On The Reddening in X-ray Absorbed Seyfert 1 Galaxies

Abstract

There are several Seyfert galaxies for which there is a discrepancy between the small column of neutral hydrogen deduced from X-ray observations and the much greater column derived from the reddening of the optical/UV emission lines and continuum. The standard paradigm has the dust within the highly ionized gas which produces O~VII and O~VIII absorption edges (i.e., a ``dusty warm absorber''). We present an alternative model in which the dust exists in a component of gas in which hydrogen has been stripped, but which is at too low an ionization state to possess significant columns of O~VII and O~VIII (i.e, a ``lukewarm absorber''). The lukewarm absorber is at sufficient radial distance to encompass much of the narrow emission-line region, and thus accounts for the narrow-line reddening, unlike the dusty warm absorber. We test the model by using a combination of photoionization models and absorption edge fits to analyze the combined ROSAT/ASCA dataset for the Seyfert 1.5 galaxy, NGC 3227. We show that the data are well fit by a combination of the lukewarm absorber and a more highly ionized component similar to that suggested in earlier studies. We predict that the lukewarm absorber will produce strong UV absorption lines of N V, C IV, Si IV and Mg II. Finally, these results illustrate that singly ionized helium is an important, and often overlooked, source of opacity in the soft X-ray band (100 - 500 eV).

17 pages, Latex, includes 1 figure (encapsulated postscript), one additional table in Latex (landscape format), to appear in the Astrophysical Journal

References in corpus (5)

• Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from the Hubble Space Telescope
• STIS Longslit Spectroscopy of the Narrow-Line Region of NGC 4151. II. Physical Conditions along Position Angle 221 Degress
• Intrinsic Absorption Lines in the Seyfert 1 Galaxy NGC 5548: UV Echelle Spectra from the Space Telescope Imaging Spectrograph
• STIS Longslit Spectroscopy Of The Narrow Line Region Of NGC 4151. I. Kinematics and Emission Line Ratios
• The X-ray Spectral Variability of the Seyfert Galaxy NGC 3227

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• Absorption and Reddening in the Seyfert Galaxy NGC 3227
• An absorption origin for the soft excess in Seyfert 1 AGN
• Reddening, Emission-Line, and Intrinsic Absorption Properties in the Narrow-Line Seyfert 1 Galaxy Akn 564
• Variable UV Absorption in the Seyfert 1.5 Galaxy NGC 3516: The Case for Associated UV and X-ray Absorption
• A Comprehensive X-ray Spectral Analysis of the Seyfert 1.5 NGC 3227
• Ultraviolet and optical properties of Narrow-Line Seyfert 1 galaxies
• Radiation Pressure Confinement -- III. The origin of the broad ionization distribution in AGN outflows
• On the Nature of Intrinsic Absorption in Reddened Seyfert 1 Galaxies
• A rapid occultation event in NGC 3227
• Multi-wavelength Probes of Obscuration Towards the Narrow Line Region in Seyfert Galaxies
• A Variable-Density Absorption Event in NGC 3227 mapped with Suzaku and Swift
• On the Location and Composition of the Dust in the MCG-6-30-15 Warm Absorber
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• Far Ultraviolet Spectroscopic Explorer Spectroscopy of Absorption and Emission Lines from the Narrow-Line Seyfert 1 Galaxy NGC 4051
• Combined Analysis of X-Ray Spectra of NGC 3227