BAT AGN Spectroscopic Survey – XIII. The nature of the most luminous obscured AGN in the low-redshift universe

We present a multi wavelength analysis of the 28 most luminous low-redshift narrow-line,ultra-hard X-ray selected active galactic nuclei (AGN) within the 70 month Swift/BAT all-skysurvey, with bolometric luminosities of log¹Lbolerg s􀀀1º > 45:25. The broad goal of our studyis to determine whether these objects have any common characteristics, potentially settingthem aside from lower-luminosity obscured AGN in the local Universe. Our analysis relies onthe first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicatedobservations with the VLT, Palomar, and Keck observatories.We find that the vast majority ofour sources agree with commonly used AGN selection criteria which are based on emissionline ratios and on mid-infrared colours, and furthermore that our AGN are predominantlyhosted in massive, elliptical galaxies (9:8 < log¹MMº < 11:7). Otherwise, they do nothave common characteristics. Their radio luminosities, determined from publicly availablesurvey data, show a large spread of almost 4 orders of magnitude in - much broader than whatis found for lower X-ray luminosity, obscured AGN in BASS. Moreover, our sample showsno preferred combination of black hole masses (MBH) and/or Eddington ratio (Edd), covering7:5 < log¹MBHMº < 10:3 and 0:01 . Edd . 1. Based on the distribution of our sourcesin the Edd 􀀀 NH plane, we conclude that our sample is consistent with a scenario wherethe amount of obscuring material along the line of sight is determined by radiation pressureexerted by the AGN on the dusty circumnuclear gas.