Jong-Hak Woo

Active Galactic Nucleus Black Hole Masses and Bolometric Luminosities

Black hole mass, along with mass accretion rate, is a fundamental property of active galactic nuclei (AGNs). Black hole mass sets an approximate upper limit to AGN energetics via the Eddington limit. We collect and compare all AGN black hole mass estimates from the literature; these 177 masses are mostly based on the virial assumption for the broad emission lines, with the broad-line region size determined from either reverberation mapping or optical luminosity. We introduce 200 additional black hole mass estimates based on properties of the host galaxy bulges, using either the observed stellar velocity dispersion or the fundamental plane relation to infer σ; these methods assume that AGN hosts are normal galaxies. We compare 36 cases for which black hole mass has been generated by different methods and find, for individual objects, a scatter as high as a couple of orders of magnitude. The less direct the method, the larger the discrepancy with other estimates, probably due to the large scatter in the underlying correlations assumed. Using published fluxes, we calculate bolometric luminosities for 234 AGNs and investigate the relation between black hole mass and luminosity. In contrast to other studies, we find no significant correlation of black hole mass with luminosity, other than those induced by circular reasoning in the estimation of black hole mass. The Eddington limit defines an approximate upper envelope to the distribution of luminosities, but the lower envelope depends entirely on the sample of AGNs included. For any given black hole mass, there is a range in Eddington ratio of up to 3 orders of magnitude.

Black Hole Masses and Host Galaxy Evolution of Radio-Loud Active Galactic Nuclei

We report stellar velocity dispersion measurements for a sample of 28 active galactic nucleus (AGN) host galaxies, including our previous work. Using the mass-dispersion (M•-σ) and the fundamental plane relations, we estimate the black hole mass for a sample of 66 BL Lac objects and investigate the role of black hole mass in the energetics of BL Lac objects. The black hole mass range for different BL Lac spectral types is similar, 107 < M• < 4 × 109. Neither X-ray nor radio luminosity correlates with black hole mass. Low-frequency-peaked BL Lac objects have higher Eddington ratios on average, because of either more beaming or higher intrinsic power. For the black hole mass range 3 × 107 < M• < 109, the radio luminosity of BL Lac objects and flat-spectrum radio quasars spans over 4 orders of magnitude, with BL Lac objects being low-power AGNs. We also investigate the evolution of host galaxies for 39 AGNs out to z ≈ 0.5 with measured stellar velocity dispersions. Comparing the mass-to-light ratio evolution in the observed frame with population synthesis models, we find that single-burst star formation models with zform = 1.4 are consistent with the observations. From our zform = 1.4 model, we estimated the intrinsic mass-to-light ratio evolution in the Cousins R band, Δ log(M/L)/Δz = -0.502 ± 0.08, consistent with that of normal early-type galaxies.

The Independence of Active Galactic Nucleus Black Hole Mass and Radio Loudness

We revisit the issue of whether radio loudness in AGN is associated with central black hole mass, as has been suggested in the literature. We present new estimates of black hole mass for 295 AGN (mostly radio-quiet), calculating their radio loudnesses from published radio and optical fluxes, and combine with our previously published values, for a sample of 452 AGN for which both black hole mass and radio loudness (or upper limits thereto) are known. Among the radio-quiet AGN, there are now many black holes with mass larger than 10 M⊙, extending to the same high black hole masses as radio-loud AGN of the same redshifts. Over the full sample, the black hole masses of radio-loud and radioquiet AGN span the same large range, 10 − 1010M⊙. We conclude that radio loudness in AGN does not depend strongly on central black hole mass. Subject headings: galaxies: active quasars: general

Cosmic Evolution of Black Holes And Spheroids. 1, the M(BH)-Sigma Relation at Z=0.36

