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1.
An approximate metric is found which represents a sphere of matter embedded in a background of dust. The use of this metric in conjunction with the Friedmann equations gives values of for the three possible values ofk as +6×10–36 (k=+1), +3×10–35 (k=0), +10–36 (k=–1). These values depend on data regarding clusters of galaxies, and are probably accurate to within an order of magnitude given the correctness of the assumptions on which their derivation rests.  相似文献   

2.
Intensity, polarization, and cooling rate of the two-photon annihilation radiation are studied in detail in the case of one-dimensional power-law distributions of electrons and positrons, assuming that they occupy the ground Landau level in a strong magnetic fieldB1010–1012 G. Simple analytical expressions for limiting cases are obtained and results of numerical calculations of radiation characteristics are presented. Power-lawe ± distributions ± ± –k are shown to generate power-law spectra of the annihilation radiation atEmc 2 andEmc 2, with indices depending on the direction of radiation. The annihilation spectra at =0 show the largest blue-shifts of their maxima and the hardest high-energy tailsI(Emc 2, =0)E –(k–1). The blue-shifts reduce, and the hard tials steepen, with increasing . At >(2mc 2/E)1/2 the slopes of the high-energy tails rapidly transform to that at =2,I(Emc 2, =/2)E –(2k+3). The direction-integrated spectraS(E) also display the power-law tials at low and high energies,S(Emc 2)E –(k+1). The total annihilation rate and energy losses decrease with decreasingk, being higher than for the isotropice ± power-law distributions at the samek. The radiation is linearly polarized in the plane formed by the magnetic field and wave-vector. The polarization degreeP is maximum atEmc 2:P max0.6 for =/2. Annihilation features and power-law-like hard tails observed in many gamma-ray burst spectra may be associated with the annihilation radiation of the magnetized power-law distributed plasma near neutron stars. Comparison of the observed and theoretical spectra allows one to estimate the power-law index of thee – e +-distribution and the gravitational redshift factor in the radiating region.  相似文献   

3.
Ther-centroids and Franck-Condon factors for the bands of theA 2 –X 2+ of CP,C 3 –X 3 of SiC, andB 2+ –X 2+ of CO+ molecules have been determined. The Franck-Condon factors are evaluated by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained.  相似文献   

4.
The variation of radio luminosity with redshift and its effect on the analysis of the angular size-redshift ( –z) relation for a bright radio source sample (s 178 10Jy) has been investigated. By assuming a power law dependence of luminosity on redshift of the formP (1 +z), it was found that 4.4 (with correlation coefficientr 0.99) for at leastz 0.3. Correction for such a strongP – (1 +z) correlation when considering the –z data for the sample led to a steeper –z slope. This could be explained by assuming linear size evolution of the formD (1 +z)–n withn = 2.8 – 3.3 consistent with both theoretical results and those obtained for more homogeneous source samples.  相似文献   

5.
We develop a self-consistent dynamical model for spherically-symmetric clusters of galaxies. The total mass profile and velocity dispersion profiles of galaxies are derived by taking both, galaxies and intracluster gas, in hydrostatic equilibrium, and by assuming the latter to follow a polytropic distributionT–1. We use the strongest and better established correlations among observed properties of clusters to fix the values of the resulting free parameters, and so, to reduce the general freedom of the model.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

6.
Physical conditions are found for a hot intercloud gas in the nuclei of Seyfert galaxies. The gas temperature is determined by photoionization and Compton-scattering of the shortwave radiation of the nucleus. Using observational data for the coronal emission line [Fe x] 6374 Å, the gas densityn=104cm–3 and temperatureT=106K, typical for the distance 2 pc from the central source, are obtained. It is shown that the intercloud gas is in the state of accretion by the nucleus with a rateM10–2 M yr–1.  相似文献   

7.
Star-like objects are found in Seyfert galaxies Markarian 290, Markarian 298, NGC 1275, and NGC 7469, being connected with the structure peculiarities of the galaxies. The absolute magnitudes of these objects are –16 m M–19 m . It has been supposed that these star formations must stimulate the instability in the disk of the galaxy followed by the matter fall toward the centre of the galaxy. The gas inflow toward the centre will allow the recent star formations and Seyfert nuclei generation.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

