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(Abridged) Since its launch in October 2002, the INTEGRAL satellite hasrevolutionized our knowledge of the hard X-ray sky thanks to its unprecedentedimaging capabilities and source detection positional accuracy above 20 keV.Nevertheless, many of the newly-detected sources in the INTEGRAL sky surveysare of unknown nature. The combined use of available information at longerwavelengths (mainly soft X-rays and radio) and of optical spectroscopy on theputative counterparts of these new hard X-ray objects allows us to pinpointtheir exact nature. Continuing our long-standing program that has been runningsince 2004, and using 6 different telescopes of various sizes, we report theclassification through optical spectroscopy of 22 more unidentified or poorlystudied high-energy sources detected with the IBIS instrument onboard INTEGRAL.We found that 16 of them are active galactic nuclei (AGNs), while the remaining6 objects are within our Galaxy. Among the identified extragalactic sources, 14are Type 1 AGNs; of these, 6 lie at redshift larger than 0.5 and one has z =3.12, which makes it the second farthest object detected in the INTEGRALsurveys up to now. The remaining AGNs are of type 2, and one of them is a pairof interacting Seyfert 2 galaxies. The Galactic objects are identified as twocataclysmic variables, one high-mass X-ray binary, one symbiotic binary and twochromospherically active stars. We thus still find that AGNs are the mostabundant population among hard X-ray objects identified through opticalspectroscopy. Moreover, we note that the higher sensitivity of the more recentINTEGRAL surveys is now enabling the detection of high-redshift AGNs, thusallowing the exploration of the most distant hard X-ray emitting sources andpossibly of the most extreme blazars.

Unveiling the nature of INTEGRAL objects through optical spectroscopy. IX. 22 more identifications, and a glance into the far hard X-ray Universe