119542129
Black hole mass and accretion rate of active galactic nuclei
The determination of the central black hole mass is crucial to the understanding of AGN physics. In this paper we briefly review some methods that are currently used to estimate the black hole mass of AGNs. Particularly we demonstrate the importance of two correlations: one between the black hole mass and the stellar velocity dispersion and another one between the broad line region (BLR) size and the optical continuum luminosity. Besides applying these relations in deriving black hole masses of various types of AGNs, we also employed the fundamental plane of elliptical galaxies to estimate the central velocity dispersions of AGN host galaxies, and then the black hole masses of AGNs including BL Lac objects. In addition, we derived another empirical relation between the BLR size and H_beta emission line luminosity from AGNs with the BLR size measured by reverberation mapping studies, and argued that more accurate black hole masses of extremely radio-loud AGNs could be obtained with it than using the usual R-L_{5100\AA} relation because of the jet contribution to the optical continuum. Finally we pointed out that black hole mass estimation is very much helpful to determine the accretion rate and understand the accretion process in AGNs.
2227030
Testing the transition layer model of quasi-periodic oscillations in neutron star X-ray binaries
We compare the theoretical predictions of the transition layer model with some observational features of quasi-periodic oscillations (QPOs) in neutron star X-ray binaries. We found that the correlation between horizontal branch oscillation (HBO) frequencies and kilohertz (kHz) QPO frequencies, the difference between the low-frequency QPOs in atoll sources and HBOs in Z sources, and the correlation between the frequencies of low-frequency QPOs and break frequencies can be well explained by the transition layer model, provided the neutron star mass is around 1.4 M☉ and the angle between magnetosphere equator and accretion disk plane is around 6°. The observed decrease of peak separation between the two kHz QPO frequencies with the increase of the kHz QPO frequencies and the increase of QPO frequencies with the increase of inferred mass accretion rate are also consistent with the theoretical predictions of the transition layer model. In addition, we derive a simple equation that can be adopted to estimate the angle (δ) between magnetosphere equator and accretion disk plane by use of the simultaneously observed QPO frequency data. We estimate this angle, in the range of 4°-8°, for five Z sources and two atoll sources. The nearly constant δ value for each source, derived from the different sets of simultaneously observed QPO frequency data, provides a strong test of the theoretical model. Finally, we suggest that similar transition layer oscillations may be responsible for the observed QPOs in accretion-powered millisecond X-ray pulsars and Galactic black hole candidates.
2132712
Inclinations and black hole masses of Seyfert 1 galaxies
A tight correlation between black hole mass (MBH) and central velocity dispersion (σ) has been found recently for both active and quiescent galaxies. By applying this correlation, we develop a simple method to derive the inclination angles for a sample of 11 Seyfert 1 galaxies that have both measured central velocity dispersions and black hole masses estimated by reverberation mapping. These angles, with a mean value of 36° that agrees well with the result obtained by fitting the iron Kα lines of Seyfert 1 galaxies observed with ASCA, provide further support to the orientation-dependent unification scheme of active galactic nuclei (AGNs). A positive correlation of the inclinations with observed FWHMs of the Hβ line and a possible anticorrelation with the nuclear radio loudness have been found. We conclude that more accurate knowledge of inclinations and broad-line region dynamics is needed to improve the black hole mass determination of AGNs with the reverberation mapping technique.
2377462
Galaxy bulge formation: Interplay with dark matter halo and central supermassive black hole
We present a simple scenario where the formation of galactic bulges was regulated by the dark halo gravity and regulates the growth of the central supermassive black hole. Assuming the angular momentum is low, we suggest that bulges form in a runaway collapse due to the "gravothermal" instability once the central gas density or pressure exceeds a certain threshold. We emphasize that the threshold is nearly universal, set by the background NFW dark matter gravity gDM ~ 1.2 × 10-8 cm s-2 in the central cusps of halos. Unlike known thresholds for gradual formation of galaxy disks, we show that the universal "halo-regulated" star formation threshold for spheroids matches the very high star formation rate and star formation efficiency seen in high-redshift observations of central starburst regions. The starburst feedback also builds up a pressure shortly after the collapse. This large pressure could act both outward to halt further infall of gas from larger scales and inward to counter the Compton-thick wind launched from the central black hole in an Eddington accretion. Assuming the feedback balances inward and outward forces, our scenario naturally gives rise to the black hole-bulge relationships observed in the local universe.
