Monitoring of the optical and 2.5-11.7 mu m spectrum and mid-IR imaging of the Seyfert 1 galaxy Mrk 279 with ISO
European Space Research and Technology Centre1, European Southern Observatory2, Harvard University3, University of Arizona4, Ohio State University5, Goddard Space Flight Center6, University of Leicester7, Tel Aviv University8, University of St Andrews9, Space Telescope Science Institute10, Johns Hopkins University11, University of California, Los Angeles12, Isaac Newton Institute13, Shanghai Astronomical Observatory14, European University of Madrid15
01 Apr 2001-Vol. 369, Iss: 1, pp 57-64
TL;DR: In this article, mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO satellite are presented together with the results of a one-year monitoring campaign of the 2.5-11.7 mum spectrum.
Abstract: Mid-infrared images of the Seyfert 1 galaxy Mrk 279 obtained with the ISO satellite are presented together with the results of a one-year monitoring campaign of the 2.5-11.7 mum spectrum. Contemporaneous optical photometric and spectrophotometric observations are also presented. The galaxy appears as a point-like source at the resolution of the ISOCAM instrument (4-5 "). The 2.5-11.7 mum average spectrum of the nucleus in Mrk 279 shows a strong power law continuum with alpha = -0.80 +/- 0.05 (F nu proportional to nu (alpha)) and weak PAK emission features. The Mrk 279 spectral energy distribution shows a mid-IR bump, which extends from 2 to 15-20 mum The mid-IR bump is consistent with thermal emission from dust grains at a distance of greater than or similar to 100 It-d. No significant variations of the mid-IR flux have been detected during our observing campaign, consistent with the relatively low amplitude (similar to 10% rms) of the optical variability during the campaign. The time delay for H beta line emission in response to the optical continuum variations is tau = 16.7(-5.6)(+5.3), days, consistent with previous measurements.
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TL;DR: In this article, a reanalysis of broad emission-line reverberation-mapping data was carried out for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis, and it was shown that the highest precision measure of the virial product cτΔV2/G is obtained by using the cross-correlation function centroid (cf.
Abstract: 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 cτΔV2/G, where τ is the emission-line lag relative to continuum variations and ΔV 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 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 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 reverberation-based 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
1,893 citations
Cites methods from "Monitoring of the optical and 2.5-1..."
...We examined two completely independent sets of data, one from theWise Observatory program in 1988 (Maoz et al. 1990) and one from an International AGN Watch project in 1996 (Santos-Lleó et al. 2001)....
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Georgia State University1, Niels Bohr Institute2, Ohio State University3, University of California, Irvine4, University of Arizona5, California Polytechnic State University6, University of California, Riverside7, University of California, Berkeley8, Princeton University9, University of California, Los Angeles10, California Institute of Technology11, University of California, Santa Barbara12, Seoul National University13
TL;DR: In this article, the authors present an updated and revised analysis of the relationship between the H{beta} broadline region (BLR) radius and the luminosity of the active galactic nucleus (AGN).
Abstract: We present an updated and revised analysis of the relationship between the H{beta} broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create ''AGN-free'' images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the H{beta} time lag, which is assumed to yield the average H{beta} BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R{sub BLR}-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of {alpha}= 0.533{sup +0.035}{sub -0.033}, consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19more » {+-} 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R{sub BLR}-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts.« less
795 citations
TL;DR: In this article, a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates, was used to estimate the characteristic timescale and amplitude of flux variations; their approach is not affected by biases introduced from discrete sampling effects.
Abstract: We analyze a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z < 2.8, 1042 λL λ(5100 A) 1046, and 106 M BH/M ☉ 1010. We model the light curves as a continuous time stochastic process, providing a natural means of estimating the characteristic timescale and amplitude of quasar variations. We employ a Bayesian approach to estimate the characteristic timescale and amplitude of flux variations; our approach is not affected by biases introduced from discrete sampling effects. We find that the characteristic timescales strongly correlate with black hole mass and luminosity, and are consistent with disk orbital or thermal timescales. In addition, the amplitude of short-timescale variations is significantly anticorrelated with black hole mass and luminosity. We interpret the optical flux fluctuations as resulting from thermal fluctuations that are driven by an underlying stochastic process, such as a turbulent magnetic field. In addition, the intranight variations in optical flux implied by our empirical model are 0.02 mag, consistent with current microvariability observations of radio-quiet quasars. Our stochastic model is therefore able to unify both long- and short-timescale optical variations in radio-quiet quasars as resulting from the same underlying process, while radio-loud quasars have an additional variability component that operates on timescales 1 day.
