Diffuse Ly\ensuremathα haloes around Ly\ensuremathα emitters at z=3: do dark matter distributions determine the Ly\ensuremathα spatial extents?
Matsuda, Y., Yamada, T., Hayashino, T., Yamauchi, R., Nakamura, Y., Morimoto, N., Ouchi, M., Ono, Y., Umemura, M., & Mori, M.
Using stacks of Ly\ensuremathα images of 2128 Ly\ensuremathα emitters (LAEs) and 24 proto-cluster UV- selected galaxies (LBGs) at z = 3.1, we examine the surface brightness profiles of Ly\ensuremathα haloes around high-z galaxies as a function of environment and UV luminosity. We find that the slopes of the Ly\ensuremathα radial profiles become flatter as the Mpc-scale LAE surface density increases, but that they are almost independent of the central UV luminosity. The characteristic exponential scalelength of the Ly\ensuremathα haloes appears to be proportional to the square of the LAE surface density (r Ly \ensuremathα\ensuremath∝\ensuremathΣ LAE 2). Including the diffuse, extended Ly\ensuremathα haloes, the rest-frame Ly\ensuremathα equivalent width of the LAEs in the densest regions approaches EW$_0$ ̃ 200 ̊A, the maximum value expected for young (<10$^7$ yr) galaxies. This suggests that Ly\ensuremathα photons formed via shock compression by gas outflows or cooling radiation by gravitational gas inflows may partly contribute to the illumination of Ly\ensuremathα haloes; however, most of their Ly\ensuremathα luminosity can be explained by photoionization by or by scattering of Ly\ensuremathα photons produced from H II regions in and around the central galaxies. Regardless of the source of Ly\ensuremathα photons, if the Ly\ensuremathα haloes trace the overall gaseous structure, following the dark matter distribution, it is not surprising that the Ly\ensuremathα spatial extent depends more strongly on the surrounding Mpc-scale environment than on the activity of the central galaxies.