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1.
We consider a cosmological model in which part of the Universe, Ωh～10?5, is in the form of primordial black holes with masses of ～ 105 M ⊙. These primordial black holes were the centers for growing protogalaxies, which experienced multiple mergers with ordinary galaxies and with each other. The galaxy formation is accompanied by the merging and growth of central black holes in the galactic nuclei. We show that the recently discovered correlations between central black hole masses and galactic bulge parameters naturally arise in this scenario.  相似文献   

2.
Two quasars SDSS J010013.02+280225.8 and J030642.51+185315.8 with redshifts z = 6.30 and z = 5.363 were recently discovered. Their apparent magnitudes in the standard cosmological model give the luminosities of Lbol ～ 4.3 × 1014L⊙ and Lbol ～ 3.4 × 1014L⊙. In the framework of modern concepts it is accepted that the energy release of quasars is provided by the accretion onto black holes with masses of 1.24 ± 0.19 × 1010M⊙ and 1.07 ± 0.27 × 1010M⊙. As within the standard cosmological model the ages of these objects are about one billion years, this creates serious difficulties for the scenario of formation of such objects. Here we interpret the ultra-high luminosities of quasars as the effect of lensing of their radiation by the foreground globular clusters or dwarf galaxies.  相似文献   

3.
Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto–Nagai expressions. The Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen–Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ ⊙ = 0.1 M ⊙ pc?3 and the force K z =1.1/2πG = 77 M ⊙ pc?2 acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M G (R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 1012 M ⊙, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, M G (R ≤ 200 kpc) = (1.45 ±0.30)× 1012 M ⊙, M G (R ≤ 200 kpc) = (1.29± 0.14)× 1012 M ⊙ at γ = 6.3, and the smallest value has been found in model II, M G (R ≤ 200 kpc) = (0.61 ± 0.12) × 1012 M ⊙. In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is M G (R ≤ 200 kpc) = (0.75 ± 0.19) × 1012 M ⊙. A comparative analysis with the models by Irrgang et al. (2013), including those using the integration of orbits for the two globular clusters NGC 104 and NGC 1851 as an example, has been performed. The third model is shown to have subjected to a significant improvement.  相似文献   

4.
We have performed hydrodynamic calculations of the radial pulsations of helium stars with masses 10M⊙ ≤ M ≤ 50M⊙, luminosity-to-mass ratios 5 × 103L⊙/M⊙ ≤ L/M ≤ 2.5 × 104L⊙/M⊙, and effective temperatures 2 × 104 K ≤ Teff ≤ 105 K for helium and heavy-element mass fractions of Y=0.98 and Z=0.02, respectively. We show that the high-temperature boundary of the instability region for radial pulsations at L/M ? 104L⊙/M⊙ extends to Teff≈105 K. The amplitude of the velocity variations for outer layers is several hundred km s?1, while the brightness variations in the B band of the UBV photometric system are within the range from several hundredths to half a magnitude. At constant luminosity-to-mass ratio, the radial pulsation period is determined only by the effective temperature of the star. In the ranges of luminosity-to-mass ratios 104L⊙/M⊙ ≤ L/M ≤ 2 × 104L⊙/M⊙ and effective temperatures 5 × 104 K ≤ Teff ≤ 9 × 104 K, the periods of the radial modes are within 6 min ?Π?103 min.  相似文献   

5.
We have obtained new constraints on the cosmological parameters Ω m and σ 8 from the peculiar velocities of flat edge-on spiral galaxies from the RFGC catalog. Based on these results presented graphically, we have found the quantitative condition (Ω m /0.3)0.37 σ 8 = 0.92 ± 0.05. The estimates of Ω m and σ 8, along with their combinations Ω m α σ 8 for various α, are compared with the estimates by other authors.  相似文献   

6.
We consider the possibility of detecting intermediate-mass (103–104 M ⊙) black holes, whose existence at the centers of globular clusters is expected from optical and infrared observations, using precise pulse arrival timing for the millisecond pulsars in globular clusters known to date. For some of these pulsars closest to the cluster centers, we have calculated the expected delay times of pulses as they pass in the gravitational field of the central black hole. The detection of such a time delay by currently available instruments for the known pulsars is shown to be impossible at a black hole mass of 103 M ⊙ and very problematic at a black hole mass of 104 M ⊙. In addition, the signal delay will have a negligible effect on the pulsar periods and their first derivatives compared to the current accuracy of their measurements.  相似文献   

