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1.
The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass
surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution
are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with
a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations.
Different sets of parameters are shown to exist for the gravitationally lensed system B0218+357 in multicomponentmodels. These
sets allow the observed geometry of the system and the intensity ratio of the compact core images to be obtained, but they
lead to a significant spread in the Hubble constant determined from the modeling results. 相似文献
2.
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
3.
Astronomy Reports - A comparison of the virial parameters of galaxies and galaxy clusters (radius, density, and entropy function) in a wide range of masses, $${{10}^{6}} \leqslant... 相似文献
4.
The prospects for observations of gravitationally lensed extragalactic sources in the far-infrared and submillimeter ranges of the electromagnetic spectrum by the planned space observatories with active cooling of the telescope mirror to cryogenic temperatures are considered. The possibility of solving topical cosmological and astrophysical problems related to the observations of gravitationally lensed sources is discussed. The number counts of lensed sources have been performed for various wavelengths in the range from 70 to 2000 µm. The redshift and magnification distributions of lensed sources and the mass distribution of lenses have been obtained. We have constructed model photometric sky maps for which the contribution from lensed sources has been calculated for the first time.
相似文献5.
A prolonged timing of millisecond pulsars has revealed low-frequency uncorrelated (infrared) noise, presumably of astrophysical
origin, in the pulse arrival time (PAT) residuals for some of them. Currently available pulsar timing methods allow the statistical
parameters of this noise to be reliably measured by decomposing the PAT residual function into orthogonal Fourier harmonics.
In most cases, pulsars in globular clusters show a low-frequency modulation of their rotational phase and spin rate. The relativistic
time delay of the pulsar signal in the curved spacetime of randomly distributed and moving globular cluster stars (the Shapiro
effect) is suggested as a possible cause of this modulation. Extremely important (from an astrophysical point of view) information
about the structure of the globular cluster core, which is inaccessible to study by other observational methods, could be
obtained by analyzing the spectral parameters of the low-frequency noise caused by the Shapiro effect and attributable to
the random passages of stars near the line of sight to the pulsar. Given the smallness of the aberration corrections that
arise from the nonstationarity of the gravitational field of the randomly distributed ensemble of stars under consideration,
a formula is derived for the Shapiro effect for a pulsar in a globular cluster. The derived formula is used to calculate the
autocorrelation function of the low-frequency pulsar noise, the slope of its power spectrum, and the behavior of the σz statistic that characterizes the spectral properties of this noise in the form of a time function. The Shapiro effect under
discussion is shown to manifest itself for large impact parameters as a low-frequency noise of the pulsar spin rate with a
spectral index of n = −1.8 that depends weakly on the specific model distribution of stars in the globular cluster. For small impact parameters,
the spectral index of the noise is n = −1.5. 相似文献
6.
A. N. Semena M. G. Revnivtsev T. I. Larchenkova A. A. Lutovinov 《Astronomy Letters》2017,43(10):677-689
The properties of the aperiodic variability in X-ray binaries with black holes are considered. The power spectra of the luminosity variability for a flat accretion disk that is an emission source with a powerlaw energy spectrum have been modeled. At low frequencies the derived power spectrum has the form of a power law with a slope ? ≈ ?1 and a cutoff at a frequency corresponding to the characteristic frequency of fluctuations at the inner disk edge; at higher frequencies the power spectrum has a complex form. The high-frequency variability is suppressed due to the arrival time delays of photons emerged in different parts of the disk. The presence of azimuthal accretion rate fluctuations in the disk and the disk surface brightness nonuniformity in the observer’s imaginary plane caused by the relativistic effects give rise to an additional variability component at frequencies ～ 200 Hz. 相似文献
7.
The possibility of using lensed relativistic jets on very small angular scales to construct proper models of spiral lens galaxies
and to independently determine the Hubble constant is considered. The system B0218+357 is used as an example to illustrate
that there exists a great choice of model parameters adequately reproducing its observed large-scale properties but leading
to a significant spread in the Hubble constant. The jet image position angle is suggested as an additional parameter that
allows the range of models under consideration to be limited. It is shown that themodels for which the jet image position
angles differ by at least 40° can be distinguished between themselves during observations on very small angular scales. The
possibility of observing the geometric properties of lensed relativistic jets and measuring the superluminal velocities of
knot images on time scales of several months with very long baseline space interferometers is discussed. 相似文献
8.
For pulsars in globular clusters, we suggest using observations of the relativistic time delay of their radiation in the gravitational field of a massive body (the Shapiro effect) located close to the line of sight to detect and identify invisible compact objects and to study the distribution of both visible and dark matter in globular clusters and different components of the Galaxy. We have derived the dependences of the event probability on the Galactic latitude and longitude of sources for two models of the mass distribution in the Galaxy: the “classical” Bahcall—Soneira model and the more recent Dehnen—Binney model. Using three globular clusters (M15, 47 Tuc, Terzan 5) as an example, we show that the ratios of the probability of the events due to the passages of massive Galactic objects close to the line of sight to the parameter f 2 for pulsars in the globular clusters 47 Tuc and M 15 are comparable to those for close passages of massive objects in the clusters themselves and are considerably higher than those for the cluster Terzan 5. We have estimated the rates of such events. We have determined the number of objects near the line of sight toward the pulsar that can produce a modulation of its pulse arrival times characteristic of the effect under consideration; the population of brown dwarfs in the Galactic disk, whose concentration is comparable to that of the disk stars, has been taken into account for the first time. 相似文献
9.
S. V. Pilipenko M. V. Tkachev A. A. Ermash T. I. Larchenkova E. V. Mikheeva V. N. Lukash 《Astronomy Letters》2017,43(10):644-655
The extragalactic background radiation produced by distant galaxies emitting in the far infrared limits the sensitivity of telescopes operating in this range due to confusion. We have constructed a model of the infrared background based on numerical simulations of the large-scale structure of the Universe and the evolution of dark matter halos. The predictions of this model agree well with the existing data on source counts. We have constructed maps of a sky field with an area of 1 deg2 directly from our simulated observations and measured the confusion limit. At wavelengths 100–300 μm the confusion limit for a 10-m telescope has been shown to be at least an order of magnitude lower than that for a 3.5-m one. A spectral analysis of the simulated infrared background maps clearly reveals the large-scale structure of the Universe. The two-dimensional power spectrum of these maps has turned out to be close to that measured by space observatories in the infrared. However, the fluctuations in the number of intensity peaks observed in the simulated field show no clear correlation with superclusters of galaxies; the large-scale structure has virtually no effect on the confusion limit. 相似文献
10.
Astronomy Letters - We propose a method of analyzing the absorption spectra of quasars that allows the physical parameters of absorbing clouds, absorbers, to be roughly estimated: their masses,... 相似文献