The location of the dust causing internal reddening of active galactic nuclei

Abstract

We use the Balmer decrements of the broad-line regions (BLRs) and narrow-line regions (NLRs) of active galactic nuclei (AGNs) as reddening indicators to investigate the location of the dust for four samples of AGNs with reliable estimates of the NLR contribution to the Balmer lines. Intercomparison of the NLR and BLR Balmer decrements indicates that the reddening of the NLR sets a lower limit to the reddening of the BLR. Almost no objects have high NLR reddening but low BLR reddening. The reddening of the BLR is often substantially greater than the reddening of the NLR. The BLR reddening is correlated with the equivalent widths of [O III] lines and the intensity of the [O III] lines relative to broad Hβ. We find these relationships to be consistent with the predictions of a simple model where the additional dust reddening the BLR is interior to the NLR. We thus conclude that the dust causing the additional reddening of the accretion disc and BLR is mostly located at a smaller radius than the NLR.

arXiv commentMonthly Notices of the Royal Astronomical Society in press. 6 pages. 6 figures

References in corpus (9)

• The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• What broad emission lines tell us about how active galactic nuclei work
• A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Results
• The FIRST-2MASS Red Quasar Survey
• Spectral Decomposition of Broad-Line AGNs and Host Galaxies
• The Size of the Narrow-Line Emitting Region in the Seyfert 1 Galaxy NGC 5548 from Emission-Line Variability
• Partially obscured quasars in the Sloan Digital Sky Survey Early Data Release
• Radio and optical orientations of galaxies

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