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1.
The deepest survey for H emitting galaxies at z 2.2has recently been made in narrow-band ( 1%) filters around2.1m using SOFI at the ESO NTT telescope. An effective area of 100 sq. arcmin and a comoving volume of 9000 Mpc3 (forH0 = 50, q0 = 0.5) has been covered to a volume weighted 3 line flux limit of 5 × 10-17 erg s-1cm-2. Our survey covered the WFPC2 and STIS fields in the HubbleDeep Field South and an anonymous field about 30 deg. away. Thefaintest limit reached was 3 × 10-17 erg s-1 cm-2 onthe WFPC2 field. In total, 10 convincing candidates with deduced starformation rates in the range 9 - 50 M/yr and an equal number ofmarginal ones have been identified for confirmation and follow-upspectroscopy with ISAAC at the VLT. Based on a very preliminaryanalysis we compare our results with those of earlier surveys andbriefly discuss some possible implications for the form of theevolution out to z 2 and the effects of clustering.  相似文献   

2.
A modeling of the response of the 1549 CIV emission line profile in the spectrum of Seyfert galaxy NGC 5548 to a sharp continuum drop which happened in 1989 is carried out on the basis of observational data taken from the literature. A more rapid response of the red wing of CIV profile suggesting the accretion of CIV-emitting clouds in the broad-line region (BLR) is reproduced. It is shown that the accretion velocity near the central object is consistent with a free fall law whereas at large distances from the center it varies approximately asr –2. The best agreement between observed CIV profile changes and modeled ones is obtained when the mass of the central objectM 1.2 × 108 M . The first approximation of the BLR geometry is also found: the inflow takes place only outside two wide cones with half-opening angle 65° which are disposed like a sand-glass and filled by outflowing material. The angle between the axis of such biconical structure and our line of sight is found to be small ( 9°). It is shown that the outer radius of an accretion disk around the central object does not exceed ~ I light-day (i.e., < 100 Schwarzschild radii), and the outer radius of CIV-emitting BLR is 14 light-days. The nature of a broad blue excess in the CIV profile which did not respond to the continuum change is discussed.  相似文献   

3.
A numerical study has been made of the motion of a compact object consisting of a supermassive black hole with a dense cluster of stars around through a galaxy which has recoiled from the center of the latter as a result of anisotropic emission of gravitational radiation or asymmetrical plasma emission. We find that the effect of dynamical friction on its motion through the galaxy (mass1011 M ) estimated using the impulsive approximation technique, is minimal for an object mass 109 M and for recoil taking place at a velocity larger than that of escape. A velocity 1.1 times the escape velocity is needed for the object to escape from the galaxy, whereas for velocities of recoil less than this critical velocity, damped oscillatory motion ensures. The energy exchange of the object with the galaxy is not large enough to cause appreciable change in the internal energy of the latter.  相似文献   

4.
We present CCD surface photometry of the central region of the bright Seyfert 1 galaxy NGC 4151. The observations were obtained under excellent seeing conditions (0.75 FWHM). Morphological parameters for the bulge of the galaxy are estimated from the observed broad bandV, R, andI surface brightness profiles.From the analysis of the colour maps two distinct nuclear structures emerge perpendicular to each other. One of them is elliptically elongated at PA angle 50°. This direction is close to the direction of the radio jets and coincides with the Extended Narrow Emission Line Region (ENELR). Its extension is about 7 arc sec and its colours are bluer than the surronding bulge. The second structure is smaller in extension (about 1 arc sec) and is elongated at PA130°. Its colours are redder than those of the surrounding bulge. It is suggested that this might constitute areal extension of the Broad Line Region (BLR).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   

5.
An analysis is made of the implications of assuming that suprathermal dust grains (a3×108 cm) of intergalactic origin may acquire cosmic ray energies as high as 1020 eV. These dust grains may attain suprathermal energy (v g3×108 cm s–1) by the Fermi process. Initially the dust grains are accelerated by the radiation pressure against the drag of the ambient gas of the medium, but once these dust grains attain a terminal velocity (U105 cm s–1), then they may be expelled out of the galactic region into the intergalactic medium and finally acquire high energy  相似文献   

