Fig. 1: Overdensity of Lyman-α emitting galaxies in the circumgalactic environment around the hyper-luminous W0410-0913, at z = 3.631.

a We show a collage of Lyman-α flux maps showing the projected spatial distribution of 24 Lyman-α-emitting companion galaxies revealed by MUSE in the field of W0410-0913. We applied a spatial Gaussian filtering of 1 pixel (0.2″) to the cutouts and we set a lower bound of \({{{{{{{\rm{SB}}}}}}}}=5\times 1{0}^{-18}\,{{{{{{{\rm{erg}}}}}}}}\,{{{{{{{{\rm{s}}}}}}}}}^{-1}\,{{{{{{{{\rm{cm}}}}}}}}}^{-2}\,{{{{{{{{\rm{arcsec}}}}}}}}}^{-2}\) in the color-scale to improve the visualization. The Lyman-α emitters are distributed on scales of about 400 kpc around the W0410-0913 (see the black line, which corresponds to 300 kpc). The size of each cutout varies between 2″ and 4″, and is chosen according to the extensions of the emitting sources. See Table 1 for the definition of IDs and a summary of the measured properties of the Lyman-α emitters. b We color the cutouts shown in panel a according to the offset velocities of the companion galaxies with respect to the systemic redshift of W0410-0913. The redshift of each emitter is traced by the center wavelength obtained through a Gaussian fit of the Lyman-α spectrum. For W0410-0913, at the center, we show the velocity as traced by its Lyman-α, which is blueshifted with respect to the systemic redshift. The offset velocities range between −6.000 km s⁻¹ and 10.000 km s⁻¹. A histogram of their distribution is shown in panel c. Most of the companion galaxies (18 out of 24) show offsets within a smaller velocity range of about [−2.500; +1.500] km s⁻¹. These are more likely subject to the gravitational effect of the central massive object.