The host galaxies of luminous type 2 AGNs at z ∼ 0.3-0.4

We study the morphological and structural properties of the host galaxies associated with 57 optically selected luminous type 2 active galactic nuclei (AGNs) at z similar to 0.3-0.4: 16 high-luminosity Seyfert 2 [HLSy2, 8.0 <= log(L-[O III]/L-circle dot) < 8.3] and 41 obscured [QSO2, log(L-[O III]/L-circle dot) >= 8.3] quasars. With this work, the total number of QSO2s at z < 1 with parametrized galaxies increases from similar to 35 to 76. Our analysis is based on Hubble Space Telescope WFPC2 and ACS images that we fit with GALFIT. HLSy2s and QSO2s show a wide diversity of galaxy hosts. The main difference lies in the higher incidence of highly disturbed systems among QSO2s. This is consistent with a scenario in which galaxy interactions are the dominant mechanism triggering nuclear activity at the highest AGN power. There is a strong dependence of galaxy properties with AGN power (assuming L-[O III] is an adequate proxy). The relative contribution of the spheroidal component to the total galaxy light (B/T) increases with L-[O III]. While systems dominated by the spheroidal component spread across the total range of L-[O III], most disc-dominated galaxies concentrate at log(L-[O III]/L-circle dot) < 8.6. This is expected if more powerful AGNs are powered by more massive black holes which are hosted by more massive bulges or spheroids. The average galaxy sizes (< r(e)>) are 5.0 +/- 1.5 kpc for HLSy2s and 3.9 +/- 0.6 kpc for HLSy2s and QSO2s, respectively. These are significantly smaller than those found for QSO1s and narrow-line radio galaxies at similar z. We put the results of our work in the context of related studies of AGNs with quasar-like luminosities.