7.
Based on data from the Two-Micrometer All-Sky Survey (2MASS), we analyzed the infrared properties of 451 Local-Volume galaxies at distances D ≤ 10 Mpc. We determined the K-band luminosity function of the galaxies in the range of absolute magnitudes from ?25m to ?11m. The local luminosity density within 8 Mpc is 6.8 × 108L⊙ Mpc?3, a factor of 1.5 ± 0.1 higher than the global mean K-band luminosity density. We determined the ratios of the virial mass to the K-band luminosity for nearby groups and clusters of galaxies. In the luminosity range from 5 × 1010 to 2 × 1013L⊙, the dependence log(M/LK) ∝ (0.27 ± 0.03) log LK with a dispersion of ～0.1 comparable to the measurement errors of the masses and luminosities of the systems of galaxies holds for the groups and clusters of galaxies. The ensemble-averaged ratio, 〈M/LK〉 ? (20–25) M⊙/L⊙, was found to be much smaller than the expected global ratio, (80–90)M⊙/L⊙, in the standard model with Ωm = 0.27. This discrepancy can be eliminated if the bulk of the dark matter in the Universe is not associated with galaxies and their systems.  相似文献   

8.
We study a black hole in an expanding Universe during the radiation-dominated stage. In particular, such a black hole may be of the primordial origin. In the case when the black hole radius is much smaller than the cosmological horizon, we found a self-consistent solution for the metric and the matter distribution and its velocity far from the black hole. At distances much smaller than the cosmological horizon our solution coincides with the previously obtained solution for quasi-stationary accretion. Our results can be applied, in particular, for the formation of dark matter density spikes around primordial black holes, and for the evolution of dark matter clumps during the radiation-dominated stage.  相似文献   

9.
The various measurements of the linear matter density perturbation amplitude obtained from the observations of the cosmic microwave background (CMB) anisotropy, weak gravitational lensing, galaxy cluster mass function, matter power spectrum, and redshift space distortions are compared. The Planck data on the CMB temperature anisotropy spectrum at high multipoles, ? > 1000 (where the effect of gravitational lensing is most significant), are shown to give a measurement of the matter density perturbation amplitude that contradicts all other measurements of this quantity from both Planck CMB anisotropy data and other data at a significance level of about 3.7σ. Thus, at present these data should not be combined together for the calculations of constraints on cosmological parameters. Except for the Planck data on the CMB temperature anisotropy spectrum at high multipoles, all the remaining measurements of the density perturbation amplitude agree well between themselves and give the following constraints: σ8 = 0.792± 0.006 on the linear matter density perturbation amplitude, Ωm = 0.287± 0.007 on the matter density parameter, and H0 = 69.4 ± 0.6 km s?1 Mpc?1 on the Hubble constant. Various constraints on the sum of neutrino masses and the number of neutrino flavors can be obtained by additionally taking into account the data on baryon acoustic oscillations and (or) direct Hubble constant measurements in the local Universe.  相似文献   

10.
Excitation of radial oscillations in population I (X = 0.7, Z = 0.02) red supergiants is investigated using the solution of the equations of radiation hydrodynamics and turbulent convection. The core helium burning stars with masses 8M ⊙ ≤ M ≤ 20M ⊙ and effective temperatures T eff < 4000 K are shown to be unstable against radial pulsations in the fundamental mode. The oscillation periods range between 45 and 1180 days. The pulsational instability is due to the κ-mechanism in the hydrogen and heliumionization zones. Radial pulsations of stars with mass M < 15M ⊙ are strictly periodic with the light amplitude ΔM bol ≤ 0?5. The pulsation amplitude increases with increasing stellar mass and for M > 15M ⊙ the maximum expansion velocity of outer layers is as high as one third of the escape velocity. The mean radii of outer Lagrangean mass zones increase due to nonlinear oscillations by ≤30% in comparison with the initial equilibrium. The approximate method (with uncertainty of a factor of 1.5) to evaluate the mass of the pulsating red supergiant with the known period of radial oscillations is proposed. The approximation of the pulsation constant Q as a function of the mass-to-radius ratio is given. Masses of seven galactic red supergiants are evaluated using the period-mean density relation.  相似文献   

