MULTI-WAVELENGTH PROBES OF OBSCURATION TOWARD THE NARROW-LINE REGION IN SEYFERT GALAXIES
- Department of Physics, Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, DC 20064 (United States)
- Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375 (United States)
- Department of Physics and Astronomy, Georgia State University, Astronomy Offices, Atlanta, GA 30303 (United States)
- Henry A. Rowland Department of Physics and Astronomy, Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States)
- Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250 (United States)
- European Space Astronomy Centre of the European Space Agency, P.O. Box 78, Villanueva de la Canada, e-28691 Madrid (Spain)
- Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
We present a study of reddening and absorption toward the narrow line regions (NLRs) in active galactic nuclei (AGNs) selected from the Revised Shapley-Ames, 12 {mu}m, and Swift/Burst Alert Telescope samples. For the sources in host galaxies with inclinations of b/a > 0.5, we find that the mean ratio of [O III] {lambda}5007, from ground-based observations, and [O IV] 28.59 {mu}m, from Spitzer/Infrared Spectrograph observations, is a factor of two lower in Seyfert 2s than Seyfert 1s. The combination of low [O III]/[O IV] and [O III] {lambda}4363/{lambda}5007 ratios in Seyfert 2s suggests more extinction of emission from the NLR than in Seyfert 1s. Similar column densities of dusty gas, N{sub H}{approx} several x 10{sup 21} cm{sup -2}, can account for the suppression of both [O III] {lambda}5007 and [O III] {lambda}4363, as compared to those observed in Seyfert 1s. Also, we find that the X-ray line O VII {lambda}22.1 A is weaker in Seyfert 2s, consistent with absorption by the same gas that reddens the optical emission. Using a Hubble Space Telescope/Space Telescope Imaging Spectrograph slitless spectrum of the Seyfert 1 galaxy NGC 4151, we estimate that only {approx}30% of the [O III] {lambda}5007 comes from within 30 pc of the central source, which is insufficient to account for the low [O III]/[O IV] ratios in Seyfert 2s. If Seyfert 2 galaxies have similar intrinsic [O III] spatial profiles, the external dusty gas must extend further out along the NLR, perhaps in the form of nuclear dust spirals that have been associated with fueling flows toward the AGN.
- OSTI ID:
- 21567524
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 727; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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