118357880
ON THE STRUCTURE OF ACCRETION DISKS WITH OUTFLOWS
To study the outflows from accretion disks, we solve the set of hydrodynamic equations for accretion disks in spherical coordinates (rθ) to obtain the explicit structure along the θ-direction. Using self-similar assumptions in the radial direction, we change the equations to a set of ordinary differential equations about the θ-coordinate, which are then solved with symmetrical boundary conditions in the equatorial plane; the velocity field is then obtained. The α viscosity prescription is applied and an advective factor f is used to simplify the energy equation. The results display thinner, quasi-Keplerian disks for Shakura-Sunyaev disks; thicker, sub-Keplerian disks for advection-dominated accretion flows; and slim disks which are consistent with previous popular analytical models. However, an inflow region and an outflow region always exist, except when the viscosity parameter α is too large, which supports the results of some recent numerical simulation works. Our results indicate that the outflows should be common in various accretion disks and may be stronger in slim disks, where both advection and radiation pressure are dominant. We also present the structure's dependence on the input parameters and discuss their physical meanings. The caveats of this work and possible improvements for the future are discussed.
199676816
Discovering the missing bright quasars at intermediate redshifts based on the optical/near-IR color selections
197508077
Twist-3 Distribution Amplitudes of Scalar Mesons within the QCD Sum Rules and Its Application to the $B \to S$ Transition Form Factors
We investigate the twist-3 light cone distribution amplitudes (LCDAs) of the scalar mesons $a_0$, $K^{\ast}_0$ and $f_0$ within the QCD sum rules. The sum rules are improved by a consistent treatment of the sizable mass effects. Adopting the valence quark component $(\bar{q}_1 q_2)$ as the dominant structure of the scalar mesons, our estimation for their masses are close to the measured $a_0(1450)$, $K^{\ast}_0(1430)$ and $f_0(1710)$. From the sum rules, we obtain the first two non-zero moments of the twist-3 DAs $\phi^{s,\sigma}_{a_0}$: $ =0.369 (0.245)$ and $ =0.203 (0.093)$; those of the twist-3 DAs $\phi_{K^*_0}^{s,\sigma}$: $ =0.004 (0.355)$ and $ =0.018 (0.207)$; and those of the twist-3 DAs $\phi_{f_0}^{s,\sigma}$: $ =0.335 (0.212)$ and $ =0.196 (0.088)$, respectively. As an application of these twist-3 LCDAs, we study the $B \to S$ transition form factors by introducing proper chiral currents in the correlator, which is constructed such that the twist-3 DAs give dominant contribution and the twist-2 DAs make negligible contribution. Our results of the $B \to S$ form factors at the large recoil region $q^2 \simeq 0$ are consistent with those obtained in the literature.
118668401
Determination of the pion distribution amplitude
Currently, not enough is known to determine the hadron distribution amplitudes (DAs)-which are universal physical quantities in the high-energy processes involving hadrons-in order to apply perturbative QCD to exclusive processes. Even for the simplest pion, one cannot discriminate between different DA models. Conversely, one expects that processes involving pions can in principle provide strong constraints on the pion DA. For example, the pion-photon transition form factor (TFF) can get accurate information about the pion wave function or DA due to the single pion in this process. However, the data from Belle and BABAR show a big difference regarding this TFF in high-Q(2) regions; at present, they are unable to determine the pion DA. In the present paper, we think it is still possible to determine the pion DA as long as we perform a combined analysis of the existing data of the processes involving pions, such as pi -> mu(nu) over bar, pi(0) -> gamma gamma, B -> pi l nu, D -> pi l nu, etc. Based on the revised light-cone harmonic oscillator model, a convenient DA model is suggested, whose parameter B-which dominates its longitudinal behavior for phi(pi)(x, mu(2))-can be determined in a definite range by these processes. A light-cone sum rule analysis of the semileptonic processes B -> pi l nu and D -> pi l nu leads to a narrow region B = [0.01; 0.14], which indicates a slight deviation from the asymptotic DA. Then, one can predict the behavior of the pion-photon TFF in high-Q(2) regions which can be tested in future experiments. This method provides the possibility that the pion DA will be finally determined by a global fit.
