VLT FORS2 optical imaging and spectroscopy of nine luminous type 2 AGN at 0.3 < z < 0.6 - I. Ionized gas nebulae

We present optical imaging and long slit spectroscopic observations of nine luminous type 2 active galactic nuclei (AGN) within the redshift range 0.3 < z < 0.6 based on Very Large Telescope Focal Reducer and Low Dispersion Spectrograph (VLT FORS2) data. Most objects (6/9) are high luminosity Seyfert 2, and three are type 2 quasars (QSO2), with our sample extending to lower luminosity than previous works. Seven out of nine objects (78 per cent) showmorphological evidence for interactions or mergers in the form of disturbed morphologies and/or peculiar features such as tidal tails, amorphous haloes, or compact emission line knots. The detection rate of morphological evidence for interaction is consistent with those found during previous studies of QSO2 at similar z, suggesting that the merger rate is independent of AGN power at the high end of the AGN luminosity function.We find the emission line flux spatial profiles are often dominated by the often spatially unresolved central source. In addition, all but one of our samples is associated with much fainter, extended line emission. We find these extended emission line structures have a variety of origins and ionization mechanisms: star-forming companions, tidal features, or extended ionized nebulae. AGN related processes dominate the excitation of the nuclear gas. Stellar photoionization sometimes plays a role in extended structures often related to mergers/interactions.We thank the staff at Paranal Observatory for their support during the observations. AH acknowledges Fundaciao para a Ciencia e a Tecnologia (FCT) support through UID/FIS/04434/2013, and through project FCOMP-01-0124-FEDER-029170 (Reference FCT PTDC/FISAST/3214/2012) funded by FCT-MEC (PIDDAC) and FEDER (COMPETE), in addition to FP7 project PIRSES-GA-2013-612701. AH also acknowledges a Marie Curie Fellowship cofunded by the FP7 and the FCT (DFRH/WIIA/57/2011) and FP7/FCT Complementary Support grant SFRH/BI/52155/2013 MVM and SA acknowledge support from the Spanish Ministerio de Economıa y Competitividad through the grants AYA2012-32295 and AYA-2012-39408-C02-01. CRA is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). RGD acknowledges support through the grant AYA2010-15081