A Survey of Dark Matter in Clusters: Calibration of Weak Gravitational Lens Tomographic Mapping

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Session 23 -- Gravitational Lensing
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[23.05] A Survey of Dark Matter in Clusters: Calibration of Weak Gravitational Lens Tomographic Mapping

Tony Tyson \& Philippe Fischer (AT\&T Bell Labs)

Preliminary results for the total mass and light distribution in a survey of 28 clusters of galaxies will be given. The mass is derived from hundreds of weak lensing arclets --- gravitational lens distorted background faint blue galaxies --- found in deep CCD shift-and-stare exposures to uniform faint surface brightness (29 mag arcsec$^2$) in two colors. Gravitational lens distortion tomography (arclet inversion) is a direct measure of the projected total mass distribution in the lens. In this poster we focus on the mass calibration of this cluster survey.

Realistic Monte Carlo simulations of the entire source-lens-atmosphere-detector process were performed, including multiple background galaxy redshift shells, masses for individual cluster galaxies, clumped dark matter, atmospheric seeing, and pixel sampling and sky shot noise. These allow us to verify analytic corrections for systematics in the mass profiles at large radius from the cluster center arising from the image ellipticity measurement, arclet inversion, and finite image resolution. "Blank" field HST WFC-2 Medium Deep Survey data, together with seeing deconvolved ground-based data, are used to derive the source galaxy angular scales. Given accurate seeing and source galaxy angular scales, we find that the mass scale may be calibrated from these weak lensing data alone. Strong lensing (long arcs at the Einstein critical radius) then forms an independent check on this weak lensing mass scale calibration.

We will show a color video of Monte Carlo simulations of lensing in the rich cluster Abell 1689 in which 5 background color-encoded redshift shells of source galaxies are scanned past the cluster. The rate of formation of strong lensing artifacts such as radial spikes and rings can be a useful test of the underlying mass profile.

Monday program listing