Association of optical, ultraviolet, and soft X-ray excess emissions in AGNs

Soft X-ray emission (0.5-2.0 keV) plays a pivotal role in regulating the optical and ultraviolet (UV) emission in the active galactic nuclei (AGNs). We collected a sample of 1811 AGNs from the SDSS database and obtained various parameters of Balmer lines, optical continuum, Mg II line & UV continuum and studied their dependencies on soft X-ray luminosity. Based on the linear regression analysis, we found that FWHMMg II proportional to FWHMH beta 0 . 554 suggesting that UV emission is arising from a region relatively outside the broad-line region (BLR) associated to the H beta emission and found a strong correlation between optical and UV luminosities (L-Mg II proportional to L (0 . 822)(H beta)). It was noticed that the dependency of optical continuum luminosities on soft excess changes with the redshift (L-X proportional to L (0 . 596)(5100 angstrom) for z < 0.5 and L-X proportional to L 0 . 429 5100 angstrom for z > 0.5). The full width at half-maximum components of H SB and Mg II core components were found to be virialized and is not affected by the soft excess emission whereas the wings of Mg II display a dependency. We estimated a relation viz. L-X proportional to L0(3000 angstrom)(0.520) FWHMMg II0 . 525 and found to be well in agreement with a proposed physical scenario. All the derived relations were used to understand the intermodulating association of the BLR and disc in the AGNs.

Automated summary

Soft X-ray emission is crucial in regulating the optical and UV emission in AGNs. A study of 1811 AGNs showed dependencies between various parameters and soft X-ray luminosity. The analysis found a correlation between FWHMMg II and FWHMH beta 0.554, suggesting the UV emission comes from a region outside the BLR associated with H beta emission. Strong correlations were also found between optical and UV luminosities. The dependencies of optical continuum luminosities on soft excess changed with redshift.