11.
Stellar evolution calculations were carried out from the main sequence to the final stage of the asymptotic giant branch for stars with initial masses 1 M⊙ ≤ MZAMS ≤ 2 M⊙ and metallicity Z = 0.01. Selected models of evolutionary sequences were used as initial conditions for solution of the equations of radiation hydrodynamics and time–dependent convection describing radial stellar pulsations. The study was aimed to construct the hydrodynamic models of Mira–type stars that show the secular decrease in the pulsation period Π commenced in 1970th at Π = 315 day. We show that such a condition for the period change is satisfied with evolutionary sequences 1 M⊙ ≤ MZAMS ≤ 1.2 M⊙ and the best agreement with observations is obtained for MZAMS = 1.2 M⊙. The pulsation period reduction is due to both the stellar radius decrease during the thermal pulse of the helium burning shell and mode switch from the fundamental mode to the first overtone. Theoretical estimates of the fundament parameters of the star at the onset of pulsation period reduction are as follows: the mass is M = 0.93 M⊙, the luminosity is L = 4080 L⊙, and the radius is R = 220 R⊙. The mode switch occurs 35 years after the onset of period reduction.  相似文献   

12.
In recent years, the thermodynamic properties of black holes are topics of interests. We investigate the thermodynamic properties like surface gravity and Hawking temperature on event horizon of regular black holes viz. Hayward Class and asymptotically AdS (Anti-de Sitter) black holes. We also analyze the thermodynamic volume and naive geometric volume of asymptotically AdS black holes and show that the entropy of these black holes is simply the ratio of the naive geometric volume to thermodynamic volume. We plot the different graphs and interpret them physically. We derive the ‘cosmic-Censorship-Inequality’ for both type of black holes. Moreover, we calculate the thermal heat capacity of aforesaid black holes and study their stabilities in different regimes. Finally, we compute the logarithmic correction to the entropy for both the black holes considering the quantum fluctuations around the thermal equilibrium and study the corresponding thermodynamics.  相似文献   

13.
The parameters of the cosmological model with cold dark matter and cosmological constant (ΛCDM model) were determined using three-year Wilkinson Microwave Anisotropy Probe observations of cosmic microwave background together with some data on the large-scale structure of the universe. The data cover scales from 1 to 10 000 Mpc. The best-fit ΛCDM model parameters were derived by minimizing the x 2 statistic with the use of the Levenberg-Markquardt approach (ΩΛ = 0.736 ± 0.065, Ωm = 0.238 ± 0.080, Ωb = 0.05 ± 0.011, h = 0.68 ± 0.09, σ8 = 0.73 ± 0.08, and n s = 0.96 ± 0.015). The ΛCDM model with these parameters is shown to agree well with the angular power spectrum of cosmic microwave background temperature fluctuations and with the density perturbation power spectra estimated from spatial distributions of galaxies and rich clusters of galaxies as well as from the statistics of the Ly α absorption lines in the spectra of distant quasars. The accord between the model large-scale structure characteristics and the observed ones is analyzed, and conceivable factors causing appreciable discrepancies between some characteristics are discussed.  相似文献   

14.
We present the results of solving the radiative transfer equation for the Stokes vector in the case of light scattering by spherical forsterite dust particles in an axisymmetric circumstellar envelope of a red giant. We have assumed that the surfaces of constant scattering-particle density are prolate or oblate spheroids, the particle density decreases with radius as N d ∝ r −2, and the dust particles at the inner boundary of the envelope are in thermal equilibrium with the stellar emission at solid-phase evaporation temperature T ev = 800 K. In the wavelength range 0.27 μm ≤ λ ≤ 1 μm, particles with radii 0.03 μm ≲ a ≲ 0.2 μm make a major contribution to the linear polarization of the stellar emission. The increase in scattering efficiency factor with decreasing wavelength λ is mainly responsible for the growth of polarization toward the short wavelengths known from observations. However, at a mean number of scatterings 1.2 ≤ N sca ≤ 1.6, the polarization ceases to grow due to depolarization effects and decreases rapidly as the wavelength decreases further. The wavelength of the polarization maximum is determined mainly by two quantities: the particle radius and the mass loss rate. The upper limits for the degree of linear polarization in the case of light scattering in circumstellar dust envelopes with the geometries of prolate and oblate spheroids are p ≈ 3 and 5%, respectively. The polarization for light scattering by enstatite particles is higher than that for light scattering by forsterite particles approximately by 0.3%. Original Russian Text ? Yu.A. Fadeyev, 2007, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2007, Vol. 33, No. 2, pp. 123–133.  相似文献   

