Diffuse Lyα haloes around galaxies at z = 2.2–6.6: implications for galaxy formation and cosmic reionization

摘要: We present diffuse Lyman-alpha halos (LAHs) identified in the composite Subaru narrowband images of 100-3600 emitters (LAEs) at z=2.2, 3.1, 3.7, 5.7, and 6.6. First, we carefully examine potential artifacts mimicking LAHs that include a large-scale point-spread function (PSF) made by instrumental atmospheric effects. Based on our critical test with non-LAE samples whose narrowband-magnitude source-size distributions are same as LAE samples, confirm no can produce extended feature similar to LAHs. After this test, measure scale lengths exponential profile for estimated from z=2.2-6.6 L(Lyman-alpha) > 2 x 10^42 erg s^-1. obtain ~ 5-10 kpc z=2.2-5.7, find evolution redshift range beyond measurement uncertainties. Combining result previously-known UV-continuum size evolution, infer ratio LAH sizes is nearly constant z=2.2-5.7. The length z=6.6 larger than just error bar, which hint would increase z=5.7 If confirmed future large surveys significant improvements statistical systematical errors, change z 6 be signature increasing fraction neutral hydrogen scattering photons, due cosmic reionization.