8.
Hickson's compact galaxy groups were classified using the statistical criterion which includes the radial velocities of galaxies as well as their relative positions. These groups on the whole and their components are identified as the confident and probable non-chance ones as well as probable and confident chance ones. All confident chance objects have the discordant radial velocities (the differences of radial velocitiesDV [1000; 20000] km s–1). The special class of objects bright discordants is selected. These galaxies have the discordant radial velocities withDV [825; 8440] km s–1 and have a strong tendency to be the brightest components of their groups. The lowest difference of radial velocities for the last class of objects DV = (1.0±0.2) × 103 km s–1 and we accept this value of DV as the lowest value of discordant radial velocities. It is found that the biggest part of Hickson's compact groups consist of non-chance aggregations of galaxies and some of the cases of discordant-redshifts require a special study in order to explain their origin from a dynamic or some other point of view.Present address.  相似文献   

9.
Wheatland  M.S.  Litvinenko  Y.E. 《Solar physics》2002,211(1-2):255-274
The observed distribution of waiting times t between X-ray solar flares of greater than C1 class listed in the Geostationary Operational Environmental Satellite (GOES) catalog exhibits a power-law tail (t) for large waiting times (t>10hours). It is shown that the power-law index varies with the solar cycle. For the minimum phase of the cycle the index is =–1.4±0.1, and for the maximum phase of the cycle the index is –3.2±0.2. For all years 1975–2001, the index is –2.2±0.1. We present a simple theory to account for the observed waiting-time distributions in terms of a Poisson process with a time-varying rate (t). A common approximation of slow variation of the rate with respect to a waiting time is examined, and found to be valid for the GOES catalog events. Subject to this approximation the observed waiting-time distribution is determined by f(), the time distribution of the rate . If f() has a power-law form for low rates, the waiting time-distribution is predicted to have a power-law tail (t)–(3+) (>–3). Distributions f() are constructed from the GOES data. For the entire catalog a power-law index =–0.9±0.1 is found in the time distribution of rates for low rates (<0.1hours –1). For the maximum and minimum phases power-law indices =–0.1±0.5 and =–1.7±0.2, respectively, are observed. Hence, the Poisson theory together with the observed time distributions of the rate predict power-law tails in the waiting-time distributions with indices –2.2±0.1 (1975–2001), –2.9±0.5 (maximum phase) and –1.3±0.2 (minimum phase), consistent with the observations. These results suggest that the flaring rate varies in an intrinsically different way at solar maximum by comparison with solar minimum. The implications of these results for a recent model for flare statistics (Craig, 2001) and more generally for our understanding of the flare process are discussed.  相似文献   

10.
The data of the line series CH3CN 8(K) – 7(K) K = 0 – 7 and line CS J = 3 – 2 were taken simultaneously. At beam size of 16 the emissions of CH3CN and CS have a common center position located near IRc2 with deviations -8 and 5. The observed data show that in Orion KL core the integrated intensities of the two species have double peaks separated by a space of 14. The 2-dimension Gaussian fitting plots (FWHM) are ellipses ofD maj = 26 andD min = 22 for CH3CN 8(K) – 7(K) K = 3 – 6 andDmaj = 39 Dmin = 31 for CS J = 3 – 2 at a distance about 450 pc. Towards the multiple line emission region of CH3CN 8(K) – 7(K) K = 3 – 6, using a simplified very large velocity gradient model to solve the statistical equilibrium and radiative transfer equations, we find to fit the observed results, the optimum physical parameters and kinetic temperatureT k 120 K, densityn(H a) 1.2 × 105 cm–3, velocity gradientV gr 92 km s–1 pc–1 and the local abundance of CH3CNF ab 3 × 10–8. However towards the region of single line emission of CS J = 3 – 2 we have to use LTE and the optical thin approximation on the assumption ofT k= 120 K to obtain the lower limits of column density and then, an averaged abundance of CS of 6 × 10–8.  相似文献   

11.
Intensities and profiles of the H, H, H, K, and D3 lines are measured in a solar prominence. From the profiles of these lines we estimate T = 6400 K and t = 5.7 km s–1. We construct a simple isothermal model which explains the H intensity and profile for an assumed total particle density n T = 3 × 1011 cm–3, and a filling factor, = 1/6.From this model we find that the source function in the H line is nearly constant through the prominence. We estimate from the model that the radiative energy loss at the center of the prominence is of the order of 107 erg s–1 g–1.  相似文献   

12.
Some peculiarities in the behaviour of a model self-gravitating system described by hydrodynamical equations and isothermal equation of state connected with the presence of thermodynamical fluctuations in real systems were investigated in numerical experiment. The values of density and velocity , , respectively, were computed by numerical code perturbed on each time-step and in each computational cell by random values , for modeling such fluctuations. Perturbed values i = i + i ,v i = i + v i were used to initiate the next step of computations. This procedure is equivalent to an introduction into original hydrodynamical equations of Langevin sources which are random functions. It is shown that these small fluctuations (= v =0,2 =v 2 = 10–8) grow many times in marginally-stable state.  相似文献   

