Diffuse Lyα haloes around Lyα emitters at z=3: do dark matter distributions determine the Lyα spatial extents?

Abstract

Using stacks of Ly-a images of 2128 Ly-a emitters (LAEs) and 24 protocluster\nUV-selected galaxies (LBGs) at z=3.1, we examine the surface brightness\nprofiles of Ly-a haloes around high-z galaxies as a function of environment and\nUV luminosity. We find that the slopes of the Ly-a radial profiles become\nflatter as the Mpc-scale LAE surface densities increase, but they are almost\nindependent of the central UV luminosities. The characteristic exponential\nscale lengths of the Ly-a haloes appear to be proportional to the square of the\nLAE surface densities (r(Lya) \\propto Sigma(LAE)^2). Including the diffuse,\nextended Ly-a haloes, the rest-frame Ly-a equivalent width of the LAEs in the\ndensest regions approaches EW_0(Lya) ~ 200 A, the maximum value expected for\nyoung (< 10^7 yr) galaxies. This suggests that Ly-a photons formed via shock\ncompression by gas outflows or cooling radiation by gravitational gas inflows\nmay partly contribute to illuminate the Ly-a haloes; however, most of their\nLy-a luminosity can be explained by photo-ionisation by ionising photons or\nscattering of Ly-a photons produced in HII regions in and around the central\ngalaxies. Regardless of the source of Ly-a photons, if the Ly-a haloes trace\nthe overall gaseous structure following the dark matter distributions, it is\nnot surprising that the Ly-a spatial extents depend more strongly on the\nsurrounding Mpc-scale environment than on the activities of the central\ngalaxies.\n