Chandra Observations of the Gravitationally Lensed System 2016 + 112

An observation of the gravitationally lensed system 2016+112 with the Chandra X-ray Observatory has resolved a mystery regarding the proposed presence of a dark matter object in the lens plane of this system. The Chandra ACIS observation has clearly detected the lensed images of 2016+112 with positions in good agreement with those reported in the optical and also detects 13 additional X-ray sources within a radius of 3.5 arcmin. Previous X-ray observations in the direction of 2016+112 with the ROSAT HRI and ASCA SIS have interpreted the X-ray data as arising from extended emission from a dark cluster. However, the present Chandra observation can account for all the X-ray emission as originating from the lensed images and additional point X-ray sources in the field. Thus cluster parameters based on previous X-ray observations are unreliable. We place a 3σ upper limit on the 2-10keV flux and luminosity of the cluster of 1.6 × 10 −14 erg s −1 cm −2 and 1.7 × 10 44 erg s −1 , respectively. We estimate an upper limit on the mass-to-light ratio within a radius of 800 h 50 −1 kpc of M /L V < 190 h 50 (M/L V) ⊙. None of the additional point X-ray sources are associated with the galaxy cluster members recently detected in deep optical and IR observations (Soucail et al. 2000). The lensed object is quite unusual, with reported narrow emission lines in the optical that suggest it may be a type-2 quasar (Yamada et. al. 1999). Our modeling of the X-ray spectrum of the lensed object implies that the column density of an intrinsic absorber must lie between 3 and 85 × 10 22 cm −2 (3σ confidence level). The 2-10 keV luminosity of the lensed object, corrected for the lens magnification effect and using the above range of intrinsic absorption, is 3 × 10 43-1.4 × 10 44 erg s −1. 1. INTRODUCTION Wide-separation bona fide gravitational lens (GL) systems with spectroscopically confirmed lens red-shifts have been found to contain, in many cases, galaxy-cluster or galaxy-group lenses. The presence of such massive deflectors contributes significantly to the large deflection angles observed in these systems. Solid cases of wide image separation systems containing galaxy cluster lenses are RXJ0911+0551 2016+112 also falls in the category of confirmed wide-separation GL systems and was first identified by Lawrence et al. (1984) to be comprised of at least three lensed …