Direct measurement of lensing amplification in Abell S1063 using a strongly lensed high redshift HII Galaxy

TL;DR

This study directly measures the gravitational lensing amplification of a high-redshift star-forming galaxy using the L-sigma relation, confirming model predictions and demonstrating a new method for lensing quantification.

Contribution

It introduces a novel approach to measure lensing amplification through the L-sigma relation in lensed high-redshift HII galaxies, providing an independent verification of lensing models.

Findings

Measured lensing amplification of ID11 as 23 ± 11.

Results support the validity of the L-sigma relation for high-z low luminosity objects.

Findings are consistent with lensing model estimates within errors.

Abstract

ID11 is an actively star forming extremely compact galaxy and Ly alpha emitter at z=3.117 that is gravitationally magnified by a factor of ~17 by the cluster of galaxies Hubble Frontier Fields AS1063. Its observed properties resemble those of low luminosity HII galaxies or Giant HII regions like 30-Doradus in the LMC. Using the tight correlation correlation between the Balmer-line luminosities and the width of the emission lines (typically L(Hbeta)-sigma(Hbeta)) valid for HII galaxies and Giant HII regions to estimate its total luminosity, we are able to measure the lensing amplification of ID11. We obtain an amplification of 23 +- 11 similar within errors to the value of ~17 estimated or predicted by the best lensing models of the massive cluster Abell S1063. We also compiled from the literature luminosities and velocity dispersions for a set of lensed compact starforming regions. There is more scatter in the L-sigma correlation for these lensed systems but on the whole the results tend to support the lensing models estimates of the magnification. Our result indicates that the amplification can be independently measured using the L-sigma relation in lensed Giant HII regions or HII galaxies. It also supports the suggestion, even if lensing model dependent, that the L-sigma relation is valid for low luminosity high-z objects. Ad-hoc observations of lensed starforming systems are required to accurately determine the lensing amplification.