C IV and C III] Reverberation Mapping of the Luminous Quasar PG 1247+267

Astronomy and Astrophysics, 2006

Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberation-mapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty. Methods. We characterize the broad Hβ emission-line profiles by the ratio of their full-width at half maximum (FWHM) to their line dispersion, i.e., the second moment of the line profile. We use this parameter to separate the reverberation-mapped AGNs into two populations, the first with narrower Hβ lines that tend to have relatively extended wings, and the second with broader lines that are relatively flat-topped. The first population is characterized by higher Eddington ratios than the second. Within each population, we calibrate the black-hole mass scale by comparison of the reverberation-based mass with that predicted by the bulge velocity dispersion. We also use the distribution of ratios of the reverberation-based mass to the velocity-dispersion mass prediction in a comparison with a "generalized thick disk" model in order to see if inclination can plausibly account for the observed distribution. Results. We find that the line dispersion is a less biased parameter in general than FWHM for black hole mass estimation, although we show that it is possible to empirically correct for the bias introduced by using FWHM to characterize the emissionline width. We also argue that inclination effects are apparent only in some small subset of the reverberation-based mass measurements; it is primarily the objects with the narrowest emission lines that seem to be most strongly affected. Conclusions. Our principal conclusion is that the Hβ profile is sensitive primarily to Eddington ratio, but that inclination effects play a role in some cases.

The Astrophysical Journal, 2006

We have obtained high resolution images of the central regions of 14 reverberation-mapped active galactic nuclei (AGN) using the Hubble Space Telescope Advanced Camera for Surveys High Resolution Camera to account for hostgalaxy starlight contamination of measured AGN luminosities. We measure the host-galaxy starlight contribution to the continuum luminosity at 5100Å through the typical ground-based slit position and geometry used in the reverberationmapping campaigns. We find that removing the starlight contribution results in a significant correction to the luminosity of each AGN, both for lower luminosity sources, as expected, but also for the higher luminosity sources such as the PG quasars. After accounting for the host galaxy starlight, we revisit the well-known broad-line region radius-luminosity relationship for nearby AGN. We find the power-law slope of the relationship for the Hβ line to be 0.518 ± 0.039, shallower than previously reported and consistent with the slope of 0.5 expected from the naive theoretical assumption that all AGN have, on average, the same ionizing spectrum and the same ionization parameter and gas density in the Hβ line-emitting region.

Monthly Notices of the Royal Astronomical Society, 1996

We describe six years of a Band R monitoring program of a sample of 44 radio-loud quasars. The observations were performed at the Wise Observatory, Cerro Tololo Interamerican Observatory and McDonald Observatory with a mean sampling of about 4-8 times a year and a typical accuracy of 0.02-0.03 mag. We show the B, R and B -R light-curves of all sources and discuss the sample properties in terms of variability amplitude, luminosity, continuum shape, radio structure and variability time-scale. All objects in our sample have varied during the monitoring campaign. In 15 per cent of the sources the variability is smaller than 0.2 mag and in 45 per cent between 0.2 and 0.4 mag. The amplitude of the variations does not depend on redshift or luminosity. Furthermore, there is no difference, in this respect, between core-dominated and lobe-dominated sources. Our sampling is adequate to calculate the autocorrelation function of 34 sources in the sample and to use it to define the typical variability time-scale. We find that the rest-frame variability time is inversely correlated with the source luminosity. However, external effects caused by the sampling period and the frequency can strongly influence this conclusion and we suggest ways to try to eliminate such biases. If correct, the inverse correlation with luminosity can dominate any cosmological (1 +z) dependence.

The Astrophysical Journal, 2004

We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple line measurements, we find that the highest precision measure of the virial product cÁV 2 =G, where is the emission-line lag relative to continuum variations and ÁV is the emission-line width, is obtained by using the cross-correlation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to FWHM) for the line width and by measuring the line width in the variable part of the spectrum. Accurate line-width measurement depends critically on avoiding contaminating features, in particular the narrow components of the emission lines. We find that the precision (or random component of the error) of reverberationbased black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods. Based on results presented in a companion paper by Onken et al., we provide a zero-point calibration for the reverberation-based black hole mass scale by using the relationship between black hole mass and host-galaxy bulge velocity dispersion. The scatter around this relationship implies that the typical systematic uncertainties in reverberationbased black hole masses are smaller than a factor of 3. We present a preliminary version of a mass-luminosity relationship that is much better defined than any previous attempt. Scatter about the mass-luminosity relationship for these AGNs appears to be real and could be correlated with either Eddington ratio or object inclination.

2001

Abstract We present new high signal-to-noise ratio spectra of the components B and C of the gravitational lensing system MG 2016+ 112. We show that image C displays strong emission lines of Ly $\ alpha $, NV, CIV, HeII, and CIII] redshifted to z= 3.27, similar to images A and B. We examine the emission-line flux ratios in order to put constraints on the lens models as well as to investigate the intrinsic nature of MG 2016+ 112.

