We report the detection of the lens cluster of the gravitational lens ( GL ) system Q0957+561 from a deep observation with the Advanced CCD Imaging Spectrometer on-board the Chandra X-ray Observatory .
Intracluster X-ray emission is found to be centered 4 ^ { \prime \prime } . 3 _ { -1.3 } ^ { +1.3 } east and 3 ^ { \prime \prime } . 5 _ { -0.6 } ^ { +1.2 } north of image B , nearer than previous estimates .
Its spectrum can be modeled well with a thermal plasma model consistent with the emission originating from a cluster at a redshift of 0.36 .
Our best-fit estimates of the cluster temperature of T _ { e } = 2.09 _ { -0.54 } ^ { +0.83 } keV ( 90 % confidence ) and mass distribution of the cluster are used to derive the convergence parameter \kappa , the ratio of the cluster surface mass density to the critical density required for lensing .
We estimate the convergence parameter at the location of the lensed images A and B to be { \kappa _ { A } } = 0.22 ^ { +0.14 } _ { -0.07 } and { \kappa _ { B } } = 0.21 ^ { +0.12 } _ { -0.07 } , respectively ( 90 % confidence levels ) .
The observed cluster center , mass distribution and convergence parameter \kappa provide additional constraints to lens models of this system .
Our new results break a mass-sheet degeneracy in GL models of this system and provide better constraints of \sim 29 % ( 90 % confidence levels ) on the Hubble constant .
We also present results from the detection of the most distant X-ray jet ( z = 1.41 ) detected to date .
The jet extends approximately 8″ NE of image A and three knots are resolved along the X-ray jet with flux densities decreasing with distance from the core .
The observed radio and optical flux densities of the knots are fitted well with a synchrotron model and the X-ray emission is modeled well with inverse Compton scattering of Cosmic Microwave Background photons by synchrotron-emitting electrons in the jet .