15.
We present the results of our hydrodynamic calculations of radial pulsations in helium stars with masses 1 M⊙ ≤ M ≤ 10 M⊙, luminosity-to-mass ratios 1 × 103L⊙/M⊙ ≤ L/M ≤ 2 × 104L⊙/M⊙, and effective temperatures 2 × 104 K ≤ Teff ≤ 105 K for mass fractions of helium Y=0.98 and heavy elements Z=0.02. We show that the lower boundary of the pulsation-instability region corresponds to L/M ～ 103L⊙/M⊙ and that the instability region for L/M ? 5 × 103L⊙/M⊙ is bounded by effective temperatures Teff ? 3 × 104 K. As the luminosity rises, the instability boundary moves into the left part of the Hertzsprung-Russell diagram and radial pulsations can arise in stars with effective temperatures Teff ? 105 K at L/M ? 7 × 103L⊙/M⊙. The velocity amplitude for the outer boundary of the hydrodynamic model increases with L/M and lies within the range 200 ? ΔU ? 700 km s?1 for the models under consideration. The periodic shock waves that accompany radial pulsations cause a significant change of the gas-density distribution in the stellar atmosphere, which is described by a dynamic scale height comparable to the stellar radius. The dynamic instability boundary that corresponds to the separation of the outer stellar atmospheric layers at a superparabolic velocity is roughly determined by a luminosity-to-mass ratio L/M ～ 3 × 104L⊙/M⊙.  相似文献   

16.
Evolutionary tracks from the zero age main sequence to the asymptotic giant branch were computed for stars with initial masses 2 M ⊙ ≤ M ZAMS ≤ 5 M ⊙ and metallicity Z = 0.02. Some models of evolutionary sequences were used as initial conditions for equations of radiation hydrodynamics and turbulent convection describing radial stellar pulsations. The early asymptotic giant branch stars are shown to pulsate in the fundamental mode with periods 30 day ? Π ? 400day. The rate of period change gradually increases as the star evolves but is too small to be detected (Π?/Π < 10?5 yr?1). Pulsation properties of thermally pulsing AGB stars are investigated on time intervals comprising 17 thermal pulses for evolutionary sequences with initial masses M ZAMS = 2 M ⊙ and 3 M ⊙ and 6 thermal pulses for M ZAMS = 4 M ⊙ and 5 M ⊙. Stars with initial masses M ZAMS ≤ 3 M ⊙ pulsate either in the fundamental mode or in the first overtone, whereas more massive red giants (M ZAMS ≥ 4 M ⊙) pulsate in the fundamental mode with periods Π ? 103 day. Most rapid pulsation period change with rate ?0.02 yr?1 ? Π?/Π ? ?0.01 yr?1 occurs during decrease of the surface luminosity after the maximum of the luminosity in the helium shell source. The rate of subsequent increase of the period is Π?/Π ? 5 × 10?3 yr?1.  相似文献   

17.
Small perturbations of spherical star clusters around massive black holes are studied. The presence of a black hole gives rise to peculiar distributions that have no stars with low angular momenta (falling into the so-called “loss cone”). The stability of such a distribution has been found to depend significantly on whether it monotonically increases with angular momentum L (from the loss cone up to L = L circ in circular orbits) or has a maximum at some intermediate L = L *. In the case of spherical systems under consideration, the loss-cone instability is shown to be possible only for nonmonotonic distributions.  相似文献   

