The external shear in the gravitationally lensed system Q 2237+0305: A two-plane lens modelling

Bm. Mihov, The external shear in the gravitationally lensed system Q 2237+0305: A two-plane lens modelling, ASTRON ASTR, 370(1), 2001, pp. 43-52
Citations number
Categorie Soggetti
Space Sciences
Journal title
ISSN journal
0004-6361 → ACNP
Year of publication
43 - 52
SICI code
We present one-plane lens models (with and without an external shear added) and a two-plane lens model for the gravitationally lensed system Q 2237+03 05. The first (the main) lens plane is at z = 0.0394 and the second lens pl ane is at z = 0.5664. We found the best lens solutions for this system up t o now - chi (2)(df) = 0.35 for the external shear model and chi (2)(df) = 0 .44 for the two-plane model. Generally, we found a nearly singular (with an upper limit on the core radius of approximate to 36 pc) pseudoisothermal m ass distribution for the central part of the main lens that is consistent w ith the available observations of the Q 2237+0305 system (except the misali gnment of about 13 degrees between the mass and the light distributions). F urthermore, the main source of the external shear is possibly the object co nnected with the MgII absorption. In any case the external perturbations sh ould be taken into account in the future models of the gravitationally lens ed system Q 2237+0305. For the two-plane lens model the blue mass-to-light ratio for the central 1" of the SBb galaxy-lens is estimated to be 6.8(-0.1 )(+0.3) M-circle dot/L-circle dot,B, and the mass of the SBb galaxy inside the mean ring of the images is M(less than or equal to 0".885) = 1.471(-0.0 10)(+0.069) 10(10) M-circle dot. The introduction of the second lens plane leaves the core radius, the axis ratio and the position angle of the mass d istribution in the main lens almost unchanged but decreases the mass inside the mean ring of the images with 1.2% and increases the total magnificatio n of the images by a factor of approximate to1.5. The parameters of the mas s distribution in the second lens are not very well constrained. If the sec ond lens is a single galaxy we set a lower limit on the radius of the MgII absorbing halo of approximate to 14 kpc. The probability for the two-plane lens model is estimated to be 8.0 10(-9).