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1.
The Tully–Fisher relationship (TFR) has been shown to have a relatively small observed scatter of ∼±0.35 mag implying an intrinsic
scatter < ±0.30 mag. However, when the TFR is calibrated from distances derived from the Hubble relation for field galaxies
scatter is consistently found to be ±0.64 to ±0.84 mag. This significantly larger scatter requires that intrinsic TFR scatter
is actually much larger than ±0.30 mag, that field galaxies have an intrinsic TFR scatter much larger than cluster spirals,
or that field galaxies have a velocity dispersion relative to the Hubble flow in excess of 1000 km s−1. Each of these potential explanations faces difficulties and contradicted by available data and the results of previous studies.
An alternative explanation is that the measured redshifts of galaxies are composed of a cosmological redshift component predicted
from the value of the Hubble constant and a superimposed intrinsic redshift component previously identified in other studies.
This intrinsic redshift component may exceed 5000 km s−1 in individual galaxies. In this alternative scenario a possible value for the Hubble constant is 55–60 km s−1 Mpc−1. 相似文献
2.
Ahmad Rami El-Nabulsi 《Astrophysics and Space Science》2010,325(2):163-175
We processed the data on radial velocities and HI line widths for 1678 flat edge-on spirals from the Revised Flat Galaxy Catalogue.
We obtained the parameters of the multipole components of the large-scale velocity field of collective non-Hubble galaxy motion
as well as the parameters of the generalized Tully–Fisher relation in the “HI line width—linear diameter” version. All the
calculations were performed independently in the framework of three models, where the multipole decomposition of the galaxy
velocity field was limited to a dipole, a quadrupole, and an octopole term. We showed that both the quadrupole and the octopole
components are statistically significant.
On the basis of the compiled list of peculiar velocities of 1623 galaxies we obtained estimations of cosmological parameters
Ω
m
and σ
8. These estimations were obtained in both graphical form and as a constraint of the value S
8=(Ω
m
/0.3)0.35
σ
8=0.91±0.05. 相似文献
3.
It is shown that in the most general version of the bimetric scalar-tensor theory of gravitation, a spherically symmetric
vacuum gravitational field is static if the gravitational scalar does not depend on time. This result is generalized to certain
cases in which a source is present, including an electromagnetic field. Both branches of solutions with a variable and a constant
scalar field are considered.
Translated from Astrofizika, Vol. 40, No. 2, pp. 281–290, April–June, 1997. 相似文献
4.
Corrado Massa 《Astrophysics and Space Science》2006,305(4):377-384
Quantum theory in Robertson – Walker spacetime suggests the existence of a minimal energy ε of the order of 10−45 erg. Reasonable forms for ε give the expansion factor R=R(t)(t= the cosmic time) with no need of gravitational field equations.Einstein's theory should be modified in gravitational fields of strength less than ε c/ħ ∼ 10−8 cm/s2 where c is the speed of light and ħ is the reduced Planck constant. The cosmological term λ is expected to decrease as the universe expands.In the Appendix, ε is derived from a big bang – big crunch Newtonian cosmology. 相似文献
5.
Variant of the bimetric theory of gravitation. II. Energy-momentum tensor of the gravitational field
Starting from the invariance of action relative to coordinate transformations, differential conservation laws are established
in the bimetric theory of gravitation with a Lagrangian that is quadratic with respect to “intensities.” Explicit expressions
are found for the canonical and metric energymomentum tensors of the gravitational field, as well as for the tensor analog
of the Landau-Lifshitz pseudotensor.
Translated from Astrofizika, Vol. 43, No. 3, pp. 493-499, July–September, 2000. 相似文献
6.
