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S.B. Kraemer (CUA), D.M. Crenshaw (GSU), J.R. Gabel (U. of Colorado), I.M. George (UMBC)
We report the results of combined Chandra, HST/STIS, and FUSE observations of the intrinsic absorption in the Seyfert 1 galaxy NGC 4151. Our previous studies revealed an unusually large column (NH = 1021.5 cm-2) of outflowing gas (vr = -490 km/sec) very close to the nucleus (d < 0.03 pc), which responds rapidly to changes in the ionizing continuum due to its high density (nH > 109 cm-3). With the latest observations, we have discovered evidence that the large absorbing column consists of individual high and low ionization components, and that the column density of the latter has decreased due to bulk motion across our line-of-sight. The Chandra spectra have revealed the signature of both very high ionization lines such as H-like and He-like Si, and inner-shell lines from low ionization species which must be associated with the UV absorbers. With the FUSE observations, we have detected lines from P~V, S~III, and S~IV, which have permitted us to better constrain the physical conditions and covering factors of the UV absorbers. These results indicate a complex and heterogeneous absorbing system, the extreme properties of which are likely the result of a relatively large viewing angle with respect to the accretion-disk axis (i.e., near the edge of the ionization bicone).
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.