The effect of environment on the structure of disc galaxies

Abstract

We study the influence of environment on the structure of disc galaxies, using \texttt{IMFIT} to measure the g- and r-band structural parameters of the surface-brightness profiles for $\sim$700 low-redshift (z$<$0.063) cluster and field disc galaxies with intermediate stellar mass (0.8 $\times$ 10$^{10}$ $M_{\odot}$ $<$ $M_{\star}$ $<$ 4 $\times$ 10$^{10}$ $M_{\odot}$) from the Sloan Digital Sky Survey, DR7. Based on this measurement, we assign each galaxy to a surface-brightness profile type (Type I $\equiv$ single-exponential, Type II $\equiv$ truncated, Type III $\equiv$ anti-truncated). In addition, we measure (g-r) restframe colour for disc regions separated by the break radius. Cluster disc galaxies (at the same stellar mass) have redder (g-r) colour by $\sim$0.2 mag than field galaxies. This reddening is slightly more pronounced outside the break radius. Cluster disc galaxies also show larger global S\'ersic-indices and are more compact than field discs, both by $\sim$15\%. This change is connected to a flattening of the (outer) surface-brightness profile of Type I and - more significantly - of Type III galaxies by $\sim$8\% and $\sim$16\%, respectively, in the cluster environment compared to the field. We find fractions of Type I, II and III of (6$\pm$2)\%, (66$\pm$4)\% and (29$\pm$4)\% in the field and (15$_{-4}^{+7}$)\%, (56$\pm$7)\% and (29$\pm$7)\% in the cluster environment, respectively. We suggest that the larger abundance of Type I galaxies in clusters (matched by a corresponding decrease in the Type II fraction) could be the signature of a transition between Type II and Type I galaxies produced/enhanced by environment-driven mechanisms.