670 citations
TL;DR: In this paper, the authors presented high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which they have modeled to create a nucleus-free image of each AGN host galaxy.
Abstract: We present high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to ground-based spectroscopic luminosity measurements at 5100 A. After correcting the luminosities of the AGNs for the contribution from starlight, we re-examine the Hβ R BLR-L relationship. Our best fit for the relationship gives a power-law slope of 0.52 with a range of 0.45-0.59 allowed by the uncertainties. This is consistent with our previous findings, and thus still consistent with the naive assumption that all AGNs are simply luminosity-scaled versions of each other. We discuss various consistency checks relating to the galaxy modeling and starlight contributions, as well as possible systematic errors in the current set of reverberation measurements from which we determine the form of the R BLR-L relationship.
646 citations
Cites result from "Monitoring of the optical and 2.5-1..."
...We include here only the results for Mrk 279 reported by Santos-Lleó et al. (2001)....
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TL;DR: In this article, the authors measured the host-galaxy starlight contribution to the continuum luminosity at 5100? through the typical ground-based slit position and geometry used in the reverberation-mapping campaigns.
Abstract: We have obtained high-resolution images of the central regions of 14 reverberation-mapped active galactic nuclei (AGNs) using the Hubble Space Telescope Advanced Camera for Surveys High Resolution Camera to account for host-galaxy starlight contamination of measured AGN luminosities. We measure the host-galaxy starlight contribution to the continuum luminosity at 5100 ? through the typical ground-based slit position and geometry used in the reverberation-mapping 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 AGNs. We find the power-law slope of the relationship for the H? line to be 0.518 ? 0.039, shallower than what was previously reported and consistent with the slope of 0.5 expected from the naive theoretical assumption that all AGNs have, on average, the same ionizing spectrum and the same ionization parameter and gas density in the H? line-emitting region.
476 citations
References
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TL;DR: In this paper, a model-independent method of assessing the uncertainties in cross-correlation lags determined from the light curves of active galactic nuclei (AGNs) was proposed.
Abstract: We describe a model-independent method of assessing the uncertainties in cross-correlation lags determined from the light curves of active galactic nuclei (AGNs) and use this method to investigate the reality of lags between UV and optical continuum variations in well-studied AGNs. Our results confirm the existence of such lags in NGC 7469. We find that the continuum variations at 1825, 4845, and 6962 A follow those at 1315 A by , and days, respectively, based on the centroids of the cross-correlation functions; the error intervals quoted correspond to 68% confidence levels, and each of these lags is greater than zero at no less than 97% confidence. We do not find statistically significant interband continuum lags in NGC 5548, NGC 3783, or Fairall 9. Wavelength-dependent continuum lags may be marginally detected in the case of NGC 4151. However, on the basis of theoretical considerations, wavelength-dependent continuum lags in sources other than NGC 7469 are not expected to have been detectable in previous experiments. We also confirm the existence of a statistically significant lag between X-ray and UV continuum variations in the blazar PKS 2155–304.
543 citations
"Monitoring of the optical and 2.5-1..." refers methods in this paper
...Uncertainties were estimated using the model-independent FR/RSS Monte-Carlo method described by Peterson et al. (1998)....
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TL;DR: In this article, the authors used a 2D radiative transfer algorithm to calculate the thermally reradiated infrared spectra of the compact dust tori which are thought to surround many AGN.
Abstract: Using a new 2D radiative transfer algorithm, we have calculated the thermally reradiated infrared spectra of the compact dust tori which are thought to surround many AGN. These tori radiate anisotropically. Face-on tori may be from one-half to a few orders of magnitude brighter than edge-on tori throughout the infrared. Their spectra at nearly all viewing angles are basically 'bumps' which are about 50 percent wider than blackbodies and peak in the mid-infrared at a wavelength determined mainly by the flux of nuclear radiation on the inner edge of the torus. The infrared color temperatures are hotter for face-on tori than edge-on tori by about 100 K. The 10 micron silicate feature often associated with dust can appear in absorption, emission, or not at all. There is a rough tendency for absorption features to be more prominent for edge-on tori than for face-on tori.