54195518
Twist-3 distribution amplitudes of the pion and kaon from the QCD sum rules
Abstract.Twist-3 distribution amplitudes of the pion and kaon are studied in this paper. We calculate the first several moments for the twist-3 distribution amplitudes ($ \phi_{p,\sigma}^\pi$ and $ \phi_{p,\sigma}^K$) of the pion and kaon by applying the QCD sum rules. Our results show that (i) the first three moments of $ \phi_p^K $ and the first two moments of $ \phi_p^\pi $ and $ \phi_\sigma^{\pi,K} $ of the pion and kaon can be obtained with 30$\%$ uncertainty; (ii) the fourth moment of the $ \phi_p^\pi $ and the second moment of the $ \phi_\sigma^K $ can be obtained when the uncertainty are relaxed to 35$\%$; (iii) the fourth moment of the $ \phi_\sigma^\pi $ can be obtained only when the uncertainty are relaxed to 40$\%$; (iv) we have $m_{0\pi}^p = 1.10\pm 0.08 {\mathrm {GeV}}$ and $m_{0K}^p = 1.25\pm 0.15 {\mathrm {GeV}}$ after including the $\alpha_{\mathrm {s}}$-corrections to the perturbative part. These moments will be helpful for constructing the twist-3 wave functions of the pion and kaon.
118599552
Some mass relations for mesons and baryons in Regge phenomenology
In the quasilinear Regge trajectory ansatz, some useful linear mass inequalities, quadratic mass inequalities, and quadratic mass equalities are derived for mesons and baryons. Based on these relations, mass ranges of some mesons and baryons are given. The masses of bc and ss belonging to the pseudoscalar, vector, and tensor meson multiplets are also extracted. The J{sup P} of the baryon {xi}{sub cc}{sup +}(3520) is assigned to be (1/2){sup +}. The parameters of the (1/2){sup +} and (3/2){sup +} SU(4) baryon trajectories are extracted and the masses of the orbital excited baryons lying on the (1/2){sup +} and (3/2){sup +} trajectories are estimated. The J{sup P} assignments of baryons {xi}{sub c}(2980), {xi}{sub c}(3055), {xi}{sub c}(3077), and {xi}{sub c}(3123) are discussed. The predictions are in reasonable agreement with the existing experimental data and those suggested in many other different approaches. The mass relations and the predictions may be useful for the discovery of the unobserved meson and baryon states and the J{sup P} assignment of these states.
119278847
Information on the Pion Distribution Amplitude from the Pion-Photon Transition Form Factor with the Belle and BaBar Data
The pion-photon transition form factor (TFF) provides strong constraints on the pion distribution amplitude (DA). We perform an analysis of all existing data (CELLO, CLEO, BaBar, Belle) on the pion-photon TFF by means of light-cone pQCD approach in which we include the next-to-leading order correction to the valence-quark contribution and estimate the non-valence-quark contribution by a phenomenological model based on the TFF's limiting behavior at both $Q^2\to 0$ and $Q^2\to\infty$. At present, the pion DA is not definitely determined, it is helpful to have a pion DA model that can mimic all the suggested behaviors, especially to agree with the constraints from the pion-photon TFF in whole measured region within a consistent way. For the purpose, we adopt the conventional model for pion wavefunction/DA that has been constructed in our previous paper \cite{hw1}, whose broadness is controlled by a parameter $B$. We fix the DA parameters by using the CELLO, CLEO, BABAR and Belle data within the smaller $Q^2$ region ($Q^2 \leq 15$ GeV$^2$), where all the data are consistent with each other. And then the pion-photon TFF is extrapolated into larger $Q^2$ region. We observe that the BABAR favors $B=0.60$ which has the behavior close to the Chernyak-Zhitnitsky DA, whereas the recent Belle favors $B=0.00$ which is close to the asymptotic DA. We need more accurate data at large $Q^2$ region to determine the precise value of $B$, and the definite behavior of pion DA can be concluded finally by the consistent data in the coming future.