We test the evolution of the correlation between black hole mass and bulge velocity dispersion (M{sub BH} - {sigma}), using a carefully selected sample of 14 Seyfert 1 galaxies at z = 0.36 {+-} 0.01. We measure velocity dispersion from stellar absorption lines around Mgb (5175 {angstrom}) and Fe (5270 {angstrom}) using high S/N Keck spectra, and estimate black hole mass from the H{beta} line width and the optical luminosity at 5100 {angstrom}, based on the empirically calibrated photo-ionization method. We find a significant offset from the local relation, in the sense that velocity dispersions were smaller for given black hole masses at z = 0.36 than locally. We investigate various sources of systematic uncertainties and find that those cannot account for the observed offset. The measured offset is {Delta} log M{sub BH} = 0.62 {+-} 0.10 {+-} 0.25, i.e. {Delta} log {sigma} = 0.15 {+-} 0.03 {+-} 0.06, where the error bars include a random component and an upper limit to the systematics. At face value, this result implies a substantial growth of bulges in the last 4 Gyr, assuming that the local M{sub BH} - {sigma} relation is the universal evolutionary end-point. Along with two samples of activemorexa0» galaxies with consistently determined black hole mass and stellar velocity dispersion taken from the literature, we quantify the observed evolution with the best fit linear relation, {Delta} log M{sub BH} = (1.66 {+-} 0.43)z + (0.04 {+-} 0.09) with respect to the local relationship of Tremaine et al. (2002), and {Delta} log M{sub BH} = (1.55 {+-} 0.46)z +(0.01 {+-} 0.12) with respect to that of Ferrarese (2002). This result is consistent with the growth of black holes predating the final growth of bulges at these mass scales ( = 170 km s{sup -1}).«xa0less

The Independence of AGN black hole mass and radio - loudness

We revisit the issue of whether radio loudness in AGN is associated with central black hole mass, as has been suggested in the literature. We present new estimates of black hole mass for 295 AGN (mostly radio-quiet), calculating their radio loudnesses from published radio and optical fluxes, and combine with our previously published values, for a sample of 452 AGN for which both black hole mass and radio loudness (or upper limits thereto) are known. Among the radio-quiet AGN, there are now many black holes with mass larger than 10 M⊙, extending to the same high black hole masses as radio-loud AGN of the same redshifts. Over the full sample, the black hole masses of radio-loud and radioquiet AGN span the same large range, 10 − 1010M⊙. We conclude that radio loudness in AGN does not depend strongly on central black hole mass. Subject headings: galaxies: active quasars: general

Testing Intermediate-Age Stellar Evolution Models with VLT Photometry of Large Magellanic Cloud Clusters. I. The Data*

This is the first of a series of three papers devoted to the calibration of a few parameters of crucial importance in the modeling of the evolution of intermediate-mass stars, with special attention to the amount of convective core overshoot. To this end we acquired deep V and R photometry for three globular clusters of the Large Magellanic Cloud (LMC), namely NGC 2173, SL 556 and NGC 2155, in the age interval 1-3 Gyr. In this first paper, we describe the aim of the project, the VLT observations and data reduction, and we make preliminary comparisons of the color-magnitude diagrams with both Padova and Yonsei-Yale isochrones. Two following papers in this series present the results of a detailed analysis of these data, independently carried out by members of the Yale and Padova stellar evolution groups. This allows us to compare both sets of models and discuss their main differences, as well as the systematic effects that they would have to the determination of the ages and metallicities of intermediate-age single stellar populations.

Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. I. The data

This is the first of a series of three papers devoted to the calibration of a few parameters of crucial importance in the modeling of the evolution of intermediate-mass stars, with special attention to the amount of convective core overshoot. To this end we acquired deep V and R photometry for three globular clusters of the Large Magellanic Cloud (LMC), namely NGC 2173, SL 556 and NGC 2155, in the age interval 1-3 Gyr. In this first paper, we describe the aim of the project, the VLT observations and data reduction, and we make preliminary comparisons of the color-magnitude diagrams with both Padova and Yonsei-Yale isochrones. Two following papers in this series present the results of a detailed analysis of these data, independently carried out by members of the Yale and Padova stellar evolution groups. This allows us to compare both sets of models and discuss their main differences, as well as the systematic effects that they would have to the determination of the ages and metallicities of intermediate-age single stellar populations.