Roman Tomaschitz 《Astrophysics and Space Science》2011,331(2):397-408
The effect of a cosmic time variation of Newton’s constant on galactic angular diameters, linear size, apparent magnitude,
and surface brightness is investigated. The redshift scaling of the gravitational constant is proportional to the Hubble parameter,
derived from the constancy of a moderate dimensionless ratio of fundamental constants, and manifested in galactic linear-size
evolution. The latter is demonstrated by fitting the angular size–redshift relation to spectroscopically and photometrically
selected samples of high-redshift rotators. The intrinsic luminosity evolution of the rotators and their magnitude–redshift
and surface brightness–redshift relations are studied. The galactic luminosity scales with a power of the Hubble parameter,
and the scaling exponent is inferred from a moderate dimensionless ratio involving the gravitational constant, the Galactic
luminosity, and the velocity of the Galaxy in the microwave background. The fits are performed with a cosmic expansion factor
derived from paleoplanetary surface temperatures. This expansion factor is tested by comparing the corresponding redshift
evolution of the angular-size distance to the distance estimates of two samples of galaxy clusters. 相似文献
7.
The gravitational field of a global monopole in the context of Einstein–Cartan theory is investigated. A comparison is made
with the corresponding results predicted by general relativity.
PACS Nos: 98.80cq; 04.20 jb; 04.50 相似文献
8.
The gravitational radiation of n = 1 polytropes undergoing quasiradial pulsations is examined. The intensity of the gravitational
radiation and the gravitational wave amplitudes are calculated for polytropic models of white dwarfs and neutron stars when
the energy of rotation of the object serves as the source of the radiated energy. Calculations of h0 show that objects with a polytropic equation of state can describe the expected gravitational radiation from white dwarfs
and neutron stars. The gravitational radiation of polytropic models of galactic nuclei and quasars is also examined. These
objects can create a high enough background of gravitational radiation at frequencies of 10-8–10-11 Hz for gravitational wave detectors operating in this frequency range.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 603–612 (November 2005). 相似文献
9.
Yu. V. Baryshev 《Astrophysics》1997,40(3):244-251
An equation is obtained for the cross section of a metal Weber cylinder for scalar gravitational waves, which are possible
within the framework of the field theory of gravitation. It is shown that the signals detected by the Amaldi and Weber antennas
during the explosion of supernova SN 1987A can be interpreted as the result of the action of scalar gravitational waves on
solid-state detectors. The required energy of the gravitational waves is about 1 M⊙c2. Together with the observed excess (about 1 %) of gravitational radiation from the binary system containing the pulsar PSR
1913+16, the signals from SN 1987A are the second piece of observational evidence for the actual existence of scalar gravitational
waves. The present-day, third-generation, solid-state antennas are capable of detecting scalar waves from events like SN 1987A
at a distance up to 5 Mpc. The expected level of the signal from SN 19931 is about 7 mK. An experimental test of the longitudinal
nature of scalar waves is possible using interferometric antennas based on free masses.
Translated from Astrofizika, Vol. 40, No. 3, pp. 377–389, August, 1997. 相似文献
10.
11.
A model of the early universe in the Einstein theory of gravitation, supplemented by a conformalty invariant version of the
Weinberg—Salam model, is considered. The conformai symmetry principle leads to the need to eliminate the Higgs potential from
the expression for gravitational action, using the Lagrangian density of the model of Weinberg—Salam electroweak interactions
as the material source, and to incorporate the conformally invariant Penrose—Chernikov—Tagirov term. In the limit of flat
space, we arrive at the a version of the Weinberg—Salam model without Higgs particle-like excitations. In the conformalty
invariant model under consideration, Higgs fields are absorbed by the spatial metric, so one can assume that the masses of
elementary particles originate at the time when the evolution of the universe begins.
Translated from Astrofizika, Vol. 41, No. 3, pp. 459–471, July–September, 1998. 相似文献
12.
