge, R. W.0000-0003-1435-3053
Additional Information:© 2007 American Astronomical Society. Received 2007 February 11; accepted 2007 March 23. We thank Scott Gaudi for a careful reading of the manuscript, which led to many useful suggestions. We are also grateful to Patrick Tisserand for his comments. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through contract 1277721 issued by JPL/Caltech. Support for program 10544 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. S. D. and A. G. were supported in part by grant AST 04- 2758 from the NSF. Support for OGLE was provided by Polish MNiSW grant N20303032/4275, NSF grant AST 06-07070, and NASA grant NNG 06-GE27G. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. We thank the Ohio Supercomputer Center for the use of a Cluster Ohio Beowulf cluster in conducting this research.
Funding AgencyGrant Number
NASANAS 5-26555
NSFAST 04-2758
Ministerstwo Nauki i Szkolnictwa Wyższego (MNiSW)N20303032/4275
NSFAST 06-07070
Subject Keywords:dark matter; galaxies: stellar content; gravitational lensing
Issue or Number:2
Record Number:CaltechAUTHORS:20100422-095230185
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Official Citation:Subo Dong et al 2007 ApJ 664 862 doi: 10.1086/518536
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18048
Deposited By: Jason Perez
Deposited On:22 Apr 2010 18:13
Last Modified:08 Nov 2021 23:41

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