On the Baldwin Effect in Active Galactic Nuclei: I. The Continuum-Spectrum - Mass Relationship

We suggest that the Baldwin Effect is a result of the spectral dependence of the line-driving ionizing continuum on the black hole mass. We derive a relationship between the mass of the central black hole and the broad emission line luminosity in active galactic nuclei (AGN). Assuming the UV spectrum of AGN is emitted from an optically thick medium we find an expression for the characteristic energy of the ``UV bump'' in terms of the observable luminosity and emission-line width. We show empirically and analytically that the bump energy is anti-correlated with the black-hole mass and with the continuum luminosity. Our model reproduces the observed inverse correlation between equivalent width and continuum luminosity, yielding an explanation of the Baldwin effect from first principles. The model gives a good fit to the Baldwin Effect of the CIV line for a mean quasar EUV spectrum (Zheng et al. 1997) and for several model spectra. The model also predicts a correlation between the strength of the Baldwin Effect (the slope of the equivalent width as a function of luminosity) and the ionization potential, consistent with recent data.Comment: 19 pages Latex, 2 figures. Accepted for publication in the Astrophysical Journa

Far-Ultraviolet Observations of NGC 3516 using the Hopkins Ultraviolet Telescope

We observed the Seyfert 1 galaxy NGC 3516 twice during the flight of Astro-2 using the Hopkins Ultraviolet Telescope in March 1995. Simultaneous X-ray observations were performed with ASCA. Our far-ultraviolet spectra cover the spectral range 820-1840 A with a resolution of 2-4 A. No significant variations were found between the two observations. The total spectrum shows a red continuum, $f_\nu \sim \nu^{-1.89}$, with an observed flux of $\rm 2.2 \times 10^{-14}~erg~cm^{-2}~s^{-1}~\AA^{-1}$ at 1450 A, slightly above the historical mean. Intrinsic absorption in Lyman $\beta$ is visible as well as absorption from O~vi 1032,1038, N~v 1239,1243, Si~iv 1394,1403, and C~iv 1548,1551. The UV absorption lines are far weaker than is usual for NGC~3516, and also lie closer to the emission line redshift rather than showing the blueshift typical of these lines when they are strong. The neutral hydrogen absorption, however, is blueshifted by $400~\rm km~s^{-1}$ relative to the systemic velocity, and it is opaque at the Lyman limit. The sharpness of the cutoff indicates a low effective Doppler parameter, $b < \rm 20~km~s^{-1}$. For $b = \rm 10~km~s^{-1}$ the derived intrinsic column is $\rm 3.5 \times 10^{17}~cm^{-2}$. As in NGC~4151, a single warm absorber cannot produce the strong absorption visible over the wide range of observed ionization states. Matching both the UV and X-ray absorption simultaneously requires absorbers spanning a range of $10^3$ in both ionization parameter and column density.Comment: 18 pages, 4 PostScript figures, uses aaspp4.sty To appear in the August 20, 1996, issue of The Astrophysical Journa

The rise of an ionized wind in the Narrow Line Seyfert 1 Galaxy Mrk 335 observed by XMM-Newton and HST

We present the discovery of an outflowing ionized wind in the Seyfert 1 Galaxy Mrk 335. Despite having been extensively observed by most of the largest X-ray observatories in the last decade, this bright source was not known to host warm absorber gas until recent XMM-Newton observations in combination with a long-term Swift monitoring program have shown extreme flux and spectral variability. High resolution spectra obtained by the XMM-Newton RGS detector reveal that the wind consists of three distinct ionization components, all outflowing at a velocity of 5000 km/s. This wind is clearly revealed when the source is observed at an intermediate flux state (2-5e-12 ergs cm^-2 s^-1). The analysis of multi-epoch RGS spectra allowed us to compare the absorber properties at three very different flux states of the source. No correlation between the warm absorber variability and the X-ray flux has been determined. The two higher ionization components of the gas may be consistent with photoionization equilibrium, but we can exclude this for the only ionization component that is consistently present in all flux states (log(xi)~1.8). We have included archival, non-simultaneous UV data from HST (FOS, STIS, COS) with the aim of searching for any signature of absorption in this source that so far was known for being absorption-free in the UV band. In the COS spectra obtained a few months after the X-ray observations we found broad absorption in CIV lines intrinsic to the AGN and blueshifted by a velocity roughly comparable to the X-ray outflow. The global behavior of the gas in both bands can be explained by variation of the covering factor and/or column density, possibly due to transverse motion of absorbing clouds moving out of the line of sight at Broad Line Region scale.Comment: 24 pages, 12 figures, ApJ accepte