Relations between optical spectral parameters and the (far-)infrared continuum in Type 1 active galactic nuclei

Abstract

This study combines multi-wavelength continuum data with optical spectral properties for a specific, far-infrared (FIR)-selected sample from AKARI data of Type 1 active galactic nuclei (AGNs). We explore the relation between AGN physics and concomitant star formation processes using empirical correlations of optical and multiwavelength data. We measured several spectral parameters including the full width at half maximums (FWHMs) and velocity shifts of broad and narrow optical emission lines, as well as continuum luminosities in bands ranging from the GALEX FUV to the 160 micron band of AKARI. The data sample contains 88 AGNs observed at both optical and FIR wavelengths. The sample encompasses ∼50% of Seyfert 1s with detection of both broad Hβ and Hα lines; almost all of the remaining objects can be classified as S1.9 objects where only broad Hα is visible. The FWHM of the broad Hβ and Hα lines are anti-correlated with luminosity in most of the bands. Shifts of narrow Hβ, Hα, and O,III 5007 lines and FWHM O,III 5007 are correlated with optical and IR luminosities. The luminosities at 65 and 90 μm are more strongly connected with optical and other spectral properties than the ones at 140 and 160 μm. The trends presented in this paper extend the well-known Eigenvector 1 (EV1) correlations into the MIR and FIR domain. The anti-correlation trend between FWHM of broad lines and NIR and MIR luminosities is probably caused by the inclination of the torus and accretion disc: higher inclinations see less radiation of the AGN. However, the majority of objects fall into Population A along the quasar EV1 main sequence, for which narrower broad Hβ profiles and FIR excess emission are commonly linked to higher Eddington ratios.