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Journal ArticleDOI

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

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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Citations
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Journal ArticleDOI
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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Journal ArticleDOI
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

Journal ArticleDOI
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

Journal ArticleDOI
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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Journal ArticleDOI
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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Journal ArticleDOI
TL;DR: In this article, the authors present both high-resolution and low-resolution (R = 1260) J-band spectra of a sample of 15 Seyfert 2 galaxies.
Abstract: We present both high-resolution (R = 1260) and low-resolution (R = 345 and 425) J-band spectra of a sample of 15 Seyfert 2 galaxies. Our goal is to look for broad Pa beta lines, indicating broad-line regions which are hidden by dust from our view at optical wavelengths. Of the 15 objects studied here, three have broad Pa beta lines: MCG-05.23.16, Mrk 463E, and NGC 2992. Mrk 176 and NGC 5728 may also have weak broad lines. In NGC 5506, previously reported to have broad Pa beta and hydrogen alpha lines, we find that the Pa beta line profile is continuous and has the same shape as the nearby line (Fe II) lambda 1.2567, which should not have a broad component. We interpret these observations as gas from the narrow-line region (NLR) with no broad component. In NGC 5506, however, the NLR profiles become broader with increasing wavelength, indicating that highly reddened wings are becoming more readily visible at the longer wavelengths. We confirm the correlation of (O I) lambda 6300/hydrogen alpha and (Fe II) lambda 1.644/Br gamma (the latter transformed to (Fe II) lambda 1.2567/Pa beta to compare with our data) found by previous authors when comparing active galactic nuclei (AGNs), supernova remnants, starbursts, and H II regions. The correlation confirms that in all of these objects both (O I) lambda 6300 and the (Fe II) lines come from partially ionized regions in which hydrogen is mostly neutral. Comparison of the infrared optical depths with column depths determined from X-ray data show a general tendency for the objects with detected broad Pa beta to have lower X-ray columns.

239 citations

Journal ArticleDOI

168 citations


"Monitoring of the optical and 2.5-1..." refers background in this paper

  • ...Indeed, a faint extended nebulosity is apparent in the K-band (∼2.2µm) image of McLeod & Rieke (1995)....

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  • ...In the K-band, McLeod & Rieke (1995) estimated that the AGN contributes 90% of the flux within the central 1....

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Journal ArticleDOI
TL;DR: In this article, it was shown that the Mg II 2800 line emissivity depends primarily on the density of soft X-ray photons, as postulated in optically thick photoionization models of the broad-line region (BLR) gas.
Abstract: The Seyfert galaxy Fairall 9 (F9) has been observed in the far-UV and optical range with the IUE, and at 27 different epochs at J, H, K, and L. The UV continuum underwent dramatic variations, its intensity decreasing by a factor 33 from a maximum in 1978 to a deep minimum in mid-1984. The near-IR and optical fluxes changed by a factor of about three and in the same sense as the UV. The K and L emission are interpreted as thermal radiation from dust lying at about 1 lt-yr from the UV source. The Ly-alpha 1216, C IV 1550, and Mg II 2800 emission-line intensities also vary in the same sense as the UV continuum but with a lag of 155 + or - 45 days. This strongly suggests that the broad-line region (BLR) gas is photoionized and lies inside the dust shell. Strong evidence is presented that the Mg II 2800 line emissivity depends primarily on the density of soft X-ray photons, as postulated in optically thick photoionization models of the BLR. 59 references.

157 citations


"Monitoring of the optical and 2.5-1..." refers background or methods in this paper

  • ...Assuming “normal” near-IR colors (K−L = 0.22±0.02mag; Clavel et al. 1989) for the stellar population, we derive a total host-galaxy flux of 18 mJy at 3.5µm; 2....

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  • ...Using the B-and R-band nucleus–galaxy decomposition of Granato et al. (1993), and assuming normal optical-to-IR (V − K = 3.22 mag; Clavel et al. 1989) and K − L colors, we estimate a total galaxy flux of 20 mJy and 17 mJy respectively at 3.5µm....

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  • ...We can estimate the distance to the central source of the innermost and hottest dust grains in Mrk 279, rin, by scaling directly from Fairall 9 (Clavel et al. 1989)....

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  • ...…time delay corresponds closely to the lighttravel time to the dust sublimation radius rin; measured values of rin are 400 light days for Fairall 9 (Clavel et al. 1989), 50 light days for NGC 1566 (Baribaud et al. 1992), 80 light days for NGC 3783 (Glass 1992) and 32 light days for Mrk 744 (Nelson…...

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Journal ArticleDOI
TL;DR: In this paper, a method for the automatic relative scaling of spectra in which one or more lines with constant flux are present is described, taking into account differences in spectral resolution, flux factors and spectral shifts.
Abstract: A method is described for the automatic relative scaling of spectra in which one or more lines with constant flux are present. The algorithm takes into account differences in spectral resolution, flux factors and spectral shifts. It was developed for the relative calibration of series of optical spectra obtained in variability studies of active galactic nuclei, but it also can be used for other purposes, e.g., the subtraction of an underlying stellar continuum in AGN with a template spectrum. Tests show that a high degree of accuracy is obtained, and that the method is superior to scaling the spectra by eye or measuring the narrow line fluxes.

141 citations

Journal ArticleDOI
TL;DR: Les observations VLA des masers H 2 O extragalactiques tres lumineux (≥100 L ) contenus dans NGC 4258 and NGC 1068 imposent des limites superieures de 1,3 and 3,5 pc respectivement a leur etendue spatiale, au centre de chaque galaxie as mentioned in this paper.
Abstract: Les observations VLA des masers H 2 O extragalactiques tres lumineux (≥100 L ○. ) contenus dans NGC 4258 et NGC 1068 imposent des limites superieures de 1,3 et 3,5 pc respectivement a leur etendue spatiale, au centre de chaque galaxie. Ils sont probablement associes a des condensations de gaz moleculaire tres denses plutot qu'a de jeunes objets stellaires

97 citations

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