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We present new high-precision measurements of the opacity of theintergalactic and circumgalactic medium (IGM, CGM) at <z>=2.4. Using Voigtprofile fits to the full Lyman alpha and Lyman beta forests in 15high-resolution high-S/N spectra of hyperluminous QSOs, we make the firststatistically robust measurement of the frequency of absorbers with HI columndensities 14 < log(NHI) < 17.2. We also present the first measurements of thefrequency distribution of HI absorbers in the volume surrounding high-zgalaxies (the CGM, 300 pkpc), finding that the incidence of absorbers in theCGM is much higher than in the IGM. In agreement with Rudie et al. (2012), wefind that there are fractionally more high-NHI absorbers than low-NHI absorbersin the CGM compared to the IGM, leading to a shallower power law fit to the CGMfrequency distribution. We use these new measurements to calculate the totalopacity of the IGM and CGM to hydrogen-ionizing photons, finding significantlyhigher opacity than most previous studies, especially from absorbers withlog(NHI) < 17.2. Reproducing the opacity measured in our data as well as theincidence of absorbers with log(NHI) > 17.2 requires a broken power lawparameterization of the frequency distribution with a break near log(NHI) ~ 15.We compute new estimates of the mean free path (mfp) to hydrogen-ionizingphotons at z=2.4, finding mfp = 147 +- 15 Mpc when considering only IGMopacity. If instead, we consider photons emanating from a high-z star-forminggalaxy and account for the local excess opacity due to the surrounding CGM ofthe galaxy itself, the mean free path is reduced to mfp = 121 +- 15 Mpc. Thesemfp measurements are smaller than recent estimates and should inform futurestudies of the metagalactic UV background and of ionizing sources at z~2-3.

The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift =2.4