Confronted with microwave background observations by WMAP and with consternating supernova locations in the magnitude–redshift
diagram modern cosmology feels enforced to call for cosmic vacuum energy as a necessary cosmological ingredient. Most often
this vacuum energy is associated with Einstein’s cosmological constant Λ or with so-called “dark energy”. A positive value
of Λ describes an inflationary action on cosmic dynamics which in view of recent cosmological data appears as an absolute
need. In this article, however, we question the hypothesis of a constant vacuum energy density since not justifiable on physical
grounds. Instead we show that gravitational binding energy of cosmic matter, connected with ongoing structure formation during
cosmic expansion, acts similar to vacuum energy, since it reduces the effective gravitating proper mass density. Thus one
may be encouraged to believe that actions of cosmic vacuum energy and gravitational binding energy concerning their cosmological
effects are closely related to each other, perhaps in some respects even have identical phenomenologies. 相似文献
13.
《New Astronomy》2007,12(2):142-145
We consider a generic minimal modification of the Newtonian potential, that is a modification that introduces only one additional dimensional parameter. The modified potential depends on a function whose behavior for large and small distances can be fixed in order to obtain: (i) galactic flat rotational curves and (ii) a universal constant acceleration independent of the masses of the interacting bodies (Pioneer anomaly). Then using a dimensional argument we show that the Tully–Fisher relation for the maximal rotational velocity of spiral galaxies follows without any further assumptions. This result suggests that the Pioneer anomalous acceleration and the flat rotational curves of galaxies could have a common origin in a modified gravitational theory. The relation of these results with the Modified Newtonian Dynamics (MOND) is discussed. 相似文献
14.
The north – south asymmetries (NSA) of three solar activity indices are derived and mutually compared over a period of more
than five solar cycles (1945 – 2001). A catalogue of the hemispheric sunspot numbers, the data set of the coronal green line
brightness developed by us, and the magnetic flux derived from the NSO/KP data (1975 – 2001) are treated separately within
the discrete low- and mid-latitude zones (5° – 30°, 35° – 60°). The calculated autocorrelations, cross-correlations, and regressions
between the long-term NSA data sets reveal regularities in the solar activity phenomenon. Namely, the appearance of a distinct
quasi-biennial oscillation (QBO) is evident in all selected activity indices. Nevertheless, a smooth behavior of QBO is derived
only when sufficient temporal averaging is performed over solar cycles. The variation in the significance and periodicity
of QBO allows us to conclude that the QBO is not persistent over the whole solar cycle. A similarity in the photospheric and
coronal manifestations of the NSA implies that their mutual relation will also show the QBO. A roughly two-year periodicity
is actually obtained, but again only after significant averaging over solar cycles. The derived cross-correlations are in
fact variable in degree of correlation as well as in changing periodicity. A clear and significant temporal shift of 1 – 2
months in the coronal manifestation of the magnetic flux asymmetry relative to the photospheric manifestation is revealed
as a main property of their mutual correlation. This shift can be explained by the delayed large-scale coronal manifestation
in responding to the emergence of the magnetic flux in the photosphere. The reliability of the derived results was confirmed
by numerical tests performed by selecting different numerical values of the used parameters. 相似文献
15.
The north – south (N – S) asymmetry of solar activity is investigated by using the data on coronal green-line brightness and
total number and total area of sunspots over the period of 1939 – 2001. Typical time variations of the N – S asymmetry are
found to be consonant in these indices. Quasi-biennial oscillations (QBO) of solar activity are well recognizable in the N – S
asymmetry of the examined indices. Moreover, the QBO are much better manifested in the N – S asymmetry of the individual indices
than in the original (N plus S) indices. The time variations of relative QBO power are synchronous for the N – S asymmetry
of various solar activity indices whereas such a synchronization is weaker for the indices themselves. It is revealed that
the relative QBO power found in the N – S asymmetry of the studied indices has a negative correlation with the value of the
N – S asymmetry itself. The findings indicate that the N – S asymmetry should be regarded as a fundamental phenomenon of solar
activity similarly manifested in different activity indices. These findings should be taken into account when any dynamo theory
of solar activity is constructed. 相似文献
16.