The Fundamental Plane Evolution of Active Galactic Nucleus Host Galaxies

We measured the stellar velocity dispersions of 15 active galactic nucleus (AGN) host galaxies at redshifts as high as ~0.34. Combining these with published velocity dispersion measurements from the literature, we study the fundamental plane of AGN host galaxies and its evolution. BL Lac object hosts and radio galaxies seem to lie on the same fundamental plane as normal early-type galaxies. The evolution of the mass-to-light ratio of AGN host galaxies shows a similar trend to that observed in normal early-type galaxies, consistent with single-burst passive evolution models with formation redshifts z 1. The lack of a significant difference between normal and AGN host galaxies in the fundamental plane supports the grand unification picture wherein AGNs are a transient phase in the evolution of normal galaxies. The black hole masses of BL Lac objects and radio galaxies, derived using the mass dispersion relation, are similar. The black hole mass is independent of BL Lac object type. The local black hole mass-host galaxy luminosity relation of our subsample at z < 0.1 is similar to that of local normal and radio galaxies, but is less well defined at higher redshift owing to the luminosity evolution of the host galaxies.

Testing Intermediate-Age Stellar Evolution Models with VLT Photometry of Large Magellanic Cloud Clusters. II. Analysis with the Yale Models*

Using Yale stellar evolution models, we present an analysis of the color-magnitude diagrams (CMDs) of three intermediate-age LMC clusters, namely, NGC 2173, SL 556, and NGC 2155, obtained with the Very Large Telescope. The main goal of our project is to investigate the amount of convective core overshoot necessary to reproduce the CMDs of relatively metal-poor, intermediate-age stellar populations, to check whether the extrapolation that is usually made from solar metallicity is valid. In the process, we obtained values for the binary fraction of each cluster, together with refined age estimates. Our method involved the comparison of the observed CMDs with synthetic CMDs computed using various values of the overshoot parameter and binary fraction. We conclude that a moderate amount of overshoot and some fraction of binary stars are essential for reproducing the observed shapes around the turnoff in the CMDs of all three clusters: unresolved binary stars fill in the expected core contraction gap and make a unique sequence near the gap, which cannot be reproduced by single stars alone, even with a larger amount of overshoot. We utilize ratios of the number of stars in different areas around the core contraction gap to constrain the binary fraction, which is around 10%–20% (for primary-to-secondary mass ratio ≥0.7) in all three clusters. Even if binary stars contaminate the core contraction gap, it is shown that the overshoot parameter can be inferred from the color dispersion of the stars around the contraction gap, regardless of the assumed binary fraction. From our overall analysis such as shape of isochrones, star counts, color distribution, and synthetic CMD comparisons, we conclude that overshoot ~20% of the local pressure scale height best reproduces the CMD properties of all three clusters. The best age estimates are 1.5, 2.1, and 2.9 Gyr for NGC 2173, SL 556, and NGC 2155, respectively.

Empirical Constraints on Convective Core Overshoot

In stellar evolution calculations, the local pressure scale height is often used to empirically constrain the amount of convective core overshoot. However, this method brings unsatisfactory results for low- mass stars (1.1¨1.2 for which have very small cores or no convective core at all. Follow- M _ Z Z _ ), ing Roxburghs integral constraint, we implemented an upper limit of overshoot within the conventional method of a parameterization to remove an overly large overshoot eUect on low-mass stars. The erron- eously large eUect of core overshoot due to the failure of a parameterization can be eUectively corrected by limiting the amount of overshoot to 15% of the core radius; 15% of the core radius would be a proper limit of overshoot, which can be implemented in a stellar evolution code for intermediate- to low-mass stars. The temperature structure of the overshoot region does not play a crucial role in stellar evolution since this transition region is very thin.