6.
Rodríguez Hidalgo  I.  Ruiz Cobo  B.  Collados  M. 《Solar physics》1997,172(1-2):77-83
The inversion of the radiative transfer equation has been applied to a time series of low spatial resolution Ki 7699 Å line spectra, allowing us to obtain a sequence of instantaneous models which are compared to the mean one to derive the 5-min oscillation stratification. The resulting models are reliable from log 0 to log -3.5. The increase of the velocity oscillation amplitude towards higher photospheric layers has been confirmed and quantified. Significant oscillation is observed in temperature.  相似文献   

7.
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   

8.
The physical conditions under which suprathermal grains may loose energy and the processes involving the grains (a3×10–6 cm) destruction are investigated. It is found that the dust grain once attaining the velocityU (105 cm s–1) may attain suprathermal energy (v g3×108 cm s–1) and subsequently may also attain relativistic energy are almost indestructible in the accelerating phase.  相似文献   

9.
On the basis of the Mie theory, the differential cross-section for polarization and the polarization efficiency are calculated for some spherical interstellar grains consisting of ice, silicate, or graphite in the ultraviolet, optical, and near infrared wavelengths. As far as the polarization due to scattering is concerned, these particles scatter light as Rayleigh scattering for 0<x1, wherex is the dimensionless size parameter. The polarization efficienties depend strongly on the value of the imaginary part (m) of the refractive index of grain material whenx1: the efficiency takes a maximum value atx1 and decreases to zero asx approaches zero for the absorbing sphere such as the dielectric particle withm0.1 or the graphite grain in the infrared wavelengths.  相似文献   

10.
A model for second-step electron acceleration in impulsive solar flares is presented. We have extended the theory of stochastic particle acceleration to include Coulomb energy losses which become important at low coronal heights. This inclusion successfully explains the observed steepening of interplanetary electron spectra below 3 MeV following impulsive solar flares taking place at low coronal heights. It also explains the observed spectral differences of relativistic electrons in long-duration and impulsive flares.  相似文献   

11.
On the basis of recent new information on regular and chaotic magnetic fields in coronae of spiral galaxies, we discuss propagation of ultra-high energy cosmic rays of energies exceeding 1017 eV in the galactic corona. It is shown that the expected regular magnetic field is able to confine to the corona protons of energies up to 3×1019 eV. Chaotic magnetic fields of the corona play an important role in dynamics of cosmic-ray protons of energy up to 7×1018 eV.  相似文献   

12.
From 59 spectra collected at Asiago from 1969 to 1976, we obtain the spectroscopic orbit of the binary V 505 Mon. The rather long periodP=53.7805 days and semiamplitudeK 1=83±4 km s–1 of the primary component imply a fairly large mass of the secondary (m 23.2±0.4m ). Apparently also lines of this latter have been recorded, thus indicating highly massive components (m 150,R 1=26,m 227,R 2=14, in solar units) in a detached system (separation 255R ). The already reported variation of 0.15 mag., with period about one day, together with H emission, we detected, point toward a possible massive X-ray progenitor.  相似文献   

13.
The probable connection between cosmic rays and the electromagnetic state of the interplanetary medium was recognized by Hannes Alfvén as early as 1949 (Alfvén, 1949, 1950); he pointed out that the properties of cosmic rays necessitate a mechanism, external to Earth but within the solar system, capable of accelerating particles to extremely high energies. In advocating the view of local origin for part of the cosmic-ray spectrum, Alfvén and his colleagues developed a very general type of acceleration mechanism called magnetic pumping. The unique data set of the two Voyagers extends over an entire decade (1977–1987) and is most suitable to explore the problem of acceleration of charged particles in the heliosphere. The energy coverage of the Low Energy Charged Particle (LECP) experiment covers the range 30 keV to several hundred MeV for ions and 22 keV to several MeV for electrons. Selected observations of interplanetary acceleration events from 1 to 25 AU are presented and reviewed. These show frequent acceleration of ions to several tens of MeV in association with shocks; highest energies (220 MeV oxygen) were measured in the near-perpendicular ( Bn 87.5°) shock of January 5, 1978 at 1.9 AU, where electron acceleration was also observed. Examples of ion acceleration in association with corotating interaction regions are presented and discussed. It is shown that shock structures have profound effects on high-energy (70 MeV) cosmic rays, especially during solar minimum, when a negative latitudinal gradient was observed after early 1985 at all energies from 70 MeV down to 30 keV. By early 1987, most shock acceleration activity in the outer heliosphere (25 to 30 AU) had ceased both in the ecliptic (Voyager-2) and at higher (30°) ecliptic latitudes (Voyager-1). The totality of observations demonstrate that local acceleration to a few hundred MeV, and as high as a few GeV is continually present throughout the heliosphere. It should be noted that in 1954 when Alfvén suggested local acceleration and containment of cosmic rays within the solar system, no one treated his suggestion seriously, at any energy. The observations reviewed in this paper illustrate once more Alfvén's remarkable prescience and demonstrate how unwise it is to dismiss his ideas.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.  相似文献   

