Radio Observations of Strong Gravitational Lenses

Abstract

Strong gravitational lensing can magnify the background source, allowing us to study distant and faint objects. Observations with radio interferometry offer an incredible resolution to resolve the lenses. Here, we focused on lensed radio-quiet quasars (RQQs) and high-redshift submm bright galaxies (SMGs). The radio emission mechanism of RQQs has been in debate, mostly between star formation of their host galaxies or AGN activities. We present the mas-resolution e-MERLIN C-band and EVN L-band observations of the 2-image lens SDSS J1128+2402. We detected the source at > 5σ in both bands. The northeast component in the e-MERLIN map falls below 3σ, giving a larger flux ratio than EVN and other studies (~2). A high brightness temperature TB ≥ 5.3e5 K and a steep spectrum at 6 GHz indicate that the AGN jet or corona produces the radio emission of J1128+2402. The visibility-plane fitting yields marginal evidence that the southwest component is extended by ~10 mas. The southwest component has a flat 1.6 − 5 GHz spectrum. Source variability is suggested by the difference in the spectral index of the 2 components. The SMGs are galaxies with very high rates of star formation. We studied 4 H-ATLAS lensed galaxies in the L-band with e-MERLIN and detected J1324+2844 and J1344+3030 at > 5σ, and J1335+3004 at > 4σ. Their radio emission is generally aligned with the SMGs. The radio sizes of J1324+2844 and J1344+3030 are comparable with their submm counterparts. We present the visibility-plane lens modeling of J1344+3030. We also detected a radio galaxy at > 5σ near the Herschel positions of J1339+3408 that can be its radio counterpart given the astrometric errors of Herschel. The Far-infrared (FIR)-radio indexes of our SMGs are around the FIR-radio correlation for star-forming galaxies. In addition, we tried detecting the central "odd" image in several radio-loud lenses. This heavily demagnified image can be used to probe the central stellar density and supermassive black hole mass. We obtained a deep e-MERLIN measurement of CLASS B2319+051 in the C-band. The result is a non-detection with a 99% limit Fc < 35.7 μJy. We constrained the lens galaxy's central mass slope and break radius of the Nuker's profile for different SMBH masses. The e-MERLIN data of PKS 1830-211 and CLASS B0739+366 are too bad to obtain useful constraints on the central image.

Date of Award	21 Jan 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Christopher Conselice (Co Supervisor) & Neal Jackson (Main Supervisor)