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1.
. , , .. . . , (, ) .  相似文献   

2.
The exact calculation of scattering and absorption by various sub-micron sized silicate spheres is presented here, using accurately determined optical constants in the wavelength range from 50 m to 0.21 m. The extinction features near 10 m and 20 m for various samples are discussed. It is found that the ratio of peak extinction at 20 m to that at 10 m is constant for small particles up tor=0.4 m, but is less for particles of radius 1 m. The ratio of maximum extinction in the ultraviolet to that at 10 m decreases with increasing particle size.  相似文献   

3.
This paper describes the collection, reduction, and analysis of 0.4–1.0 m Mars imaging spectroscopy data obtained during the 1988 and 1990 oppositions from Mauna Kea Observatory and provides a general outline for the acquisition and analysis of similar imaging spectroscopy data sets. The U.H. 2.24-m Wide Field Grism CCD Spectrograph was used to collect 13 three-dimensional image cubes covering 90% of the planet south of 50°N in the 0.4–0.8 m region (/=245 at 0.6 m) and covering 55% of the planet south of 50°N in the 0.5–1.0 m region (/=293 at 0.75 m). Spectra extracted from these image cubes reveal the detailed character of the martian near-UV to visible spectrum. Images at red wavelengths reveal the classical albedo markings at 100–500 km spatial resolution while images at blue wavelengths show little surface feature contrast and are dominated by condensate clouds/hazes and polar ice. Many of the data acquisition, reduction, and analysis steps discussed here are new or unique to imaging spectroscopy data sets. These techniques exploit the information contained within the spatial domain of data such as these, thus allowing more traditional point-spectral analysis techniques to be expanded into an imaging format.  相似文献   

4.
A spatially homogeneous and isotropic Robertson-Walker model withzero-curvature of the universe is studied within the frame-work of Lyra'smanifold. The gauge-function in Lyra's manifold is taken to betime-dependent. Exact solutions of Einstein equations are obtained for twodifferent early phases of the universe viz. Inflationary phase andradiation-dominated phase by using `gamma-law' equation of statep = ( - 1) . The -index, describing the material content,varies continuously with cosmic time so that in the course of itsevolution, the universe goes through a transition from an inflationaryphase to a radiation-dominated phase. The physical properties of themodels are also discussed.  相似文献   

5.
, 1969–1975 .., 32 . , .  相似文献   

6.
0–2 ( ). . . .  相似文献   

7.
We describe initial results of a program to image massive newly-formed stars with sub-arc second spatial resolution. We discuss high-precision diffraction-limited size measurements at =10 m made using the 3 m Lick telescope. The point-spread function has FWHM 0.7; deconvolution yields a spatial resolution of 0.35. We find that the core component of one such object, LkH 101, is unresolved at these scales, and we are able to set a 95%-confidence upper limit of 270 AU for the diameter of the circumstellar dust shell. This places the dust at the same radial scale as a strong ionized stellar wind region seen at radio wavelengths. Our observations, when combined with published spectral observations, rule out an optically thick circumstellar disk but allow a radially thin, anisotropic distribution of dust, or alternatively an isotropic distribution of dust with a narrow range of large grain sizes.  相似文献   

8.
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   

9.
The results of the observations to search gamma-ray sources with the energy greater than 2×1012 eV, which were made in Crimean Astrophysical Observatory during the years 1969–73 are presented. A technique of the detection of the EAS Cerenkov flashes was used.The quality of the data obtained is analysed. The criteria for the selection of the data free from meteorological variations are considered.It was shown that two objects, namely, Cyg X-3 and Cas -1, may be the sources of high-energy gamma quanta. It is probable that the object with the coordinates =05h15m, =+1° is the source of gamma-rays as well. An unidentified object Cas -1 is variable: gamma-ray flux was observed twice — in Sepember–October 1971 and in December 1972. It is possible that the flux from Cyg X-3 has a period of 4.8 hr.
I I , I I , - >2.1012 . I . I , I I, I ., - -1 Cyg -3- -I . , =0515 ·=+1° -.I -1 I: I J I- - 1971 1972 . Cyg -3, , - T=4.8 .
  相似文献   

10.
. , .  相似文献   

11.
Mt. Wilson numbers of spots data (as defined in Howard et al., 1984) appear to be distributed according to even-odd cycle numbering. Linear fits of annual numbers of spots versus annual sunspot number for even- and odd-numbered cycles have slopes which are statistically different at the 5% level of significance. The existence of an even-odd split in Mt. Wilson numbers of spots data may be due either to a real difference in even- and odd-numbered cycles on the Sun or to a difference in weather at Mt. Wilson (perhaps, related to the 22-yr rhythm of drought in the western United States) during even- and odd-numbered cycles, or both. For cycle 22, an even-numbered cycle, the peak numbers of spots is estimated to be near 2600.  相似文献   

