Ari Laor

Dust in the narrow-line region of active galactic nuclei

Observations of active galactic nuclei (AGNs) show the presence of a cloud system with two well-separated regions of line emission, the narrow-line region (NLR) and the broad-line region (BLR). There are several unexplained features of the system. First, there is an apparent gap between the BLR and the NLR with almost no line emission. Second, the covering factor of the NLR clouds, as inferred from photoionization models, is an order of magnitude smaller than the covering factor of the BLR, but the observed infrared continuum and new high-resolution HST images suggest a much larger covering factor. Finally the BLR size scales with the source luminosity in a way which is not understood

High-rate active galaxy monitoring at the wise observatory. III, The broad-line region of NGC 4151

Results of an AGN monitoring program for the Seyfert galaxy NGC 4151 are presented. The space and velocity distribution of the broad large region (BLR) gas in this AGN are analyzed. Through cross-correlation, it is found that both Hα and Hβ lag the continuum variations by 9 ± 12 days. Through Fourier and maximun entropy deconvolutions of the continuum and emission-line curves, the approximate transfert function of the BLR in this object is recovered.

Type 1 low z AGN. I. Emission properties

We analyse the emission properties of a new sample of 3579 type 1 AGN, selected from Sloan Digital Sky Survey (SDSS) Data Release 7 based on the detection of broad Hα emission. The sample extends over a broad Hα luminosity LbHα of and a broad Hα full width at half-maximum (FWHM) of , which covers the range of black hole mass 106 < MBH/M⊙ < 109.5 and luminosity in Eddington units 10−3 < L/LEdd < 1. We combine ROSAT, GALEX and 2MASS observations to form the spectral energy distribution (SED) from 2.2 xa0m to 2 keV. We find the following. (1) The distribution of the Hα FWHM values is independent of luminosity. (2) The observed mean optical–ultraviolet (optical–UV) SED is well matched by a fixed-shape SED of luminous quasars, which scales linearly with LbHα, and a host galaxy contribution. (3) The host galaxy r-band (fibre) luminosity function follows well the luminosity function of inactive non-emission-line galaxies (NEGs), consistent with a fixed fraction of ∼3 perxa0cent of NEGs hosting an AGN, regardless of the host luminosity. (4) The hosts of lower luminosity AGN have a mean z-band luminosity and u−z colour which are identical to NEGs with the same redshift distribution. With increasing LbHα the AGN hosts become bluer and less luminous than NEGs. The implied increasing star formation rate with LbHα is consistent with the relation for SDSS type 2 AGN of similar bolometric luminosity. (5) The optical–UV SED of the more luminous AGN shows a small dispersion, consistent with dust reddening of a blue SED, as expected for thermal thin accretion disc emission. (6) There is a rather tight relation between and LbHα, which provides a useful probe for unobscured (true) type 2 AGN. (7) The primary parameter that drives the X-ray to UV emission ratio is luminosity, rather than MBH or L/LEdd.

High-rate spectroscopic active galactic nucleus monitoring at the Wise Observatory. I. Markarian 279

Spectrophotometric monitoring of a sample of AGNs has achieved a temporal sampling rate of once every 3-4 days, over a period of 5-7 months. By observing each object simultaneously with a nearby field star, in a long-slit spectroscopy mode, accurate flux measurements were obtained even during bad weather and full moon. Results for the Seyfert 1 galaxy MrK 279 are discussed. This object brightened by 20-50 percent in H-alpha, H-beta, and the optical continuum during the period of observation. The high sampling rate and small error allow the determination, through cross-correlation, of the lag in the emission-line response to the continuum brightening. A lag of 12 days is observed. The size of the broadline region (BLR) is estimated to be 12 + or - 3 light days in this object; the results rule out, at the 95 percent significance level, a BLR of 21 light-days or larger. This result is in conflict with the standard photoionization model of AGNs, which predicts a BLR size larger by an order of magnitude. 27 refs.

High-rate spectroscopic active galactic nucleus monitoring at the wise observatory. II: NGC 5548

Les observations spectroscopiques de la galaxie de Seyfert de type 1, NGC 5548, sont analysees. Les fonctions de correlation croisee entre le continuum et les raies Hα et Hβ sont etudiees. La taille de la region de raies larges est determinee

Erratum: “Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass” (ApJ, 632, 799 [2005])

In the original version of this paper, we reported on a series of ultraviolet (UV) spectroscopic observations of the dwarf Seyfert 1 galaxy NGC4395,madewith the Space Telescope Imaging Spectrograph on theHubble Space Telescope (HST ). Unfortunately, a data processing error led to an incorrect flux calibration for these spectra. All STIS-based UV fluxes in the original paper are too high by a factor of 7.96 as a result of neglecting to adjust the flux-scaling algorithm from a diffuse source to a point source. Because most of the analysis in the original paper involved only relative flux changes, most of the scientific conclusions are unaffected by this correction, except for the slope of the broad-line region radius–luminosity relationship, as described below. Specific changes that result from this correction are:

Dust inflated accretion disc as the origin of the broad line region in active galactic nuclei

The Broad Line Region (BLR) in AGN is composed of dense gas (

Massive thin accretion discs – I. Calculated spectra

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Massive thin accretion discs. II: Polarization

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Supernova PTF12glz: a possible shock breakout driven through an aspherical wind

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