RADIAL VELOCITY OFFSETS DUE TO MASS OUTFLOWS AND EXTINCTION IN ACTIVE GALACTIC NUCLEI
- Department of Physics and Astronomy, Georgia State University, Astronomy Offices, One Park Place South SE, Suite 700, Atlanta, GA 30303 (United States)
- Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375 (United States)
- Institute for Astrophysics and Computational Sciences, Department of Physics, The Catholic University of America, Washington, DC 20064 (United States)
- NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
We present a study of the radial velocity offsets between narrow emission lines and host galaxy lines (stellar absorption and H I 21 cm emission) in Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of the Seyferts in the sample show [O III] emission lines with blueshifts with respect to their host galaxies exceeding 50 km s{sup -1}, whereas only 6% show redshifts this large, in qualitative agreement with most previous studies. We also find that a greater percentage of Seyfert 1 galaxies show blueshifts than Seyfert 2 galaxies. Using Hubble Spce Talescope/Space Telescope Imaging Spectrograph spatially resolved spectra of the Seyfert 2 galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models of their narrow-line regions (NLRs) and inner galactic disks, and show how these models can explain the blueshifted [O III] emission lines in collapsed STIS spectra of these two Seyferts. We conclude that the combination of mass outflow of ionized gas in the NLR and extinction by dust in the inner disk (primarily in the form of dust spirals) is primarily responsible for the velocity offsets in Seyfert galaxies. More exotic explanations are not needed. We discuss the implications of this result for the velocity offsets found in higher redshift active galactic nuclei.
- OSTI ID:
- 21392471
- Journal Information:
- Astrophysical Journal, Vol. 708, Issue 1; Other Information: DOI: 10.1088/0004-637X/708/1/419; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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