[O III] Equivalent Width and Orientation Effects in Quasars

The flux of the [OIII] line is considered to be a good indicator of the bolometric emission of quasars. The observed continuum emission from the accretion disc should instead be strongly dependent on the inclination angle theta between the disc axis and the line of sight. Based on this, the equivalent width (EW) of [OIII] should provide a direct measure of theta. Here we analyze the distribution of EW([OIII]) in a sample of ~6,000 SDSS quasars, and find that it can be accurately reproduced assuming a relatively small intrinsic scatter and a random distribution of inclination angles. This result has several implications: 1) it is a direct proof of the disc-like emission of the optical continuum of quasars; 2) the value of EW([OIII]) can be used as a proxy of the inclination, to correct the measured continuum emission and then estimate the bolometric luminosity of quasars; 3) the presence of almost edge-on discs among broad line quasars implies that the accretion disc is not aligned with the circumnuclear absorber, and/or that the covering fraction of the latter is rather small. Finally, we show that a similar analysis of EW distributions of broad lines (Hbeta, Mg II, C IV) provides no evidence of inclination effects, suggesting a disc-like geometry of the broad emission line region.Comment: 8 pages, 5 figures. Accepted for publication in MNRA

Mid-Infrared line diagnostics of Active Galaxies -- A spectroscopic AGN survey with ISO-SWS

We present medium resolution (R approx. 1500) ISO-SWS 2.4--45 micron spectra of a sample of 29 galaxies with active nuclei. This data set is rich in fine structure emission lines tracing the narrow line regions and (circum-)nuclear star formation regions, and it provides a coherent spectroscopic reference for future extragalactic studies in the mid-infrared. We use the data set to briefly discuss the physical conditions in the narrow line regions (density, temperature, excitation, line profiles) and to test for possible differences between AGN sub-types. Our main focus is on new tools for determining the propertibes of dusty galaxies and on the AGN-starburst connection. We present mid-IR line ratio diagrams which can be used to identify composite (starburst + AGN) sources and to distinguish between emission excited by active nuclei and emission from (circum-nuclear) star forming regions. For instance, line ratios of high to low excitation lines like [O IV]25.9um/[Ne II]12.8um, that have been used to probe for AGNs in dusty objects, can be examined in more detail and with better statistics now. In addition, we present two-dimensional diagnostic diagrams that are fully analogous to classical optical diagnostic diagrams, but better suited for objects with high extinction. Finally, we discuss correlations of mid-infrared line fluxes to the mid- and far-infrared continuum. We compare these relations to similar relations in starburst galaxies in order to examine the contribution of AGNs to the bolometric luminosities of their host galaxies. The spectra are available in electronic form from the authors.Comment: 24 pages, 23 figures, 5 tables. Accepted for A&

Black-Hole Mass and Growth Rate at High Redshift

We present new H and K bands spectroscopy of 15 high luminosity active galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained on Gemini South. We combined the data with spectra of additional 29 high-luminosity sources to obtain a sample with 10^{45.2}<\lambda L_{\lambda}(5100A)<10^{47.3} ergs/sec and black hole (BH) mass range, using reverberation mapping relationships based on the H_beta method, of 10^{8.8}-10^{10.7} M_sun. We do not find a correlation of L/L_Edd with M_BH but find a correlation with \lambda L_{\lambda}(5100A) which might be due to selection effects. The L/L_Edd distribution is broad and covers the range ~0.07-1.6, similar to what is observed in lower redshift, lower luminosity AGNs. We suggest that this consistently measured and calibrated sample gives the best representation of L/L_Edd at those redshifts and note potential discrepancies with recent theoretical and observational studies. The lower accretion rates are not in accord with growth scenarios for BHs at such redshifts and the growth times of many of the sources are longer than the age of the universe at the corresponding epochs. This suggests earlier episodes of faster growth at z>~3 for those sources. The use of the C IV method gives considerably different results and a larger scatter; this method seems to be a poor M_BH and L/L_Edd estimator at very high luminosity.Comment: 8 pages (emulateapj), 4 figures. Accepted for publication in Ap

Analyzing X-ray variability by State Space Models

In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have advantages compared with common Fourier techniques concerning their inherent stationarity and physical background. If autoregressive models are used, however, it has to be taken into account that real data always contain observational noise often obscuring the intrinsic time series of the object. We apply the technique of a Linear State Space Model which explicitly models the noise of astronomical data and allows to estimate the hidden autoregressive process. As an example, we have analysed a sample of Active Galactic Nuclei (AGN) observed with EXOSAT and found evidence for a relationship between the relaxation timescale and the spectral hardness.Comment: 4 pages, Latex, uses Kluwer Style file crckapb.cls To appear in Proc. of Astronomical Time Series, Tel Aviv, 199

