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Quasar microlensing and dark matterThe amplification of quasar brightness due to gravitational lensing by foreground objects is discussed. It is shown that a recently published sample of X-ray-selected quasars behind foreground galaxies shows a statistically significant brightening compared to a control sample. Correlations with galaxy redshift and impact parameter predicted by microlensing are also demonstrated. A technique is described to measure the mean density of the lenses from a small number of identified cases of microlensing. It is shown that, in this sample, amplification bias is important in determining the mean intensity enhancement and must be included in the density estimate. Assuming that at least two of the four intrinsically brightest quasars behind galaxies are indeed microlensed, the present data yield a formal lower limit on the mean density parameter of lenses Omega(l) greater than 0.25 at 95 percent confidence. These data also imply that a considerable quantity of dark matter exists in macroscopic objects outside the visible parts of galaxies but is still highly correlated with them.
Document ID
19880063968
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Rix, Hans-Walter
(Arizona Univ. Tucson, AZ, United States)
Hogan, Craig J.
(Steward Observatory Tucson, AZ, United States)
Date Acquired
August 13, 2013
Publication Date
September 1, 1988
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 332
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
88A51195
Funding Number(s)
CONTRACT_GRANT: NAGW-763
Distribution Limits
Public
Copyright
Other

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