Daeseong Park

Modelling reverberation mapping data - II. Dynamical modelling of the Lick AGN Monitoring Project 2008 data set

Author(s): Pancoast, A; Brewer, BJ; Treu, T; Park, D; Barth, AJ; Bentz, MC; Woo, JH | Abstract:

RECALIBRATION OF THE VIRIAL FACTOR AND M BH-σ* RELATION FOR LOCAL ACTIVE GALAXIES

Determining the virial factor of the broad-line region gas is crucial for calibrating active galactic nucleus black hole mass estimators, since the measured line-of-sight velocity needs to be converted into the intrinsic virial velocity. The average virial factor has been empirically calibrated based on the M BH-σ* relation of quiescent galaxies, but the claimed values differ by a factor of two in recent studies. We investigate the origin of the difference by measuring the M BH-σ* relation using an updated galaxy sample from the literature and explore the dependence of the virial factor on various fitting methods. We find that the discrepancy is primarily caused by the sample selection, while the difference stemming from the various regression methods is marginal. However, we generally prefer the FITEXY and Bayesian estimators based on Monte Carlo simulations for the M BH-σ* relation. In addition, the choice of independent variable in the regression leads to ~0.2 dex variation in the virial factor inferred from the calibration process. Based on the determined virial factor, we present the updated M BH-σ* relation of local active galaxies.

Do Quiescent and Active Galaxies Have Different M_(BH)-σ* Relations?

To investigate the validity of the assumption that quiescent galaxies and active galaxies follow the same black hole mass (M_BH)-stellar velocity dispersion (σ*) relation, as required for the calibration of M_BH estimators for broad line active galactic nuclei (AGNs), we determine and compare the M_BH-σ* relations, respectively, for quiescent and active galaxies. For the quiescent galaxy sample, composed of 72 dynamical M_BH measurements, we update σ* for 28 galaxies using homogeneous H-band measurements that are corrected for galaxy rotation. For active galaxies, we collect 25 reverberation-mapped AGNs and improve σ* measurement for two objects. Combining the two samples, we determine the virial factor f, first by scaling the active galaxy sample to the M_BH-σ* relation of quiescent galaxies, and second by simultaneously fitting the quiescent and active galaxy samples, as f=5.1^(+1.5)_(-1.1) and f=5.9^(+2.1)_(-1.5), respectively. The M_BH-σ* relation of active galaxies appears to be shallower than that of quiescent galaxies. However, the discrepancy is caused by a difference in the accessible M_BH distribution at given σ*, primarily due to the difficulty of measuring reliable stellar velocity dispersion for the host galaxies of luminous AGNs. Accounting for the selection effects, we find that active and quiescent galaxies are consistent with following intrinsically the same M_BH-σ* relation.

The Black Hole Mass–Stellar Velocity Dispersion Relation of Narrow-line Seyfert 1 Galaxies

Narrow-line Seyfert 1 galaxies (NLS1s) are arguably one of the key active galactic nucleus (AGN) subclasses in investigating the origin of the black hole mass–stellar velocity dispersion () relation because of their high accretion rate and significantly low . Currently, it is under discussion whether present-day NLS1s offset from the relation. Using the directly measured stellar velocity dispersion of 93 NLS1s at z < 0.1, and estimates based on the updated mass estimators, we investigate the relation of NLS1s in comparison with broad-line AGNs. We find no strong evidence that the NLS1s deviates from the relation, which is defined by reverberation-mapped type 1 AGNs and quiescent galaxies. However, there is a clear trend of the offset with the host galaxy morphology, i.e., galaxies that are more inclined toward the LOS have higher stellar velocity dispersions, suggesting that the rotational broadening plays a role in measuring stellar velocity dispersion based on the single-aperture spectra from the Sloan Digital Sky Survey. In addition, we provide the virial factor (f = 1.12), for estimators based on the FWHM of Hβ, by jointly fitting the relation using quiescent galaxies and reverberation-mapped AGNs.

CALIBRATING C-IV-BASED BLACK HOLE MASS ESTIMATORS

We present the single-epoch black hole mass estimators based on the C IV λ1549 broad emission line, using the updated sample of the reverberation-mapped active galactic nuclei and high-quality UV spectra. By performing multi-component spectral fitting analysis, we measure the C IV line widths (FWHMC IV and line dispersion, σC IV ) and the continuum luminosity at 1350 A (L 1350) to calibrate the C-IV-based mass estimators. By comparing with the Hβ reverberation-based masses, we provide new mass estimators with the best-fit relationships, i.e., and . The new C-IV-based mass estimators show significant mass-dependent systematic difference compared to the estimators commonly used in the literature. Using the published Sloan Digital Sky Survey QSO catalog, we show that the black hole mass of high-redshift QSOs decreases on average by ~0.25 dex if our recipe is adopted.

Void ellipticity distribution as a probe of cosmology.

Cosmic voids refer to the large empty regions in the Universe with a very low number density of galaxies. Voids are likely to be severely disturbed by the tidal effect from the surrounding dark matter. We derive a completely analytic model for the void ellipticity distribution from physical principles. We use the spatial distribution of galaxies in a void as a measure of its shape, tracking the trajectory of the void galaxies under the influence of the tidal field using Lagrangian perturbation theory. Our model implies that the void ellipticity distribution depends sensitively on the cosmological parameters. Testing our model against the high-resolution Millennium Run simulation, we find excellent quantitative agreements of the analytic predictions with the numerical results.

CONSTRAINING THE DARK ENERGY EQUATION OF STATE WITH COSMIC VOIDS

Our universe is observed to be accelerating due to the dominant dark energy with negative pressure. The dark energy equation of state (w) holds a key to understanding the ultimate fate of the universe. The cosmic voids behave like bubbles in the universe so that its shapes must be quite sensitive to the background cosmology. Assuming a flat universe and using the priors on the matter density parameter (Ω m ) and the dimensionless Hubble parameter (h), we demonstrate analytically that the ellipticity evolution of cosmic voids may be a sensitive probe of the dark energy equation of state. We also discuss the parameter degeneracy between w and Ω m .

Rotation of cosmic voids and void spin statistics

We present a theoretical study of void spins and their correlation properties. The concept of the spin angular momentum for an unbound void is introduced to quantify the effect of the tidal field on the distribution of matter that makes up the void. Both the analytical and numerical approaches are used for our study. Analytically, we adopt the linear tidal-torque model to evaluate the void spin-spin and spin-density correlations, assuming that a void forms in the initial region where the inertia momentum and the tidal shear tensors are maximally uncorrelated with each other. Numerically, we use the Millennium Run galaxy catalog to find voids and calculate their spin statistics. The numerical results turn out to be in excellent agreement with the analytic predictions, both of which consistently show that there are strong spatial alignments between the spin axes of neighboring voids and strong antialignments between the void spin axes and the directions to the nearest voids. We expect that our work will provide a deeper insight into the origin and properties of voids and the large-scale structure.

Cosmic evolution of black holes and spheroids. V. The relation between Black Hole Mass and Host Galaxy Luminosity for a sample of 79 active galaxies

We investigate the cosmic evolution of the black hole (BH) mass -- bulge luminosity relation using a sample of 52 active galaxies at

A sub-kpc-scale binary active galactic nucleus with double narrow-line regions

z \sim 0.36