14.
On November 27, 1974, a map of the Moon was obtained at 6 cm wavelength with the 100-m-telescope in Effelsberg. The high angular and favourable temperature resolution allowed an interpretation of the observed brightness distribution. The dominant feature of the brightness distribution is the centre-to-limb variation, particularly noticeable in the direction of the poles. The exponent of the commonly adopted cos ()-law, describing the temperature variation across the lunar disk, is determined as 0.4. The North-South variation of the lunar surface temperature is estimated to be 30%; the depth of penetration (L e) of electromagnetic waves of 6 cm wavelength is found to beL e 17 m.  相似文献   

15.
The observed energy spectra in synchrotron sources are power laws,N (E)=KE –, with the distribution in peaked around 2.5. These are consistent with initially injected spectra with between 1 and 2, subsequently steepened by synchrotron losses. Contrary to the results of Kardashev (1962), it is shown that statistical acceleration when coupled with synchrotron losses lead naturally to the formation of flat stationary spectra with 1. These stationary spectra have bends near the energy at which synchrotron losses balance the energy gains by acceleration. Above this bend the spectrum tends to =2. The time evolution of an initial spectrum towards the stationary spectrum is investigated. It is suggested that the initially flat spectra with 1 to 1.5 observed in some variable sources result from an incomplete approach to the stationary spectrum, and that in sources with constant acceleration spectra with 2 are to be expected.  相似文献   

16.
A map of the Moon at 2 cm wavelength is presented. The angular ( 1arc) and temperature resolution (< 0.1 K) is sufficient to study systematic details of the brightness distribution. In particular, the centre-to-limb variation is considered. An estimate of the dielectric constant is possible (1.4 2.5). The existence of a temperature gradient in the lunar surface layers is used to derive the depth of penetration of electromagnetic waves (L e ), which isL e 8 m for 2 cm wavelength. The parameters derived from the 2 cm map are found to be compatible with those obtained from a former observation at 6 cm wavelength.  相似文献   

17.
Within the framework of a Gamow cosmology with massive neutrinos a scenario is proposed in which both galactic halos and globular clusters are formed due to the existence of a critical injection mass. Galactic halos are formed at red shift z10–100 by self-gravitating neutrinos, and globular clusters atz103 by a critical injection mass of primordial plasma (Gamow's Ylem).  相似文献   

18.
Cold plus hot (neutrino) dark matter models are studied and compared with the tilted cold dark matter models (which have a non-Zel'dovich initial density perturbation spectrum). For the hybrid dark matter models, a simpler treatment for the relativistic neutrinos is presented. The numerical results of this treatment are shown to be in good agreement with those given by other authors. Comparing the theoretical and the observational results of the quadrupole fluctuations of the cosmic background radiation and the large-scale velocity field of galaxies, the hybrid dark matter models require a fraction of neutrino density 0.3, a fraction of cold dark matter c 0.7 and a number of massive neutrino speciesN = 1 for the case of Hubble's constantH 0 = 50 km s–1 Mpc–1. The distribution of comoving number density of quasars at high redshifts is studied using the Press-Schechter theory. The calculations show that the hybrid dark matter model ( c 0.7, 0.3) and the tilted CDM model withn = 0.7 0.8 both account for the observed quasar abundance at high redshift.  相似文献   