12.
We present high angular resolution (1.2), narrow band (/=0.1) images of the nucleus of NGC253 at three wavelengths in the mid-IR (8.5, 10.0, and 12.5 m). We find that most of the mid-IR flux in the nucleus of NGC253 derives from a very small region 120 pc in diameter. Within this small region there are three spatially and spectrally distinct IR components: two bright compact sources, and a surrounding envelope of low level, diffuse emission. The mid-IR and 6cm radio are loosely correlated in position but not in brightness. The implication is that the mid-IR - radio correlation may begin to break down on small spatial scales relevant to individual star forming regions and large individual sources. These variations in the mid-IR spectra and in the radio-IR correlation imply that the nuclear emission is excited by more than one mechanism and source type.  相似文献   

13.
We present a new diagnostic diagram based on ISOCAMspectra (5-16 m) to distinguish the emission inducedby the active galactic nucleus (AGN) from that associated with thestar formation activity. This diagnostic based on the mid-IRcontinuum and the Unidentified Infrared Band (UIB) intensity allowsus to estimate the relative importance of the three components (HIIregions, diffuse/photo-dissociation regions (PDRs), and AGN) contained ingalaxy mid-infrared emission. In AGN spectra, we confirm the absenceof UIBs presumably photodissociated by the X-UV radiation field. Inaddition, a non-negligible continuum below 9 m commonlyassociated with emission from hot dust is present in AGNs. Adiagnostic diagram derived from these two results can be used fordetecting obscured AGNs embedded in a large concentration of dust.  相似文献   

14.
Evolutionary tracks of 0.9M , 0.7M and 0.6M models for Population II stars have been computed in the post-red giant phase. The stars are initially composed of a helium core containing a mass fraction equal to 0.9 and of a hydrogen-rich envelope. They represent hypothetical remnants of stars after substantial mass loss in previous evolutionary phases or/and at the helium flash.u 0,9M , 0,7M 0,6M . , 90% , . , .Riassunto È stata calcolata per modelli di stelle di 0,9M , 0,7M e 0,6M di Popolazione II l'evoluzione successiva allo stadio di gigante rossa. Inizialmente i modelli constano di un nucleo di elio contenente il 90% della massa totale e di un inviluppo idrogenico. Essi possono interpretarsi come i resti di stelle che abbiano perso una frazione di massa considerevole in fasi evolutive precedenti, o all'innesco violento dell'elio al centro.  相似文献   

15.
We present here the French balloon-borne experiment named AROME. This astronomical instrument is specifically designed for the detection of near infrared emission bands (=3–12m) from extended sources of low surface brightness with an angular resolution of 0.5°. The rms sensitivity achieved is of the order of 10-8 Wm-2sr-1, in terms of the power radiated in the 3.3m band. We recall that this program led to the first detection of the 3.3m feature in the spectrum of the diffuse galactic emission. The scientific results were presented and interpreted in Paper I, Giard et al., 1989. Future work will include both the observation of fainter objects at 3.3m and the detection of other emission bands at 6.2 and 11.3m.  相似文献   

16.
, , , , ,S , , , S Mg. , . , . , ( , ..). B5 B0; (<1%).  相似文献   

17.
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   

18.
Irshell, a mid-infrared echelle spectrograph developed through a collaboration between the University of Texas, the University of California Space Sciences Laboratory, and Hughes Aircraft, has been in regular use for astronomical observations for about five years. It is optimized for high spectral resolution (R10,000) observations of narrow spectral regions (/1/300) and compact sources (a few arcsec), and is sensitive in the 5–25 m region. A wide variety of astronomical objects have been studied. Observing techniques have been developed to achieve maximum sensitivity in those observations for which Irshell is best suited and to allow observations of wide spectral regions and extended objects. We discuss the observing techniques and show some of the data obtained.  相似文献   

19.
The Becklin-Neugebauer objects are identified by means of a wide range of observable features as a separate class of very young and massive stars surrounded by optically thick dust shells. We show that they evolutionarily connect real protostars to compactHii regions. We give criteria which should be appropriate to segregate the BN objects from compactHii regions. Finally, we describe the structure of a typical BN object.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March, 1986.  相似文献   

20.
, . N/E, E r, (E r)=1. , (, ) . .  相似文献   

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