13.
We have observed 10 solar bursts during the thermal phase using the Haystack radio telescope at 22 GHz. We show that these high frequency flux observations, when compared with soft X-ray band fluxes, give useful information about the temperature profile in the flare loops. The microwave and X-ray band fluxes provide determinations of the maximum loop temperature, the total emission measure, and the index of the differential emission measure (q(T)/T = cT–1). The special case of an isothermal loop ( = ) has been considered previously by Thomas et al. (1985), and we confirm their diagnostic calculations for the GOES X-ray bands, but find that the flare loops we observed departed significantly from the isothermal regime. Our results ( = 1–3.5) imply that, during the late phases of flares, condensation cooling ( 3.5) competes with radiative cooling ( 1.5). Further, our results appear to be in good agreement with previous deductions from XUV rocket spectra ( 2–3).  相似文献   

14.
On the basis of the solutions obtained in the previous paper, the changes in the scenario of the standard model of the Big Bang are found. The chaos degree (constrainst on fluctuation spectra) is obtained, which could be still preserved by the initially completely chaotic Universe at the time of light elements nucleosynthesist es. The time boundaries of hadron and lepton eras and the time the electron neutrinos and neutrons become frozen in reactions of weak interaction may be shifted up to 1.4 times. The corresponding temperatures may shift off from the standard ones 0.88 times if the mean-square level of fluctuations is close to unity. If the density of the energy of fluctuations concentrated in the short-wave region of the spectrum is less than 1.5 – , the nucleosynthesis leads to a helium abundance coinciding with the observe one. If at the timet es the maximum of the spectral density of the energy is in the long-wave region, that is max ct es the level of the chaos during the period of nucleosynthesis is restricted to 1.76 (where |C K |2 d3 K,C K is Fourier component of the amplitude of metric fluctuations). In particular, the protogalactic vortical disturbances with a wide spectrum 4 × 103 -1( = K/K, = /crit) are compatible with the observed helium abundance.  相似文献   

15.
Vibrational transition probabilities, namely Franck—Condon factors and -centroids have been evaluated by an approximate analytical method for the (A–X), (A–X), and (A–X) system of YO molecule. Morse potential energy curves forX 2+,A 22,A22, andA22, states of YO have been constructed using the latest spectroscopic data. The value of -centroids for the band have been found to decrease linearly with the corresponding wavelengths. We show results for two new transitions of (A–X) and (A–X) and five new bands of (A–X) of YO in the umbral spectrum of the Sun.  相似文献   

16.
On the basis of empirical (D)-dependency at the frequency of 5 GHz constructed using 15 planetary nebulae with the independently measured distances (10–171×10–20 W m–2 Hz–1 ster–1), we evaluated distances of 335 objects. Independent evidence of the correctness of the accepted scale are given. Then(D)-dependency is constructed and it is shown that atD<0.08 pc the mean electron density is higher than the one determined by the Seaton method. We showed that the filling factor diminishes with the increase of the PN diameter (1 atD0.08 pc and 0.2 atD0.4 pc). the ionized mass of 33 PNs is determined. With the diameter increase the ionized mass grows and atD0.4 pc reaches the valueM0.07M . We used the new distance scale when investigating the space distribution of PNs. The mean scale height =130±15 pc and the mean gradient of the change of surface densitym=0.37, which allowed us to estimate the total number of nebulae in the GalaxyN4×104. We divided the PNs according to their velocities (withV LSR>35 km s–1 andV LSR<35 km s–1) and permitted us to confirm that the PN belong to different sub-systems of the Galaxy. The estimated local formation rate of PNs [=(4.6±2.2)×10–12 pc–3 yr–1] is a little higher than the one of the white dwarfs. That can be explained by a large number of PNs having binary cores, which used in our sample. The statistical estimation of PN expansion velocity showed thatV ex increases from 5–7 km s–1 (atD0.03 pc) to 40–50 km s–1 (atD0.8 pc).  相似文献   

