2016A&A...596A..20V

Aims. Indirectly resolving the line-emitting gas regions in distant active galactic nuclei (AGN) requires both high-resolution photometry and spectroscopy (i.e. through reverberation mapping). Emission in AGN originates on widely different scales; the broad-line region (BLR) has a typical radius less than a few parsec, the narrow-line region (NLR) extends out to hundreds of parsecs. But emission also appears on large scales from heated nebulae in the host galaxies (tenths of kpc).
Methods. We propose a novel, data-driven method based on correlations between emission-line fluxes to identify which of the emission lines are produced in the same kind of emission-line regions. We tested the method on Seyfert galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) and Galaxy Zoo project.
Results. We demonstrate the usefulness of the method on Seyfert-1s and Seyfert-2 objects, showing similar narrow-line regions (NLRs). Preliminary results from comparing Seyfert-2s in spiral and elliptical galaxy hosts suggest that the presence of particular emission lines in the NLR depends both on host morphology and eventual radio-loudness. Finally, we explore an apparent linear relation between the final correlation coefficient obtained from the method and time lags as measured in reverberation mapping for Zw 229-015.