The sizes of disc galaxies in intermediate-redshift clusters

We examine how the location of star formation within disc galaxies depends on environment at intermediate redshift. This is achieved by comparing emission-line (rem) and rest-frame B-band (rB) scalelengths for matched samples of 50 field and 19 cluster, star-forming, disc galaxies, with 0.25 ≤z≤ 1.0 and MB≤−19.5 mag. We find that at a given rB the majority of our cluster galaxies have rem smaller than those in the field, by 25 per cent on average. These results are compared with studies of local galaxies, which find a very similar behaviour. From the relations of rem and rB versus B-band absolute magnitude (MB) we infer that the difference between the intermediate-z cluster and field samples is mostly attributable to variation in rem at a given MB, while the rB versus MB relation is similar for the two samples.