Vogt-Koyanagi-Harada syndrome - current perspectives

Vogt-Koyanagi-Harada syndrome is a cause of noninfectious panuveitis, leading to significant vision loss in many patients. It is an autoimmune disease occurring in genetically susceptible individuals and clinically presents as bilateral panuveitis with serous retinal detachments and hyperemic, swollen optic discs, which are associated with neurological and auditory manifestations. Early diagnosis and prompt and adequate treatment with immunosuppressive agents (corticosteroids and other immunosuppressive drugs) may halt disease progression and prevent recurrences and vision loss. This review summarizes the current knowledge on the variable clinical aspects of this disease, highlighting diagnostic and treatment strategies

On the Signatures of Gravitational Redshift: The Onset of Relativistic Emission Lines

Aims. We quantify the effect of gravitational redshift on emission lines to explore the transition region from the Newtonian to the Einsteinian regime. With the emitting region closer to the Kerr black hole, lines are successively subjected to a stronger gravitationally induced shift and distortion. Simulated lines are compared to broad, optical emission lines observed in Mrk 110. Methods. We simulate relativistic emission line profiles by using Kerr ray tracing techniques. Emitting regions are assumed to be thin equatorial rings in stationary Keplerian rotation. The emission lines are characterised by a generalized Doppler factor or redshift associated with the line core. Results. With decreasing distance from the black hole, the gravitational redshift starts to smoothly deviate from the Newtonian Doppler factor: Shifts of the line cores reveal an effect at levels of 0.0015 to 60% at gravitational radii ranging from 10^{5} to 2. This corresponds to fully relativistic Doppler factors of 0.999985 to 0.4048. The intrinsic line shape distortion by strong gravity i.e. very asymmetric lines occur at radii smaller than roughly ten gravitational radii. Conclusions. Due to the asymptotical flatness of black hole space-time, GR effects are ubiquitous and their onset can be tested observationally with sufficient spectral resolution. With a resolving power of ~100000, yielding a resolution of ~0.1 Angstroems for optical and near-infrared broad emission lines like H\beta, HeII and Pa\alpha, the gravitational redshift can be probed out to approximately 75000 gravitational radii. [abridged]Comment: 9 pages, 9 figures, accepted for publication in A&

A Single Intrinsic Luminosity Function for Both Type-I and Type-II Active Galactic Nuclei

The luminous electromagnetic emission from distant active galactic nuclei (AGNs) including quasars is believed to be powered by accretion onto super-massive black holes (SMBHs). In the standard unification model for AGNs a dusty torus covers a significant portion of the viewing angles to the accretion disk and the BH. The system is classified as a type-I AGN if the accretion disk is viewed through the opening part; otherwise it is called a type-II AGN. Therefore the ratio of type-II to type-I AGNs serves as a sensitive probe to the unification model. A surprising discovery made from several large sky coverage and/or deep AGN surveys has found a significant anti-correlation between the type-II fraction and the observed X-ray luminosity between 2-10 keV. This suggests two different luminosity functions for the two types of AGNs, thus challenging the AGN unification model. However this observed anti-correlation is a natural consequence of the AGN unification model with only one intrinsic luminosity function if the inclination angle effects of the X-ray emitting accretion disk are taken into account. Thus the AGN unification model survived another critical test.Comment: 10 pages, 2 figures, submitted on 2004 Oct. 20 and accepted on 2004 Dec. 1 for publication in ApJ Letter

XMM-Newton RGS observation of the warm absorber in Mrk 279

The Seyfert 1 galaxy Mrk 279 was observed by XMM-Newton in November 2005 in three consecutive orbits, showing significant short-scale variability (average soft band variation in flux ~20%). The source is known to host a two-component warm absorber with distinct ionisation states from a previous Chandra observation. We aim to study the warm absorber in Mrk 279 and investigate any possible response to the short-term variations of the ionising flux, and to assess whether it has varied on a long-term time scale with respect to the Chandra observation. We find no significant changes in the warm absorber on neither short time scales (~2 days) nor at longer time scales (two and a half years), as the variations in the ionic column densities of the most relevant elements are below the 90% confidence level. The variations could still be present but are statistically undetected given the signal-to-noise ratio of the data. Starting from reasonable standard assumptions we estimate the location of the absorbing gas, which is likely to be associated with the putative dusty torus rather than with the Broad Line Region if the outflowing gas is moving at the escape velocity or larger.Comment: 10 pages, 9 figures, 6 tables. Accepted for publication in Astronomy & Astrophysic