Observations of Lensed Relativistic Jets as a Tool of Constraining Lens Galaxy Parameters

TL;DR

This paper explores how observations of lensed relativistic jets can help constrain the parameters of lens galaxies and measure the Hubble constant, emphasizing the importance of jet image angles and small-scale observations.

Contribution

It introduces the jet image position angle as a new parameter to better constrain lens models and discusses the potential of very long baseline interferometry for detailed measurements.

Findings

Jet image position angle helps distinguish between lens models.

Models with at least 40° difference in jet angles are observationally distinguishable.

Observations over several months can measure superluminal velocities of jet knots.

Abstract

The possibility of using lensed relativistic jets on very small angular scales to construct proper models of spiral lens galaxies and to independently determine the Hubble constant is considered. The system B0218+357 is used as an example to illustrate that there exists a great choice of model parameters adequately reproducing its observed large-scale properties but leading to a significant spread in the Hubble constant. The jet image position angle is suggested as an additional parameter that allows the range of models under consideration to be limited. It is shown that the models for which the jet image position angles differ by at least $40^o$ can be distinguished between themselves during observations on very small angular scales. The possibility of observing the geometric properties of lensed relativistic jets and measuring the superluminal velocities of knot images on time scales of several months with very long baseline space interferometers is discussed.