The case against large intensity fluctuations in the z ∼ 2.5 He ii Lyα forest

摘要: Previous studies of the 2.2 < z< 2.7 HeII Lyman-alpha forest measured much larger ionizing background fluctuations than are anticipated theoretically. We re-analyze recent Hubble Space Telescope data from two sightlines that have been used to make these measurements, HE2347-4342 and HS1700+6416, find vast majority absorption is actually consistent with a single photoionization rate. show constrains RMS fractional fluctuation level smoothed at 1 Mpc be 2 discuss why other had found fluctuations. Our measurement models in which quasars dominate z=2.5 metagalactic HeII-ionizing (but it can accommodate less compelling models), suggests (rather stars) dominant contributor HI-ionizing background. detect transverse proximity effect slightly offset redshift known quasar. Its profile may indicate quasar turned on 10 Myr ago.