18.
Speckle interferometric observations made with the 6 m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in 2000 revealed the triple nature of the nearby (π Hip = 51.80 ± 1.74 mas) low-mass young (≈ 200 Myr) star GJ 900. The configuration of the triple system allowed it to be dynamically unstable. Differential photometry performed from 2000 through 2004 yielded I- and K-band absolute magnitudes and spectral types for the components to be I A =6.66±0.08, I B =9.15±0.11, I C =10.08±0.26, K A =4.84±0.08, K B =6.76±0.20, K C =7.39±0.31, Sp A ≈K5?K7, Sp B ≈M3?M4, Sp C ≈M5?M6. The “mass-luminosity” relation is used to estimate the individual masses of the components: M A ≈0.64M ⊙, M B ≈0.21M ⊙, M C ≈0.13M ⊙. From the observations of the components’ relative motion in the period 2000–2006, we conclude that GJ 900 is a hierarchical triple star with the possible orbital periods PA-BC≈80 yrs and PBC≈20 yrs. An analysis of the 2MASS images of the region around GJ 900 leads us to suggest that the system can include other very-low-mass components.  相似文献   

19.
In this paper we extend the idea suggested previously by Pétri (Astron. Astrophys. 439:L27, 2005a; 443:777, 2005b) (papers I and II) that the high frequency quasi-periodic oscillations (HF-QPOs) observed in low-mass X-ray binaries (LMXBs) may be explained as a resonant oscillation of the accretion disk with a rotating asymmetric background (gravitational or magnetic) field imposed by the compact object. Here, we apply this general idea to black hole binaries. It is assumed that a test particle experiences a similar parametric resonance mechanism such as the one described in paper I and II but now the resonance is induced by the interaction between a spiral density wave in the accretion disk, excited close to the innermost stable circular orbit, and vertical epicyclic oscillations. We use the Kerr spacetime geometry to deduce the characteristic frequencies of this test particle. The response of the test particle is maximal when the frequency ratio of the two strongest resonances is equal to 3:2 as observed in black hole candidates. Finally, applying our model to the microquasar GRS 1915+105, we reproduce the correct value of several HF-QPOs. Indeed the presence of the 168/113/56/42/28 Hz features in the power spectrum time analysis is predicted. Moreover, based only on the two HF-QPO frequencies, our model is able to constrain the mass M BH and angular momentum a BH of the accreting black hole. We show the relation between M BH and a BH for several black hole binaries. For instance, assuming a black hole weakly or mildly rotating, i.e. a BH≤0.5?G? M BH/c 2, we find that for GRS 1915+105 its mass satisfies 13?M ⊙≤M BH≤20?M ⊙. The same model applied to two other well-known BHCs gives for GRO J1655-40 a mass 5?M ⊙≤M BH≤7?M ⊙ and for XTE J1550-564 a mass 8?M ⊙≤M BH≤11?M ⊙. This is consistent with other independent estimations of the black hole mass. Finally for H1743-322, we found the following bounds, 9?M ⊙≤M BH≤13?M ⊙.  相似文献   

20.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30%: (U, V,W)⊙ = (8.16, 11.19, 8.55)± (0.48, 0.56, 0.48) km s?1, Ω0 = 28.92 ± 0.39 km s?1 kpc?1, Ω'0 = ?4.087 ± 0.083 km s?1 kpc?2, and Ω″ 0 = 0.703 ± 0.067 km s?1 kpc?3, where the circular velocity of the local standard of rest is V0 = 231 ± 5 km s?1 (for the adopted R0 = 8.0 ± 0.15 kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, VR, residual tangential, ΔVcirc, and vertical, W, velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are fR = 7.1± 0.3 km s?1, fθ = 6.5 ± 0.4 km s?1, and fW = 4.8± 0.8 km s?1, respectively; the perturbation wavelengths are λR = 3.3 ± 0.1 kpc, λθ = 2.3 ± 0.2 kpc, and λW = 2.6 ± 0.5 kpc; and the Sun’s radial phase in the spiral density wave is (χ⊙)R = ?135? ± 5?, (χ⊙)θ = ?123? ± 8?, and (χ⊙)W = ?132? ± 21? for the adopted four-armed spiral pattern.  相似文献   

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