Measuring the Gravitomagnetic Distortion from Rotating Halos. I. Methods
Abstract
Source galaxy images are distorted not only by a static gravitational potential, but also by framedragging induced by massive rotating objects like clusters of galaxies. Such an effect is well understood theoretically; it is therefore of great interest to estimate its detectability for future surveys. In this work, we analyze the lensing convergence κ around rotating dark matter halos. The rotation of the massive objects generates a gravitomagnetic potential giving rise to an anisotropic contribution to the lensing potential. We construct an estimator δκ to describe the difference between the symmetric enhancement and reduction of κ around the halo rotation axis, finding that it is well approximated by a function proportional to the halo velocity dispersion squared times a dimensionless angular momentum parameter. Using simulation mocks with realistic noise level for a survey like the Legacy Survey of Space and Time (LSST), we test our estimator, and show that the signal from framedragging of stacked rotating lenses is consistent with zero within 1σ. However, we find that the most massive cluster in SDSS DR7 spectroscopic selected group catalog has a lineofsight rotation velocity of 195.0 km s^{1} and velocity dispersion of 667.8 km s^{1}, which is at 1.2 × 10^{8} odds according to the angular momentum probability distribution inferred from Nbody simulations. By studying SDSS DR7 spectroscopic selected group catalog, we show how rotating clusters can be identified, and, finding that fast rotating clusters might be more abundant than in estimates based on simulations, a detection of gravitomagnetic distortion may be at reach in future surveys.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 2021
 DOI:
 10.3847/15384357/abe69e
 arXiv:
 arXiv:2009.12011
 Bibcode:
 2021ApJ...911...44T
 Keywords:

 Galaxy clusters;
 General relativity;
 584;
 641;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 This article has been accepted by The Astrophysical Journal