16271202
Supermassive black hole masses of AGNs with elliptical hosts
The recently discovered tight correlation between supermassive black hole mass and central velocity dispersion for both inactive and active galaxies suggests a possibility to estimate the black hole mass from the measured central velocity dispersion. However, for most AGNs it is difficult to measure the central velocity dispersions of their host galaxies directly with spectroscopic studies. In this paper we adopt the fundamental plane for ellipticals to estimate the central velocity dispersion and black hole mass for a number of AGNs with morphology parameters of their elliptical host galaxies obtained by the Hubble Space Telescope imaging observations. The estimated black hole masses of 63 BL Lac objects, 10 radio galaxies, 10 radio-loud quasars and 9 radio-quiet quasars are mostly in the range of $10^{7.5}~M_\odot$ to $10^{9}~ M_\odot$. No significant difference in black hole mass is found for high-frequency peaked BL Lacs and low-frequency peaked BL Lacs, as well as for radio galaxies and radio-loud quasars. The Eddington ratios of radio galaxies are substantially smaller than those of quasars. This suggests that the different observational features of these radio-loud AGNs may be mainly dominated by different accretion rate rather than by the black hole mass, which is in agreement with some evolutionary scenarios recently proposed for radio-loud AGNs. Different to some previous claims, we found that the derived mean black hole mass for radio-loud quasars is only slightly larger than that of radio-quiet quasars. Though the black hole mass distributions between radio-loud and radio-quiet quasars are statistically different, their Eddington ratio distributions are probably from the same population. In addition, we noted that the relation between black hole mass and host galaxy luminosity we obtained using the fundamental plane provides further arguments for a nonlinear scaling law between supermassive black hole mass and galactic bulge mass.
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.
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.
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
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.
118629237
Limits from Weak Gravity Conjecture on Dark Energy Models
The weak gravity conjecture has been proposed as a criterion to distinguish the landscape from the swampland in string theory. As an application in cosmology of this conjecture, we use it to impose theoretical constraint on parameters of two types of dark energy models. Our analysis indicates that the Chaplygin-gas-type models realized in quintessence field are in the swampland, whereas the $a$ power-low decay model of the variable cosmological constant can be viable but the parameters are tightly constrained by the conjecture.
119262290
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
We study the pion leading-twist distribution amplitude (DA) within the framework of Shifman-VainshteinZakharov sum rules under the background field theory. To improve the accuracy of the sum rules, we expand both the quark propagator and the vertex dz D. _ n of the correlator up to dimension-six operators in the background field theory. The sum rules for the pion DA moments are obtained, in which all condensates up to dimension-six have been taken into consideration. Using the sum rules, we obtain h.2 ij1 GeV 0.338 +/- 0.032, h.4 ij1 GeV 0.211 +/- 0.030 and h.6 ij1 GeV 0.163 +/- 0.030. It is shown that the dimension-six condensates shall provide sizable contributions to the pion DA moments. We show that the first Gegenbauer moment of the pion leading-twist DA is ap2 j1 GeV 0.403 +/- 0.093, which is consistent with those obtained in the literature within errors but prefers a larger central value as indicated by lattice QCD predictions.
119269475
Doubly Heavy Baryon Production at A High Luminosity $e^+ e^-$ Collider
Within the framework of nonrelativistic QCD, we make a detailed discussion on the doubly heavy baryon production through the $e^+ e^-$ annihilation channel, $e^{+}e^{-}\rightarrow\gamma/Z^0 \rightarrow \Xi_{QQ^{\prime}} +\bar{Q} +\bar{Q^{\prime}}$, at a high luminosity $e^{+}e^{-}$ collider. Here $Q^{(\prime)}$ stands for the heavy $b$ or $c$ quark. In addition to the channel through the usually considered diquark state $(QQ^{\prime})[^3S_1]_{\bf\bar{3}}$, contributions from the channels through other same important diquark states such as $(QQ^{\prime})[^1S_0]_{\bf 6}$ have also been discussed. Uncertainties for the total cross sections are predicted by taking $m_c=1.80\pm0.30$ GeV and $m_b=5.10\pm0.40$ GeV. At a super $Z$-factory running around the $Z^0$ mass and with a high luminosity up to ${\cal L} \propto 10^{34}\sim 10^{36}{\rm cm}^{-2} {\rm s}^{-1}$, we estimate that about $1.1\times10^{5 \sim 7}$ $\Xi_{cc}$ events, $2.6\times10^{5 \sim 7}$ $\Xi_{bc}$ events and $1.2\times 10^{4 \sim 6}$ $\Xi_{bb}$ events can be generated in one operation year. Such a $Z$-factory, thus, will provide a good platform for studying the doubly heavy baryons in comparable to the CERN large hadronic collider.
53329928
Application of the Principle of Maximum Conformality to Top-Pair Production
at the Tevatron and LHC even for the present NNLO level. The Principle of Maximum Conformality (PMC) eliminates the renormalization scale ambiguity in precision tests of Abelian QED and non-Abelian QCD theories. By using the PMC, all nonconformal {βi}-terms in the perturbative expansion series are summed into the running coupling constant, and the resulting scale-fixed predictions are independent of the renormalization scheme. The correct scale-displacement between the arguments of different renormalization schemes is automatically set, and the number of active flavors nf in the {βi}-function is correctly determined. The PMC is consistent with the renormalization group property that a physical result is independent of the renormalization scheme and the choice of the initial renormalization scale μ r . The PMC scale μ r is unambiguous at finite order. Any residual dependence on μ init r for a finite-order calculation will be highly suppressed since the unknown higher-order {βi}-terms will be absorbed into the PMC scales’ higher-order perturbative terms. We find that such renormalization group invariance can be satisfied to high accuracy for σtt̄ at the NNLO level. In this paper we apply PMC scale setting to predict the tt̄ cross-section σtt̄ at the Tevatron and LHC colliders. It is found that σtt̄ remains almost unchanged by varying μ init r within the region of [mt/4, 4mt]. The convergence of the expansion series is greatly improved. For the (qq̄)-channel, which is dominant at the Tevatron, its NLO PMC scale is much smaller than the top-quark mass in the small x-region, and thus its NLO cross-section is increased by about a factor of two. In the case of the (gg)-channel, which is dominant at the LHC, its NLO PMC scale slightly increases with the subprocess collision energy √ s, but it is still smaller than mt for √ s ∼ 1 TeV, and the resulting NLO cross-section is increased by ∼ 20%. As a result, a larger σtt̄ is obtained in comparison to the conventional scale setting method, which agrees well with the present Tevatron and LHC data. More explicitly, by setting mt = 172.9 ± 1.1 GeV, we predict σTevatron, 1.96 TeV = 7.626 +0.265 −0.257 pb, σLHC, 7TeV = 171.8 +5.8 −5.6 pb and σLHC, 14 TeV = 941.3 +28.4 −26.5 pb.
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.