Chandra observations of a complete , flux-limited sample of 38 high-redshift ( 1 < z < 2 ) , low-frequency selected ( and so unbiased in orientation ) 3CRR radio sources are reported .
The sample includes 21 quasars ( = broad line radio galaxies ) and 17 narrow line radio galaxies ( NLRGs ) with matched 178 MHz radio luminosity ( log L _ { R } ( 5 ~ { } GHz ) \sim 44 - 45 ) .
The quasars have high radio core-fraction , high X-ray luminosities ( log L _ { X } \sim 45 - 46 ) and soft X-ray hardness ratios ( HR \sim - 0.5 ) indicating low obscuration .
The NLRGs have lower core-fraction , lower apparent X-ray luminosities ( log L _ { X } \sim 43 - 45 ) and mostly hard X-ray hardness ratios ( HR > 0 ) indicating obscuration ( { N _ { H } } \sim 10 ^ { 22 - 24 } cm ^ { -2 } ) .
These properties and the correlation between obscuration and radio core-fraction are consistent with orientation-dependent obscuration as in Unification models .
About half the NLRGs have soft X-ray hardness ratios and/or high [ OIII ] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick ( CT ) material so that scattered nuclear or extended X-ray emission dominates ( as in NGC1068 ) .
The ratios of unobscured to Compton-thin ( 10 ^ { 22 } < { N _ { H } } ( int ) < 1.5 \times 10 ^ { 24 } cm ^ { -2 } ) to CT ( { N _ { H } } ( int ) > 1.5 \times 10 ^ { 24 } cm ^ { -2 } ) is 2.5:1.4:1 in this high luminosity , radio-selected sample .
The obscured fraction is 0.5 , higher than is typically reported for AGN at comparable luminosities from multi-wavelength surveys ( 0.1 - 0.3 ) .
Assuming random nuclear orientation , the unobscured half-opening angle of the disk/wind/torus structure is \sim 60 ^ { o } and the obscuring material covers 30 ^ { o } of which \sim 12 ^ { o } is Compton thick .
The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10 - 1000 \times higher than indicated by their X-ray hardness ratios , and their true L _ { X } values are \sim 10–100 \times larger than the hardness-ratio absorption corrections would indicate .