Central Image Mapping of Two-Image Strong Gravitational Lens System CLASS B2319+051

Abstract

The central image is a third image of a two-image gravitational lens system which is much fainter than the other two images, located close to the centre of the lensing galaxy. The flux density of the central image can be used to study the mass distribution of the inner part of the lensing galaxy. We present the e-MERLIN 5 GHz observation of the two-image lens system B2319+051 (zl = 0.62) (Rusin et al. 2001). The rms noise level of the observation after our self-calibration is down to 14.6 $\mu$Jy/beam which is 4.8 times lower than the image for B2319+051 first found (Rusin et al. 2001). No central image is detected in B2319+051, but a detection limit of the central image is obtained at 3$\sigma$ detection level which is 43.8 $\mu$Jy. We performed central image modelling by selecting 29 galaxies sample as the comparison lensing galaxy of B2319+051 which fits the flux ratio and separation of the two arcsecond-scale images of B2319+051, in two cases with and without a central black hole. Our modelling analysis suggests that we cannot attribute the lack of a detection of the central image to the presence of a black hole in the lensing galaxies, the distribution of mass in the inner part of the lensing galaxy is likely the reason for the non-detection. We also use the central image detection limit to constrain the range of the core radius which should be less than 6.3 mas, corresponding to 158 parsecs. More two-image systems need to be observed to statistically constrain the inner mass distribution of massive elliptical lensing galaxies.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Neal Jackson (Supervisor) & Rene Breton (Supervisor)