The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements
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.
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Pennsylvania State University1, Drexel University2, York University3, Princeton University4, University of Washington5, University of Arizona6, University of Southampton7, Max Planck Society8, Johns Hopkins University9, Fermilab10, University of Chicago11, New Mexico State University12, New York University13, University of Tokyo14, Microsoft15, Korea Institute for Advanced Study16, Seoul National University17, National Science Foundation18, Lawrence Berkeley National Laboratory19, Ohio State University20
TL;DR: The fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar catalog as discussed by the authors contains 105,783 spectroscopically confirmed quasars, which is based upon the SDSS Seventh Data Release.
Abstract: We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than Mi = –22.0 (in a cosmology with H 0 = 70 km s–1 Mpc–1, Ω M = 0.3, and ΩΛ = 0.7), have at least one emission line with FWHM larger than 1000 km s–1 or have interesting/complex absorption features, are fainter than i 15.0, and have highly reliable redshifts. The catalog covers an area of 9380 deg2. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than 4, of which 56 are at redshifts greater than 5. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i < 19. For each object the catalog presents positions accurate to better than 01 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 A at a spectral resolution of 2000; the spectra can be retrieved from the SDSS public database using the information provided in the catalog. Over 96% of the objects in the catalog were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.
1,110 citations
Cites background from "The Radius-Luminosity Relationship ..."
...…in the catalog are less susceptible to host galaxy contamination than are fixed-aperture measurements, the nucleus of the host galaxy can still contribute appreciably to this measurement for the lowest luminosity entries in the catalog (e.g., Hao et al. 2005, Bentz et al. 2006, Croom et al. 2009)....
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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 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 background or methods or result from "The Radius-Luminosity Relationship ..."
...A preliminary study by Bentz et al. (2006a) presented two-dimensional fits to high-resolutionHST images of 14 reverberation-mapped AGNs, from which the host-galaxy contribution was determined....
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...Indeed, our decision to revisit the Bentz et al. (2006a) fits was motivated at least in part by such considerations....
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...…residuals andχ2 values from the new fits, combined with the results of the consistency checks, lead us to believe that the galaxy fits in this work more accurately describe the underlying host-galaxy surface brightness ditributions than the simplistic fits determined by Bentz et al. (2006a)....
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...However, we improve upon the results presented by Bentz et al. (2006a) in that we employed the more general Sérsic function for modeling bulges and we allow for additional parameters to describe other surface brightness components (such as a bar or inner bulge component)....
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...The triangles are the new equivalent width measurements for the same emission line fluxes, but in this case the continuum measurements have been adjusted by the hostgalaxy value from Bentz et al. (2006a)....
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TL;DR: In this article, it was shown that the accretion process is exactly the same for small and large black holes, provided that a correction is made to take account of variations in the rate of the process.
Abstract: The central engines that drive active galactic nuclei are thought to be supermassive black holes. A long-standing question in astrophysics is whether these central engines vary like Galactic black hole systems when scaled up to 'supermassive' proportions. If they do, it becomes possible to predict how active galactic nuclei should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. A new study suggests that yes, the accretion process is exactly the same for small and large black holes. Provided, that is, that a correction is made to take account of variations in the rate of the accretion process. Active galactic nuclei vary in a manner similar to Galactic black hole systems when appropriately scaled up by mass, meaning it is possible to determine how active galactic nuclei should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. A long-standing question is whether active galactic nuclei (AGN) vary like Galactic black hole systems when appropriately scaled up by mass1,2,3. If so, we can then determine how AGN should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. As X-ray emission is produced very close to the black holes, it provides one of the best diagnostics of their behaviour. A characteristic timescale—which potentially could tell us about the mass of the black hole—is found in the X-ray variations from both AGN and Galactic black holes1,2,3,4,5,6, but whether it is physically meaningful to compare the two has been questioned7. Here we report that, after correcting for variations in the accretion rate, the timescales can be physically linked, revealing that the accretion process is exactly the same for small and large black holes. Strong support for this linkage comes, perhaps surprisingly, from the permitted optical emission lines in AGN whose widths (in both broad-line AGN and narrow-emission-line Seyfert 1 galaxies) correlate strongly with the characteristic X-ray timescale, exactly as expected from the AGN black hole masses and accretion rates. So AGN really are just scaled-up Galactic black holes.
639 citations
TL;DR: In this paper, the authors presented a model that reproduces the observed virial mass distribution, quasar luminosity function, and line width distribution of their sample; it has an underlying BH mass distribution dN/dlog M ∝ M−2.
Abstract: We compile black hole (BH) masses for ~60,000 quasars in the redshift range 0.1 z 4.5 included in the Fifth Data Release of the Sloan Digital Sky Survey, using virial BH mass estimators based on the Hβ, Mg II, and C IV emission lines. Within our sample, the widths of the three lines follow lognormal distributions, with means and dispersions that do not depend strongly on luminosity or redshift. The Mg II- and Hβ-estimated BH masses are consistent with one another, but there is a positive bias between the C IV- and Mg II-estimated BH masses correlated with the C IV-Mg II blueshift, suggesting that the C IV estimator is more severely affected by a disk wind. If the underlying BH mass distribution decreases with mass and the Eddington ratio distribution at fixed true BH mass has nonzero width, we show that the measured virial BH mass and Eddington ratio distributions within finite luminosity bins are subject to Malmquist bias. We present a model that reproduces the observed virial mass distribution, quasar luminosity function, and line width distribution of our sample; it has an underlying BH mass distribution dN/dlog M ∝ M−2.6 and a lognormal true Eddington ratio distribution at fixed true mass with dispersion 0.4 dex and mean dependent on BH mass. In this model, the observed virial mass (Eddington ratio) distribution for the SDSS sample is biased high (low) by ~0.6 dex within finite luminosity bins. Finally, we compare virial BH masses of radio and broad absorption line quasars with ordinary quasars matched in redshift and luminosity.
