1997/06/01 by Joseph C. Shields, Fred Hamann · 36 citations
Physics and Astronomy · #Absorption (acoustics) #Astrophysical Phenomena and Observations #Astrophysics #Atomic physics #Extreme ultraviolet #Galaxies: Formation, Evolution, Phenomena #Ion #Ionization #Laser #Nuclear physics #Optics #Physics #Plasma #Radiation #Stellar, planetary, and galactic studies #Ultraviolet
paper · pdf · doi:10.1086/304070
published in The Astrophysical Journal 481(2), 752-757 (IOP Publishing)
openalex publication_date 1997/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
The Seyfert 1 nucleus of NGC 3783 shows intrinsic absorption in ultraviolet (UV) resonance lines as well as in soft X-rays. We review existing measurements of these features and use them to place constraints on the physical conditions in the absorbing media. We find that the observed column densities are consistent with a single-phase, photoionized plasma responsible for absorption in both bandpasses, although alternative scenarios in which the UV and X-ray continuum sources are covered by distinct clouds are not excluded. If the UV and X-ray absorbers constitute a single medium in at least approximate ionization equilibrium with the nuclear radiation field, observed variability in the strength of absorption can be used to derive a lower bound on the absorber's electron density of n e ≳ 50 cm -3 . This result additionally implies an upper limit of about 30 pc for the separation between the nuclear continuum source and the absorbing plasma.