19.
Julius Feit 《Solar physics》1971,17(2):473-490
An analysis of solar flare data indicates that the graph of log(nt 3/(2–)) deviates late in the solar event from the straight line predicted for the infinite, unbounded interplanetary medium. It is shown by mathematical analysis, utilizing a model based on the radial diffusion coefficient D = Mr , with 1, that the deviation can be ascribed to the loss of flare particles through an external boundary at about 5–6 AU from the Sun. An inner region terminating at 5–6 AU, followed by an extensive region of increasingly less resistance to the diffusion of flare particles is also feasible and it is shown that measurements taken at the Earth cannot predict the extent of this outer region. The results are applicable to either the isotropic or highly anisotropic models. The constant diffusion model is shown to be inadequate since it requires a boundary 1.5 AU from the Sun. In view of the present and previous studies of solar flare data, it is asserted that the fundamental principle governing the diffusion of solar flare particles through interplanetary space is the radial diffusion coefficient mode of propagation.  相似文献   

20.
A semi-continuous hierarchy, (i.e., one in which there are galaxies outside clusters, clusters outside superclusters etc.), is examined using an expression of the field equations of general relativity in a form due to Podurets, Misner and Sharp. It is shown (a) that for a sufficiently populous hierarchy, the thinning factor( i+1/ i [r i /r i+1] is approximately equal to the exponentN in a continuous density law (=aR –N) provided (r i /r i+1)3-1; (b) that a hierarchical Universe will not look decidedly asymmetric to an observer like a human being because such salient observers live close to the densest elements of the hierarchy (viz stars), the probability of the Universe looking spherically symmetric (dipole anisotropy0.1 to such an observer being of order unity; (c) the existence of a semi-continuous or continuous hierarchy (Peebles) requires that 2 if galaxies, not presently bound to clusters were once members of such systems; (d) there are now in existence no less than ten arguments for believing 2, though recent number counts by Sandageet al. seem to be in contradiction to such a value; (e) Hubble's law, withH independent of distance, can be proved approximately in a relativistic hierarchy provided (i)N=2, (ii)2GM(R)/c 2 R1; (iii)Rc (iv)M0 in a system of massM, sizeR (f) Hubble's law holds also in a hierarchy with density jumps; (g)H100 km s–1 Mpc–1; (h) objects forming the stellar level of the hierarchy (in a cosmology of the Wilson type) must once have had 2GM/c 2 R1; (i) there is a finite pressurep=2Ga in all astrophysical systems (a=R N ,N2); (j) for the Galaxy, theory predictsp G7×10–12 dyn cm–2, observation givesp G5×10–12 dyn cm–2; (k) if the mass-defect (or excess binding energy) hypothesis is taken as a postulate, all non-collapsed astrophysical systems must be non-static, and any non-static, p0 systems must in any case be losing mass; (1) the predicted mass-loss rate from the Sun is 1012 g s–1, compared to 1011 g s–1 in the observed solar wind; (m) the mass-loss rates known by observation imply timescales of 5×109 years for the Sun and 1010 years for other astrophysical systems; (n) degenerate superdense objects composed of fermions must haveN-2 if they were ever at their Schwarzschild radii and comprised a finite numberN B of baryons; (o)N B1057N for degenerate fermion and boson systems; (p)285-4; (q) the metric coefficients for superdense bodies give equations of motion that imply equal maximum luminosities for all evolving superdense bodies (L max1059 erg s–1); (r) larger bodies have longer time-scales of energy radiation atL max (10–5 s for stars,1 h for QSO's) (s) expansion velocities are c soon after the initial loss of equilibrium in a superdense object; (t) if the density parametera(t) in aR –N isa=a (non-atomic constants of physicsc, G, A), andA, thenN=2; (u) N2 is necessary to giveMM at the stellar level of the hierarchy;(v) systems larger than, and including, galaxies must have formed by clumping of smaller systems and not (as advocated by Wertz and others) in a multiple big bang.  相似文献   

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