The velocity profiles and properties of proto-magnetar winds are investigated. It is found that the corotation of wind matter with magnetic field lines significantly affects r-process nucleosynthesis and could lead to...The velocity profiles and properties of proto-magnetar winds are investigated. It is found that the corotation of wind matter with magnetic field lines significantly affects r-process nucleosynthesis and could lead to long duration γ-ray bursts and hyper-energetic supernovae.展开更多
We present different mass ratio distributions of massive black hole (MBH) binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has ...We present different mass ratio distributions of massive black hole (MBH) binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has three stages: the dynamical friction stage, the stellar scattering or circumbinary disk stage, and the gravitational radiation stage. The second stage was once believed to be the "final parsec problem" (FPP) as the binary stalled at this stage because of the depletion of stars. Now, the FPP has been shown to no longer be a problem. Here we get two different mass ratio distributions of MBH binaries under two mechanisms, stellar scattering and the cir- cumbinary disk interaction. For the circumbinary disk mechanism, we assume that the binary shrinks by interaction with a circumbinary disk and the two black holes (BHs) have different accretion rates in the simulation. We apply this simple assumption to the hierarchical coevolution model of MBHs and dark matter halos, and we find that there will be more equal-mass MBH binaries in the final coalescence for the case where the circumbinary mechanism operates. This is mainly because the secondary BH in the circumbinary disk system accretes at a higher rate than the primary one.展开更多
Feedback from supernovae (SNe) and from active galactic nuclei (AGN) accom- panies the history of star formation and galaxy evolution. We present an analytic model to explain how and when the SNe and AGN exert the...Feedback from supernovae (SNe) and from active galactic nuclei (AGN) accom- panies the history of star formation and galaxy evolution. We present an analytic model to explain how and when the SNe and AGN exert their feedback effects on the star formation and galaxy evolution processes. By using SNe and AGN kinetic feedback mechanisms based on the Lambda Cold Dark Matter (LCDM) model, we explore how these feedback mecha- nisms affect the star formation history (SFH), the Near-Infrared Background (NIRB) flux and the cosmological reionization. We find the values of the feedback strengths, εAGN = 1.0 -0.03^+0.5 and εSN = 0.04 -0.02^+0.02, can provide a reasonable explanation of most of the observational resuits, and that the AGN feedback effect on star formation history is quite different from the SNe feedback at high redshifts. Our conclusions manifest quantitatively that these feedback effects decrease star formation rate density (SFRD) and the NIRB flux (in 1.4 - 4.0 μm), and postpone the time of completion of the cosmological reionization.展开更多
By employing an improved simulation of the evolution of black holes (BHs) based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ* at hi...By employing an improved simulation of the evolution of black holes (BHs) based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ* at high redshift z ≥ 6 and quantify the mini-QSO's (with BH mass M = 200 - 105M⊙) contribution to cosmic reionization. The simulation demonstrates how seed BHs migrate onto the MBH-σ* relation by merging with each other and accreting gas at z ≥ 6: 1. The correlation between BHs and their host halos increases as the BHs grow; 2. The slope, i.e. Ф = dlog(Mbh)/dlog(σ*) in the relationship, is insensitive to the redshift at z 〉 6. In agreement with previous work, we find that mini-QSOs' ionizing capability to the Universe lies in the range - 25% - 50% if early miniquasars have extremely high duty cycles, i.e. P(z 〉 6) - 0.9 - 1.展开更多
The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the...The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the disk are Comptonized to high energy in the hot corona, and the hard X-ray spectra (lu- minosity and spectral shape) contain information on the incident spectra from the disk. The values of black hole spin parameter a. are inferred from the spectral fitting, which are spread over a large range, ~ -0.94 to 0.998. We find that the inclination angles and mass accretion rates are well determined by the spectral fitting, but the results are sensitive to the accuracy of black hole mass estimates. No tight constraints on the black hole spins are achieved, if the uncertainties in black hole mass measurements are a factor of four, which are typical for the single-epoch reverberation mapping method. Recently, the accuracy of black hole mass measurement has been significantly improved to 0.2 - 0.4 dex with the velocity resolved reverber- ation mapping method. The black hole spin can be well constrained if the mass measurement accuracy is 50%. In the accretion disk corona scenario, a fraction of power dissipated in the disk is transported into the corona, and therefore the accretion disk is thinner than a bare disk for the same mass accretion rate, because the radiation pressure in the disk is reduced. We find that the thin disk approximation, H/R ≤0. 1, is still valid if 0.3 〈 m 〈 0.5, provided half of the dissipated power is radiated in the corona above the disk.展开更多
We study the interaction between supermassive binary black holes in an elliptical orbit and their surrounding disk with a gap. The gap in the disk is a low density region formed due to the tidal effects of the less ma...We study the interaction between supermassive binary black holes in an elliptical orbit and their surrounding disk with a gap. The gap in the disk is a low density region formed due to the tidal effects of the less massive black hole. The binary we have investigated has a sub-parsec separation and is coplanar with the disk. We find that the maximum variation of the surface density in the gap reaches 50% during an orbital period. However, in other regions of the disk, the density variation is much less than 1%. Furthermore, we calculate the corresponding variation of spectral energy distribution within a period, but little variation is found. The reason for these results is that the viscosity timescale of the disk at the binary radius is much longer than the orbital period of the binary.展开更多
基金supported by the National Basic Research Program of China(2009CB824800)the research grants of Changsha University of Science and Technology
文摘The velocity profiles and properties of proto-magnetar winds are investigated. It is found that the corotation of wind matter with magnetic field lines significantly affects r-process nucleosynthesis and could lead to long duration γ-ray bursts and hyper-energetic supernovae.