528 citations
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...Though a detailed quantitative fit with a particular model is beyond the scope of this paper, it is nevertheless illustrative to perform a qualitative comparison of our data with the theoretical predictions from the torus model by Pier & Krolik (1992)....
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...In the Pier & Krolik (1992) model, the torus emission is expected to peak at a wavelength λpeak that depends primarily on the flux illuminating the torus inner surface and its inclination angle i with respect to the line of sight....
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...5 of Pier & Krolik (1992) also suggests a moderately thick torus, with rin/h = 0.3....
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TL;DR: In this paper, two separate cross-correlation methdologies, the interpolation method of Gaskell and Sparkle and the discrete correlation function of Edelson and Krolik, were used to quantify the lags between continuum and emission-line flux variations in active galactic nuclei.
Abstract: We discuss two separate cross-correlation methdologies, the interpolation method of Gaskell and Sparkle and the discrete correlation function of Edelson and Krolik, that are commonly used to quantify the lags between continuum and emission-line flux variations in active galactic nuclei (AGNs). We show that if similar assumptions are made to normalize the cross-correlation functions, the two methods are in good agreement for well-sampled AGN light curves. We also investigate the performance of cross-correlation methodology for less well-sampled data sets through Monte Carlo simulations that employ realistic models of the continuum behavior (based on well-observed Seyfert galaxies) and typical emission-line response times. We find that the interpolation method fairly accurately recovers the emission-line lags as the sampling is degraded (i.e., as the number of observed points is reduced). We find that for the cases investigated, the emission-line lags can be determined with reasonable accuracy even with mean sampling intervals as large as around two weeks.
344 citations
"Monitoring of the optical and 2.5-1..." refers methods in this paper
...We used both the interpolation method of Gaskell & Sparke (1986) and the discretecorrelation function (DCF) method of Edelson & Krolik (1988), in both cases employing the specific implementation described by White & Peterson (1994)....
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TL;DR: In this paper, the size of broad-line regions in three well-studied Seyfert I galaxies are presented, and differences between these and previously reported size estimates for NGC 4151 are discussed.
Abstract: Quantitative estimates of the sizes of broad-line regions in three well-studied Seyfert I galaxies are presented, and differences between these and previously reported size estimates for NGC 4151 are discussed. Both Lick Observatory and IUE satellite data on NGC 4151 are analyzed, and it is shown that both are consistent with the high-ionization filaments (those emitting C IV, He II, and the high-order Balmer lines) mostly lying about 5 lt-day from the central source. The low-ionization filaments are 3 or 4 times further out. The Ohio State data on Akn 120 show the H-beta emitting region to be about 6 lt-day from the central source, and IUE data suggest that the Ly-alpha region in Mrk 509 is about 10 lt-day out. The present results imply that the densities in broad-line regions are a couple of orders of magnitude higher than in current standard models. For the objects studied here, the light crossing times are of the same order of magnitude as the continuum variability time scales, so kinematic mapping of the broad-line regions will be extremely difficult. 56 references.
333 citations
"Monitoring of the optical and 2.5-1..." refers methods in this paper
...We used both the interpolation method of Gaskell & Sparke (1986) and the discretecorrelation function (DCF) method of Edelson & Krolik (1988), in both cases employing the specific implementation described by White & Peterson (1994)....
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TL;DR: In this article, Lockman et al. presented integrated Galactic 21-cm column densities toward about 174 quasars and AGN and corrected for stray radiation, using the technique of Lockman this article.
Abstract: Integrated Galactic 21-cm column densities toward about 174 quasars and AGN are presented. The data are corrected for stray radiation, using the technique of Lockman et al. (1986). Because of the 21-arcmin beam size of the 140-ft telescope used in the study, the uncertainty in N(H) due to angular variations in the H I of the Galaxy at high latitudes is minimized. The column densities are accurate to about 1 X 10 to the 19th atoms/sq cm, or 5 percent, whichever is larger. Errors above N(H) of about 4 X 10 to the 20th atoms/sq cm are dominated by opacity uncertainties.
242 citations
"Monitoring of the optical and 2.5-1..." refers methods in this paper
...It has been corrected for foreground reddening using NH = 1.6 1020 cm−2 (Elvis et al. 1989)....
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