that with a metallicity threshold in LGRB production (of between $\frac{1}{3}$ to $\frac{1}{2}$ solar) the typical galaxy mass distribution would then reproduce that of the LGRB host galaxy population (i.e. primarily a reduction in the high-mass end of the distribution).

In a similar analysis, [@Perley_shoals_masses] used Spitzer rest-frame near-IR (NIR) luminosity observations to calculate masses for 82 LGRB host galaxies from the Swift GRB Host Galaxy Legacy Survey (SHOALS) and also use the distribution of these masses to estimate a metallicity threshold. However [@Perley_shoals_masses] estimates the metallicity threshold to be much higher at “approximately the solar value." They also find that dust-obscured LGRBs dominate the massive host population while little dust is seen in low-mass hosts and that host metallicity has little impact on LGRB production at z $>$ 1.5 while preventing most LGRB events at lower redshifts.

Here (in [first@refmzd,@]{}) we will fully exploit the new larger emission-line metallicity LGRB host galaxy sample of [@xshooter_survey] (in concert with the @stats_paper sample) to examine how the LGRB metallicity distribution changes with redshift. First however (in [first@refzd,@]{}) we will analyze and address the redshift biases of the different LGRB populations as this is necessary to validate our samples. Also (in [first@refemzd,@]{}), 