Parameters for Lyman- forest in Triplet

The quantity we would like to limit is , i.e. the ratio between the transverse comoving distance corresponding to the a small change in the measure wavelength, , of a Ly- absorption to the comoving transvese displacement corresponding to the change in the apparent angular position by and angle . Perhaps a more physical quantity is where &dgr;z gives small change in redshift of the Ly- absorption. The two are related through the relation so where . At the canonical wavelength of 4100Å for the triplet we are at z=2.35 .