The Lensing Cluster MS 0440+0204 Seen byHST,ROSAT, andASCA. I. Cluster Properties

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Abstract
We present an analysis of the properties of the lensing cluster MS 0440+0204 at z = 0.1965. MS 0440+0204 has been observed with a variety of telescopes at diverse wavelengths: from the ground with the Canada-France-Hawaii Telescope, the Multiple Mirror Telescope, and the Keck Telescope, and from the Earth orbit with HST, ROSAT, and ASCA. Mass determinations are separately obtained from galaxy virial motions and X-ray profile fitting. A simple β model fitted to the X-ray data yields a mass of (1.3 ± 0.2) × 1014 M☉ within 583 kpc of the cluster center, but more general models fitted all of our data better and allow a wider range of masses that are consistent with the lensing data. In addition, the X-ray data yield a mass distribution profile that is well described by a β model with a core radius of 26.7 kpc. The velocity dispersion of galaxies yields a mass of 4.8+ 1.5−0.94 × 1014 M☉ within 900 kpc. In the inner 245 there are 24 arcs that appear to be strong gravitationally-lensed images of background sources. Models of the cluster mass distribution and its lensing properties reveal five background sources at various redshifts, each forming two or more arcs. We do not have a redshift for any arc with multiple images; therefore, we can only place upper and lower limits to the mass of the cluster from gravitational lensing. At 100 kpc, the lower limit mass from lensing is about a factor of 2 greater than the X-ray-determined mass. The rate of increase in the projected mass at this radius is also greater for the lens model than the X-ray determination. To reconcile the mass estimates from the X-rays and the lensing and to try to understand the steep slope of the gravitational lens mass, we tentatively explore a model with a supercluster surrounding the cluster and with a mass profile that increases more rapidly than a β model at large radii.
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