Low and high surface brightness galaxies at void walls

We study the relative fraction of low and high surface brightness galaxies (LSBGs and HSBGs) at void walls in the Sloan Digital Sky Survey (SDSS) Data Release 7. We focus on galaxies in equal local density environments. We assume that the host dark matter halo mass (for which we use SDSS group masses) is a good indicator of local density. This analysis allows us to examine the behaviour of the abundance of LSBGs and HSBGs at a fixed local density and distinguish the large-scale environment defined by the void geometry. We compare galaxies in the field and in the void walls; the latter are defined as the volume of void shells of radius equal to that of the void. We find a significant decrement, a factor of similar to 4, of the relative fraction of blue, active star-forming LSBGs in equal-mass groups at the void walls and the field. This decrement is consistent with an increase of the fraction of blue, active star-forming HSBGs. In contrast, red LSBGs and HSBGs show negligible changes. We argue that these results are consistent with a scenario where LSBGs with blue colours and strong star formation activity at the void walls are fuelled by gas from the expanding void regions. This process could lead to LSBG to HSBG transformations.