基金Supported by the National Natural Science Foundation of China
文摘We present different mass ratio distributions of massive black hole (MBH) binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has three stages: the dynamical friction stage, the stellar scattering or circumbinary disk stage, and the gravitational radiation stage. The second stage was once believed to be the "final parsec problem" (FPP) as the binary stalled at this stage because of the depletion of stars. Now, the FPP has been shown to no longer be a problem. Here we get two different mass ratio distributions of MBH binaries under two mechanisms, stellar scattering and the cir- cumbinary disk interaction. For the circumbinary disk mechanism, we assume that the binary shrinks by interaction with a circumbinary disk and the two black holes (BHs) have different accretion rates in the simulation. We apply this simple assumption to the hierarchical coevolution model of MBHs and dark matter halos, and we find that there will be more equal-mass MBH binaries in the final coalescence for the case where the circumbinary mechanism operates. This is mainly because the secondary BH in the circumbinary disk system accretes at a higher rate than the primary one.
文摘Feedback from supernovae (SNe) and from active galactic nuclei (AGN) accom- panies the history of star formation and galaxy evolution. We present an analytic model to explain how and when the SNe and AGN exert their feedback effects on the star formation and galaxy evolution processes. By using SNe and AGN kinetic feedback mechanisms based on the Lambda Cold Dark Matter (LCDM) model, we explore how these feedback mecha- nisms affect the star formation history (SFH), the Near-Infrared Background (NIRB) flux and the cosmological reionization. We find the values of the feedback strengths, εAGN = 1.0 -0.03^+0.5 and εSN = 0.04 -0.02^+0.02, can provide a reasonable explanation of most of the observational resuits, and that the AGN feedback effect on star formation history is quite different from the SNe feedback at high redshifts. Our conclusions manifest quantitatively that these feedback effects decrease star formation rate density (SFRD) and the NIRB flux (in 1.4 - 4.0 μm), and postpone the time of completion of the cosmological reionization.
基金partially supported by the National Basic Research Program of China(2009CB824800)the National Natural Science Foundation of China(Grant Nos.10733010,10673010 and 10573016)the Program for New Century Excellent Talents in University
文摘By employing an improved simulation of the evolution of black holes (BHs) based on the merger tree of dark matter halos, we explore the relationship between the central BH mass Mbh and velocity dispersion σ* at high redshift z ≥ 6 and quantify the mini-QSO's (with BH mass M = 200 - 105M⊙) contribution to cosmic reionization. The simulation demonstrates how seed BHs migrate onto the MBH-σ* relation by merging with each other and accreting gas at z ≥ 6: 1. The correlation between BHs and their host halos increases as the BHs grow; 2. The slope, i.e. Ф = dlog(Mbh)/dlog(σ*) in the relationship, is insensitive to the redshift at z 〉 6. In agreement with previous work, we find that mini-QSOs' ionizing capability to the Universe lies in the range - 25% - 50% if early miniquasars have extremely high duty cycles, i.e. P(z 〉 6) - 0.9 - 1.
基金supported by the National Natural Science Foundation of China(Grant Nos.11173043,11121062,11233006,11073020,11373056 and 11473054)the Fundamental Research Funds for the Central Universities(WK2030220004)+1 种基金the CAS/SAFEA International Partnership Program for Creative Research Teams(KJCX2-YW-T23)Shanghai Municipality
文摘The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the disk are Comptonized to high energy in the hot corona, and the hard X-ray spectra (lu- minosity and spectral shape) contain information on the incident spectra from the disk. The values of black hole spin parameter a. are inferred from the spectral fitting, which are spread over a large range, ~ -0.94 to 0.998. We find that the inclination angles and mass accretion rates are well determined by the spectral fitting, but the results are sensitive to the accuracy of black hole mass estimates. No tight constraints on the black hole spins are achieved, if the uncertainties in black hole mass measurements are a factor of four, which are typical for the single-epoch reverberation mapping method. Recently, the accuracy of black hole mass measurement has been significantly improved to 0.2 - 0.4 dex with the velocity resolved reverber- ation mapping method. The black hole spin can be well constrained if the mass measurement accuracy is 50%. In the accretion disk corona scenario, a fraction of power dissipated in the disk is transported into the corona, and therefore the accretion disk is thinner than a bare disk for the same mass accretion rate, because the radiation pressure in the disk is reduced. We find that the thin disk approximation, H/R ≤0. 1, is still valid if 0.3 〈 m 〈 0.5, provided half of the dissipated power is radiated in the corona above the disk.
基金Supported by the National Natural Science Foundation of China
文摘We study the interaction between supermassive binary black holes in an elliptical orbit and their surrounding disk with a gap. The gap in the disk is a low density region formed due to the tidal effects of the less massive black hole. The binary we have investigated has a sub-parsec separation and is coplanar with the disk. We find that the maximum variation of the surface density in the gap reaches 50% during an orbital period. However, in other regions of the disk, the density variation is much less than 1%. Furthermore, we calculate the corresponding variation of spectral energy distribution within a period, but little variation is found. The reason for these results is that the viscosity timescale of the disk at the binary radius is much longer than the orbital period of the binary.