Differential X-ray Absorption and Dust-To-Gas Ratios of the Lens Galaxies SBS0909+523, FBQS0951+2635, and B1152+199

TL;DR

This study measures differential X-ray absorption and dust-to-gas ratios in three gravitational lens galaxies, expanding the sample and confirming ratios consistent with the Milky Way, while also observing microlensing and variability.

Contribution

It provides new measurements of dust-to-gas ratios in distant galaxies, increasing the sample size and confirming their similarity to Galactic values.

Findings

Detected differential X-ray absorption in two lens galaxies.

Measured average dust-to-gas ratio consistent with the Milky Way.

Observed X-ray microlensing and variability in the sample.

Abstract

We analyzed Chandra observations of three gravitational lenses, SBS0909+523, FBQS0951+2635, and B1152+199, to measure the differential X-ray absorption and the dust-to-gas ratio of the lens galaxies. We successfully detected the differential X-ray absorption in SBS0909+523 and B1152+199, and failed to detect it in FBQS0951+2635 due to the dramatic drop in its flux from the ROSAT epoch. These measurements significantly increase the sample of dust-to-gas ratio measurements in cosmologically-distant, normal galaxies. Using the larger sample, we obtain an average dust-to-gas ratio of E(B-V)/NH = (1.5\pm0.5)e-22 mag cm^2/atoms with an estimated intrinsic dispersion in the ratio of \simeq 40%. This average dust-to-gas ratio is consistent with our previous measurement, and the average Galactic value of 1.7e-22 mag cm^2/atoms and the estimated intrinsic dispersion is also consistent with the 30% observed in the Galaxy. A larger sample size is still needed to improve the measurements and to begin studying the evolution in the ratio with cosmic time. We also detected X-ray microlensing in SBS0909+523 and significant X-ray variability in FBQS0951+2635.