622 citations
Cites background from "The Radius-Luminosity Relationship ..."
...Changes in these virial relations (e.g., a different slope in theR− L relation, etc., see Bentz et al. 2006; Netzer et al. 2007) will certainly change the values of our model parameters....
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...…the most recent calibrations available (McLure & Dunlop 2004; Vestergaard & Peterson 2006), it is quite likely that those calibrations will change when the updatedR− L relation and virial coefficient (zero-point offset) are incorporated (Onken et al. 2004; Bentz et al. 2006; Kaspi et al. 2007)....
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...Current reverberation mapping data indicate a scatter of∼ 0.2− 0.35 dex in luminosity at fixed BLR size (e.g., Kaspi et al. 2005; Bentz et al. 2006)....
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References
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TL;DR: In this article, a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed, is presented.
Abstract: We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected. To generate the full-sky dust maps, we must first remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 μm DIRBE map against the Leiden-Dwingeloo map of H I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 μm flux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 μm map no significant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 ± 13 nW m-2 sr-1 at 140 μm and of 17 ± 4 nW m-2 sr-1 at 240 μm (95% confidence). This integrated flux ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. To calibrate our maps, we assume a standard reddening law and use the colors of elliptical galaxies to measure the reddening per unit flux density of 100 μm emission. We find consistent calibration using the B-R color distribution of a sample of the 106 brightest cluster ellipticals, as well as a sample of 384 ellipticals with B-V and Mg line strength measurements. For the latter sample, we use the correlation of intrinsic B-V versus Mg2 index to tighten the power of the test greatly. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles reddening estimates in regions of low and moderate reddening. The maps are expected to be significantly more accurate in regions of high reddening. These dust maps will also be useful for estimating millimeter emission that contaminates cosmic microwave background radiation experiments and for estimating soft X-ray absorption. We describe how to access our maps readily for general use.
15,988 citations
"The Radius-Luminosity Relationship ..." refers methods in this paper
...Following Kaspi et al. (2005), we corrected for galactic absorption using the Schlegel et al. (1998) E(B − V ) values listed in the NASA/IPAC Extragalactic Database (NED) and the extinction curve of Cardelli et al. (1989), adjusted to AV /E(B − V ) = 3.1....
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TL;DR: In this paper, the authors presented a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed.
Abstract: We present a full sky 100 micron map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 micron and 240 micron data, we have constructed a map of the dust temperature, so that the 100 micron map can be converted to a map proportional to dust column density. The result of these manipulations is a map with DIRBE-quality calibration and IRAS resolution.
To generate the full sky dust maps, we must first remove zodiacal light contamination as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 micron DIRBE map against the Leiden- Dwingeloo map of H_I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 micron flux. For the 100 micron map, no significant CIB is detected. In the 140 micron and 240 micron maps, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 \pm 13 nW/m^2/sr at 140 micron, and 17 \pm 4 nW/m^2/sr at 240 micron (95% confidence). This integrated flux is ~2 times that extrapolated from optical galaxies in the Hubble Deep Field.
The primary use of these maps is likely to be as a new estimator of Galactic extinction. We demonstrate that the new maps are twice as accurate as the older Burstein-Heiles estimates in regions of low and moderate reddening. These dust maps will also be useful for estimating millimeter emission that contaminates CMBR experiments and for estimating soft X-ray absorption.
14,295 citations
TL;DR: In this article, the average extinction law over the 3.5 micron to 0.125 wavelength range was derived for both diffuse and dense regions of the interstellar medium. And the validity of the law over a large wavelength interval suggests that the processes which modify the sizes and compositions of grains are stochastic in nature.
Abstract: The parameterized extinction data of Fitzpatrick and Massa (1986, 1988) for the ultraviolet and various sources for the optical and near-infrared are used to derive a meaningful average extinction law over the 3.5 micron to 0.125 wavelength range which is applicable to both diffuse and dense regions of the interstellar medium. The law depends on only one parameter R(V) = A(V)/E(B-V). An analytic formula is given for the mean extinction law which can be used to calculate color excesses or to deredden observations. The validity of the law over a large wavelength interval suggests that the processes which modify the sizes and compositions of grains are stochastic in nature and very efficient.
11,704 citations
"The Radius-Luminosity Relationship ..." refers methods in this paper
...Following Kaspi et al. (2005), we corrected for galactic absorption using the Schlegel et al. (1998) E(B − V ) values listed in the NASA/IPAC Extragalactic Database (NED) and the extinction curve of Cardelli et al. (1989), adjusted to AV /E(B − V ) = 3.1....
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01 Jan 1989
TL;DR: This paper presents a list of recommended recipes for making CDRom decks and some examples of how these recipes can be modified to suit theommelier's needs.
Abstract: Keywords: informatique ; numerical recipes Note: contient un CDRom Reference Record created on 2004-09-07, modified on 2016-08-08
4,920 citations
"The Radius-Luminosity Relationship ..." refers background in this paper
...The generalized least-squares method of Jefferys (1980, 1981) implemented by GaussFit has the virtue of directly addressing the explicit nonlinearity of the problem of fitting lines through data with errors in both variables, whereas BCES and FITEXY use iterative linear approximations to estimate the best-fit parameters....
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...FITEXY (Press et al. 1992), which estimates the parameters of a straight-line fit through the data including errors in both coordinates....
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...FITEXY numerically solves for the minimum orthogonal χ2 using an interative root-finding algorithm....
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