The intrinsic distribution of Lyman-<i>α</i> halos

The emission and escape of Lyman- α photons from star-forming galaxies is determined through complex interactions between the emitted photons and a galaxy’s interstellar and circumgalactic gas. This causes Lyman- α emitters (LAEs) to commonly appear not as point sources but in spatially extended halos with complex spectral profiles. We developed a 3D spatial-spectral model of Lyman- α halos (LAHs) to replicate LAH observations in integral field spectroscopic studies, such as those made with VLT/MUSE. The profile of this model is a function of six key halo properties: the halo- and compact-source exponential scale lengths ( r sH and r sC ), the halo flux fraction ( f H ), the compact component ellipticity ( q ), the spectral line width ( σ ), and the spectral line skewness parameter ( γ ). Placing a series of model LAHs into datacubes that reflect observing conditions in the MUSE UDF-Mosaic survey, we tested their detection recoverability and determine that σ , r sH , and f H are expected to have the most significant effect on the detectability of the overall LAH at a given central wavelength and intrinsic line luminosity. We developed a general selection function model that spans a grid of these halo parameters. Using it with a sample of 145 LAHs with measured halo properties observed in the UDF-Mosaic survey, we derived completeness-corrected, intrinsic distributions of the values of σ , r sH , and f H for 3 &lt; z &lt; 5 LAHs. We present the best-fit functional forms of the distributions as well as a σ distribution corrected for instrumental line-spread function broadening, and thereby show the physical line-spread distribution of the intrinsic population. Finally, we discuss possible implications for these distributions for the nature of Ly α emission through the circumgalactic medium, finding that observations may undercount LAHs with extended halo scale lengths compared to the intrinsic population.