SIMBAD references

We report the detection of differential gas column densities in three gravitational lenses, MG 0414+0534, HE 1104-1805, and PKS 1830-211. Combined with the previous differential column density and extinction measurements in B1600+434 and Q2237+0305, we probe the dust-to-gas ratio of a small sample of cosmologically distant normal galaxies. We obtain an average dust-to-gas ratio of E(B-V)/N_H=(1.4±0.5)x10^–22 mag.cm²/atoms, with an estimated intrinsic dispersion in the ratio of ≃40%. This average dust-to-gas ratio is consistent with the average Galactic value of 1.7x10^–22 mag.cm²/atoms, and the estimated intrinsic dispersion is also consistent with the 30% observed in the Galaxy.