M. Anna Lakshmi S. Umapathy O. Prakash V. Vasanth 《Astrophysics and Space Science》2011,332(2):373-378
The paper investigates the effects of thermal conductivity and non-uniform magnetic field on the gravitational instability
of a non-uniformly rotating infinitely extending axisymmetric cylinder in a homogeneous heat conducting medium. The non-uniform
rotation and magnetic field are supposed to act along θ and z directions of the cylinder. It is found that the gravitational instability of this general problem is determined by the same
criterion as obtained by Dhiman and Dadwal (Astrophys. Space Sci. 325(2):195–200, 2010) for the self-gravitating isothermal medium in the presence of non-uniform rotation and magnetic field with the only difference
that adiabatic sound velocity is now replaced by the isothermal sound velocity. It is found that the thermal conductivity
has stabilizing effect on the onset of gravitational instability. Further, the stabilizing/destabilizing effect of the non-uniform
magnetic field on the gravitational instability of heat conducting medium has been discussed and is illustrated by considering
some special forms of the basic magnetic fields. 相似文献
17.
Evolutionary calculations based on realistic equations of state indicate the stratified nature of the distribution of hadron
matter in the interiors of neutron stars. In the proposed model, the stratified structure of a neutron star is treated as
a rigid inert core surrounded by a dynamical layer. The physical basis for the model is the concept of the stellar matter
of the peripheral envelope as an elastic Fermi continuum, the motions of which are described by the equations of nuclear elastodynamics,
proposed in the macroscopic theory of collective processes in laboratory nuclear physics. It is shown that the vibrational
dynamics of a neutron star is characterized by two branches of gravitational—elastic, spheroidal (s-mode) and torsional (t-mode)
nonradial eigenvibrations. Estimates obtained for the periods of global, gravitational nonradial modes suggest that variations
in the intensity of micropulses observed in the millisecond range of the spectra of C-pulsars may be ascribed to these vibrations.
The proposed two-component model of a neutron star enables one to consider a glitch in a pulsar’s radio emission as a starquake
due to the passage of the companion through periastron of the binary system.
Translated from Astrofizika, Vol. 42, No. 2, pp. 235–252, April–June, 1999 相似文献
18.
We study the motion of an infinitesimal mass point under the gravitational action of three mass points of masses μ, 1–2μ and
μ moving under Newton's gravitational law in circular periodic orbits around their center of masses. The three point masses
form at any time a collinear central configuration. The body of mass 1–2μ is located at the center of mass. The paper has
two main goals. First, to prove the existence of four transversal ejection–collision orbits, and second to show the existence
of an uncountable number of invariant punctured tori. Both results are for a given large value of the Jacobi constant and
for an arbitrary value of the mass parameter 0<μ≤1/2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
The chemical composition of the Milky-Way halo is studied on the basis of a sample of metal-poor (logarithmic metallicity
less than –1) globular clusters. The histogram obtained may be interpreted in the terms of the classical galaxy formation
theory of Eggen, Lynden-Bell and Sandage. Interestingly enough, this is in a rough agreement with the data on metallicity
of high-redshift damped Ly-alpha and Ly-alpha forest systems. This may serve the important purpose of constraining the nature
and the formation timescale of MACHOs discovered through gravitational microlensing experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
We examine the possible emission of gravitational waves from white dwarfs undergoing self-similar oscillations driven by the
energy released during relaxation of their differential rotation. Two distributions of the initial angular momentum are considered.
It is assumed that 1% of the energy dissipated by a rotating white dwarf is converted into the energy of self-similar oscillations
and, therefore, into gravitational radiation. The relative amplitude of the gravitational radiation from an isolated white
dwarf at a distance of 50 pc is found to be less than 10−27. The emission from the galactic population of white dwarfs may create a background which overlaps the random cosmological
background of gravitational radiation for the improved decihertz detectors currently being proposed.
__________
Translated from Astrofizika, Vol. 49, No. 2, pp. 231–242 (May 2006). 相似文献