The nature of massive black hole binary candidates - II. Spectral energy distribution atlas

Recoiling supermassive black holes (SMBHs) are considered one plausible physical mechanism to explain high velocity shifts between narrow and broad emission lines sometimes observed in quasar spectra. If the sphere of influence of the recoiling SMBH is such that only the accretion disc is bound, the dusty torus would be left behind, hence the SED should then present distinctive features (i.e. a mid-infrared deficit). Here, we present results from fitting the spectral energy distributions (SEDs) of 32 type-1 AGN with high velocity shifts between broad and narrow lines. The aim is to find peculiar properties in the multiwavelength SEDs of such objects by comparing their physical parameters (torus and disc luminosity, intrinsic reddening, and size of the 12 μm emitter) with those estimated from a control sample of ~1000 typical quasars selected from the Sloan Digital Sky Survey in the same redshift range. We find that all sources, with the possible exception of J1154+0134, analysed here present a significant amount of 12 μm emission. This is in contrast with a scenario of an SMBH displaced from the centre of the galaxy, as expected for an undergoing recoil event.