skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI

Abstract

We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ∼40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ∼0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlightsmore » the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ∼0.13 dex.« less

Authors:
;  [1]; ;  [2];  [3]
  1. Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark)
  2. Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
  3. Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States)
Publication Date:
OSTI Identifier:
22522060
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 801; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; COLOR; COMPUTERIZED SIMULATION; DISTANCE; GALAXIES; GALAXY NUCLEI; LUMINOSITY; MASS; MONTE CARLO METHOD; NONLINEAR PROBLEMS; VARIATIONS

Citation Formats

Kilerci Eser, E., Vestergaard, M., Peterson, B. M., Denney, K. D., and Bentz, M. C., E-mail: ecekilerci@dark-cosmology.dk, E-mail: vester@dark-cosmology.dk, E-mail: kelly@astronomy.ohio-state.edu, E-mail: peterson@astronomy.ohio-state.edu, E-mail: bentz@chara.gsu.edu. ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI. United States: N. p., 2015. Web. doi:10.1088/0004-637X/801/1/8.
Kilerci Eser, E., Vestergaard, M., Peterson, B. M., Denney, K. D., & Bentz, M. C., E-mail: ecekilerci@dark-cosmology.dk, E-mail: vester@dark-cosmology.dk, E-mail: kelly@astronomy.ohio-state.edu, E-mail: peterson@astronomy.ohio-state.edu, E-mail: bentz@chara.gsu.edu. ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI. United States. doi:10.1088/0004-637X/801/1/8.
Kilerci Eser, E., Vestergaard, M., Peterson, B. M., Denney, K. D., and Bentz, M. C., E-mail: ecekilerci@dark-cosmology.dk, E-mail: vester@dark-cosmology.dk, E-mail: kelly@astronomy.ohio-state.edu, E-mail: peterson@astronomy.ohio-state.edu, E-mail: bentz@chara.gsu.edu. 2015. "ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI". United States. doi:10.1088/0004-637X/801/1/8.
@article{osti_22522060,
title = {ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI},
author = {Kilerci Eser, E. and Vestergaard, M. and Peterson, B. M. and Denney, K. D. and Bentz, M. C., E-mail: ecekilerci@dark-cosmology.dk, E-mail: vester@dark-cosmology.dk, E-mail: kelly@astronomy.ohio-state.edu, E-mail: peterson@astronomy.ohio-state.edu, E-mail: bentz@chara.gsu.edu},
abstractNote = {We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ∼40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ∼0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ∼0.13 dex.},
doi = {10.1088/0004-637X/801/1/8},
journal = {Astrophysical Journal},
number = 1,
volume = 801,
place = {United States},
year = 2015,
month = 3
}
  • 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 H{beta} R {sub 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 stillmore » 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 {sub BLR}-L relationship.« less
  • 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 yieldmore » 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 0.19 {+-} 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
  • Broad-line region (BLR) sizes derived from spectral variability and BLR line widths are used to directly derive the mass (M) of the central objects of ten active galactic nuclei (AGNs) in a uniform manner. It is shown that the luminosity-weighted C IV 1549-emitting BLR radius (R) correlates with the bolometric luminosity L(Bol) and is consistent with R about sq rt L(Bol). The measurements also permit a verification of the Dibai mass-luminosity (M-L) relationship (previously derived indirectly). It is found that L(Bol) is proportional to M exp (1.1 + or - 0.3). It is found that the efficiency factor epsilon, definedmore » as the ratio of L(Bol) to the Eddington luminosity increases from 0.03 in the low-luminosity Seyferts up to 0.06 in the most luminous objects in the sample. 19 refs.« less
  • The correlation between the kinetic power P {sub jet} and intrinsic bolometric luminosity L {sub jet} of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al., we re-investigate this correlation with additional sources of black hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with P {sub jet} and L {sub jet} being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion jet scenario. Compared to previous works,more » the range of luminosity is now enlarged to more than 20 decades, i.e., from ∼10{sup 31} erg s{sup –1} to ∼10{sup 52} erg s{sup –1}, which allows for better constraining of the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same P {sub jet}-L {sub jet} correlation that was obtained from blazars and gamma-ray bursts. The slope indices we derived are 1.03 ± 0.01 for the whole sample, 0.85 ± 0.06 for the BXB subsample, 0.71 ± 0.11 for the LLAGN subsample, and 1.01 ± 0.05 for the LLAGN-blazar subsample, respectively. The correlation index around unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.« less
  • The optical luminosity function derived from quasars with M(B) less than -23 is extended to include the nuclear luminosities of Seyfert 1 galaxies. The model is fitted to the (total) luminosity data for active galaxies from a complete flux-limited survey. A good fit is obtained with dN/dL varying inversely as L exp -1.2, matching onto the steeper quasar luminosity function near M(B) = -22. Using a luminosity evolution model derived from quasar data, this feature compares well with the results from faint quasar surveys. 26 references.