G22A001

A magnified view of an ionised scattering medium in a z= 1.145 late- type galaxy

Abstract

The properties of ionised mediums within galaxies are important for studying star formation
and galaxy formation, but measuring the electron density of ionised mediums in high-redshift
galaxies is very challenging. A multiple-image strong lensing system offers a unique view into
the ionised medium in the lensing galaxy. Lensed images show different views of the same
source affected by scatter broadening and free-free absorption. The quadruple lens system
B0128+437 is affected by both scattering and free-free absorption. We request high-
sensitivity multi-frequency global VLBI observations to image the scatter-broadened lensed
image in B0128+437, and resolve the core-jet structure represented by the three
subcomponents in each lensed image. Taking advantage of scattering size scaled by the
lensing magnification, the inhomogeneous ionised scattering medium can be resolved down
to sub-parsec physical scales at redshift 1.145. The constraints from the image
subcomponents will tightly constrain the lens model. Additionally, these data will quantify the
flux ratio anomaly caused by free-free absorption. Modelling such propogation effects in this
lens system will reduce the systematics for the constraints on the nature of dark matter given
by this system.

Investigators

Name	Institution
Di Wen *	Kapteyn Astronomical Institute
John McKean	Netherlands Institute for Radio Astronomy; Kapteyn Astronomical Institute
Simon Ndiritu	Max-Planck-Institut für Astrophysik
Devon Powell	Stanford University
Simona Vegetti	Massachusetts Institute of Technology
GBT Operator	Green Bank Observatory

* indicates the PI