17.
At an early stage in the lives of stars and galaxies when they are surrounded by discs, vorticity in the disc concentrates into a central vortex, thus converting a Keplerian velocity fieldu ø r –1/2 into an irrotational velocity fieldu ør –1, which implies inward transfer of angular momentum. Centrifugal forces due to spin-up of the inner region and gravity dominant in the outer region then squeeze gas at intermediate layers, increasing pressure gradient in the axial direction sufficiently to drive a wide-angle low-velocity bipolar outflow from the disc. A logarithmic singularity of vorticity at the axis implies strong centrifugal forces which expand plasma to radiusR where pressure gradient balances centrifugal force density of ions; the much weaker centrifugal force density of electrons cannot balance pressure gradient, so that electrons are driven inwards relative to ions until charge separation limits the relative displacement. Now the radial gradient ofu øcauses ions to rotate at a different rate to electrons, generating an azimuthal current densityj øwhich is the source of an axial magnetic fieldB zin the core of the central vortex. Centrifuging carries lines of B to the core wall, where they are wound into helical force-free configuration with B j. An annular channel of radiusR and thickness R into which parallel helical lines ofj andB are compressed constitutes a magnetic vortex tube (MVT). An MVT separates an inner high-velocity highly collimated outflow from the outer low-velocity wide-angle outflow, and is responsible for jets. Magnetic pinches in the MVT may constrict the core flow at HH objects.  相似文献   

18.
The observations of the reddening of the distant galaxies and the weak diffuse radiation in the clusters of galaxies can be interpreted as a consequence of the presence of dust grains in the intergalactic medium. When allowance is made for the destruction of the grains in collision with particles of the hot gas, its lifetime is about 107–108 yr at a gas concentrationn g 10–3 cm–3. The detection of the infrared (IR) emission from the galaxy clusters might be the test for the proof of the presence of dust grains in the intergalactic medium. In this paper the estimates of the expected intensities and fluxes of IR emission for the spectral region 50–300 are presented for two galaxy clusters in Coma and Perseus. The parameters of the hot gas spatial distribution are chosen from X-ray observations. Having assumed that intergalactic dust can be ejected only from the galaxies, we used such a model for intergalactic dust grains which explains very well the interstellar dust effects. It is shown that the dust temperature, which is determined from the general energetic balance of the dust grains, can achieve some scores of degrees of Kelvin. Two models of the dust spatial distribution are considered. It is found that the maximum of IR flux for the Coma cluster lies near =100 and the same for the Perseus cluster near 50–70. The total fluxes of IR emission from these clusters are about 105–106 Jy and can be detected by modern observational methods.  相似文献   

19.
Data on a statistic derived from the angular covariance function show that (contrary to the claim of Peebles that galaxies are distributed continuously with no distinct scales), superclusters and the maximum size of clusters are probably defined at scales of 15 and 2.0h –1 Mpc. This suggests some stepped-density profile like the idealized models of de Vaucouleurs and Wertz: consideration is therefore given to a semi-continuous hierarchy in which there are galaxies outside clusters, clusters outside superclusters etc. Theories of the origin of clustering by gravitational clumping and the escape of galaxies from clusters suggests the hypothesis that the average mass (m g) of galaxies outside clusters is smaller than that of those inside (=fractionf of the total), a hypothesis supported by results on the continuity of the angular and spatial covariance functions. In a semi-continuous hierarchy, the overall packing fractionf e and the fraction (1-f) of galaxies outside clusters both appear to increase as the distancer from a local origin increases, because a line-of-sight to greater depths intersects systems of the hierarchy of continually greater size (R i). If the hypothesis is valid thatm g inside clusters is slightly larger thanm g outside, the apparent effect is to makem g systematically distance-dependent from a local origin with and 10.3. No direct data on galaxy masses exist to refute such a small trend, but since the absolute magnitudes of galaxies are known to be correlated (very weakly) with their masses, a semi-continuous hierarchy has a location-dependent luminosity function, (M). Within uncertainties as to the steepness of (M) at the bright end, the model is consistent with optical number counts to a limiting photographic magnitudem pg (isotropic slope,q=0.6; semicontinuous modelq=0.64; observation,q=0.67±0.03, standard error.) this removes the discrepancy between the determinations by de Vaucouleurs and Sandageet al. of the thinning factor (1.7). Predictions of the semi-continuous model are made which are at present observationally feasible to carry out. In particular, it is predicted thatq(20<|M|<22)/q(14<|M|<19)2(±0.2).  相似文献   

20.
A study is made of Lyman continuum observations of solar flares, using data obtained by the Harvard College Observatory EUV spectroheliometer on the Apollo Telescope Mount. We find that there are two main types of flare regions: an overall mean flare coincident with the H flare region, and transient Lyman continuum kernels which can be identified with the H and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet Sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density m 5/sx 10–6 g cm–2 in the quiet Sun to m 3/sx 10–4 g cm–2 in the mean flare, and to m 10–3g cm–2 in kernels. From these results we derive the amount of chromospheric material evaporated into the high temperature region, which is found to be - 1015g, in agreement with observations of X-ray emission measures. A comparison is made between kernel observations and the theoretical predictions made by model heating calculations, available in the literature; significant discrepancies are found between observation and current particle-heating models.  相似文献   

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