Constraint on the post-Newtonian parameter {gamma} on galactic size scales
- Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138 (United States)
- Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)
We constrain the post-Newtonian gravity parameter {gamma} on kiloparsec scales by comparing the masses of 15 elliptical lensing galaxies from the Sloan Lens ACS Survey as determined in two independent ways. The first method assumes only that Newtonian gravity is correct and is independent of {gamma}, while the second uses gravitational lensing which depends on {gamma}. More specifically, we combine Einstein radii and radial surface-brightness gradient measurements of the lens galaxies with empirical distributions for the mass concentration and velocity anisotropy of elliptical galaxies in the local universe to predict {gamma}-dependent probability distributions for the lens-galaxy velocity dispersions. By comparing with observed velocity dispersions, we derive a maximum-likelihood value of {gamma}=0.98{+-}0.07 (68% confidence). This result is in excellent agreement with the prediction of general relativity that {gamma}=1, which has previously been verified to this accuracy only on solar-system length scales.
- OSTI ID:
- 20871162
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 74, Issue 6; Other Information: DOI: 10.1103/PhysRevD.74.061501; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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