The Astrophysical Journal, 1999

We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple line measurements, we find that the highest precision measure of the virial product cτ ∆V 2 /G, where τ is the emission-line lag relative to continuum variations and ∆V is the emission-line width, is obtained by using the crosscorrelation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to full width half maximum) for the line width and by measuring the line width in the variable part of the spectrum. Accurate line-width measurement depends critically on avoiding contaminating features, in particular the narrow components of the emission lines. We find that the precision (or random component of the error) of reverberation-based black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods. Based on results

The Astrophysical Journal, 2010

We investigate the characteristic radiative efficiency ǫ, Eddington ratio λ, and duty cycle P 0 of high-redshift active galactic nuclei (AGN), drawing on measurements of the AGN luminosity function at z = 3 -6 and, especially, on recent measurements of quasar clustering at z = 3 -4.5 from the Sloan Digital Sky Survey. The free parameters of our models are ǫ, λ, and the normalization, scatter, and redshift evolution of the relation between black hole mass M BH and halo virial velocity V vir . We compute the luminosity function from the implied growth of the black hole mass function and the quasar correlation length from the bias of the host halos. We test our adopted formulae for the halo mass function and halo bias against measurements from the large N-body simulation developed by the MICE collaboration. The strong clustering of AGNs observed at z = 3 and, especially, at z = 4 implies that massive black holes reside in rare, massive dark matter halos. Reproducing the observed luminosity function then requires high efficiency ǫ and/or low Eddington ratio λ, with a lower limit (based on 2σ agreement with the measured z = 4 correlation length) ǫ 0.7λ/(1 + 0.7λ), implying ǫ 0.17 for λ > 0.25. Successful models predict high duty cycles, P 0 ∼ 0.2, 0.5, and 0.9 at z = 3.1, 4.5 and 6, respectively, and they require that the fraction of halo baryons locked in the central black hole is much larger than the locally observed value. The rapid drop in the abundance of the massive and rare host halos at z > 7 implies a proportionally rapid decline in the number density of luminous quasars, much stronger than simple extrapolations of the z = 3 -6 luminosity function would predict. For example, our most successful model predicts that the highest redshift quasar in the sky with true bolometric luminosity L > 10 47.5 erg s -1 should be at z ∼ 7.5, and that all quasars with higher apparent luminosities would have to be magnified by lensing.

The Astrophysical Journal, 1973

The luminosity function of quasars and its evolution are discussed, based on comparison of available data on optically selected quasars and quasars found in radio catalogs. It is assumed that the redshift of quasars is cosmological and the results are expressed in the framework of the A = 0, qo = 1 cosmological model. The predictions of various density evolution laws are compared with observations of an optically selected sample of quasars and quasarsamples from radio catalogs. The differences between the optical luminosity functions, the redshift distributions and the radio to optical luminosity ratios of optically selected quasars and radio quasars rule out luminosity functions where there is complete absence of correlation between radio and optical luminosities. These differences also imply that Schmidt's (1970) luminosity function, where there exists a statistical correlation between radio and optical luminosities, although may be correct for high redshift objects, disagrees with observation at low redshifts. These differences can be accounted for by postulating existence of two classes (I and II) of objects. The class I non-evolving objects dominate the optically selected samples at low redshifts, have low optical luminosities of about 10 w/Hz (at 2500 A) and are absent from radio samples because of their relative low radio to optical luminosity ratios. The class II objects are the quasars found in radio catalogs, show strong evolution, have optical luminosities of 1023 to 10 24w/Hz and dominate the optically selected samples at large redshifts. Possible relations between the two classes are also discussed, and tests for the validity of this picture are presented.

Using a sample of optically-selected quasars from the Sloan Digital Sky Survey, we have determined the radio-loud fraction (RLF) of quasars as a function of redshift and optical luminosity. The sample contains more than 30,000 objects and spans a redshift range of 0 < z 5 and a luminosity range of −30 M i < −22. We use both the radio-to-optical flux ratio (R parameter) and radio luminosity to define radio-loud quasars. After breaking the correlation between redshift and luminosity due to the flux-limited nature of the sample, we find that the RLF of quasars decreases with increasing redshift and decreasing luminosity. The relation can be described in the form of log(RLF/(1-RLF)) = b 0 +b z log(1+z)+b M (M 2500 +26), where M 2500 is the absolute magnitude at restframe 2500Å, and b z , b M < 0. When using R > 10 to define radio-loud quasars, we find that b 0 = −0.132 ± 0.116, b z = −2.052 ± 0.261, and b M = −0.183 ± 0.025. The RLF at z = 0.5 declines from 24.3% to 5.6% as luminosity decreases from M 2500 = −26 to M 2500 = −22, and the RLF at M 2500 = −26 declines from 24.3% to 4.1% as redshift increases from 0.5 to 3, suggesting that the RLF is a strong function of both redshift and luminosity. We also examine the impact of fluxrelated selection effects on the RLF determination using a series of tests, and find that the dependence of the RLF on redshift and luminosity is highly likely to be physical, and the selection effects we considered are not responsible for the dependence.

2005

We present a technique for the successive restoration of the branches of the one-dimensional strip brightness distribution across a quasar&#x27;s accretion disk via the analysis of observations of high magnification events in measured fluxes from the multiple quasar images produced by a gravitational lens. Hypothesizing these events to by associated with microlensing by a fold caustic, the branches of brightness distribution are searched for on compact sets of non-negative, monotonically non-increasing, convex downward functions. The results of numerical simulations show that the solution obtained is stable against random noise. Analysis of the light curves of high magnification events in the fluxes from components C and A of the gravitational lens QSO 2237+0305, observed by the OGLE and GLITP groups, has yielded the forms of the strip brightness distributions across the accretion disk of the lensed quasar. The resulting sizes of the accretion disk are in agreement with results obta...