首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
From spectroscopic observations of the emission lines H, 4959 and 5007[Oiii], H, 6584[Nii], 6717 and 6731[Sii] and some interferometric data in H and [Nii] it was established that NGC 6164 and NGC 6165 have characteristics of normal Hii regions for Ne and Te. They are embedded in a very tenuous medium nearly coincident with the Strömgren sphere of the central star HD 148937, corresponding to the outer peripheral structure described by Westerlund. Variations of the relative abundances of N, O, and S are discussed.  相似文献   

2.
CCD narrow band imagery of the southern barred spiral NGC 613 has been obtained in the light of H, H, [Oiii] 5007 Å, [Oii] (3726+29) Å and continua at 3765, 5230, and 6500 Å. Absolute fluxes have been obtained for the lines H and [Oiii] 5007 Å and continua at 5230 and 6500 Å. Distribution of ages, monochromatic colour vs absolute brightness and [Oiii]/H are discussed.  相似文献   

3.
Sommaire Les photographies monochromatiques en H, [Nii] 6584 et [Oiii] 5007 ont été obtenues sur NGC 281, IC 434 et M 16 eu vue de la détection et de l'étude des bords brillants. A partir de ces photos, on accède à la carte d'égal rapport [Nii]/H grâce à la méthode décrite par Louise et Sapin (1972). A l'exclusion des bords brillants, ce rapport varie très peu à l'intérieur d'une même nébuleuse. Par contre à l'approche des fronts d'ionisation, il augmente de façon spectaculaire et systématique.Le renforcement de la raie [Oiii] vers les bords brillants suggère la présence des inhomogénéités (globules ou/et filaments) et le rôle possible que jouent les mécanismes d'échange de charges étudiés par Aller et Keyes (1980).
Observations of bright rims in NGC 281, IC 434 and M 16
Monochromatic plates are obtained in H, [Nii] 6584 and [Oiii] 5007 lines for three Hii regions: NGC 281, IC 434 and M 16. They allow both detection and physical studies of bright rims. Indeed, it is shown that bright rims appear most contrasted on [Nii] and [Oiii] plates. Furthermore, maps of ratio [Nii]/H are derived from the method described by Louise and Sapin (1972). This ratio remains practically constant within the nebula, except for bright rims where it increases. This may be understood by means of both increasing abundanceN(N+/N(H+) and temperature following to the model of Mallik (1975).The [Oiii] enhancement towards bright rims in M 16 suggests the presence of inhomogeneities (globules or/and filaments) and the possible role played by charge exchange mechanisms as pointed out by Aller and Keyes (1980).
  相似文献   

4.
Narrow band-pass direct photographs have been secured of the central region of 30 Doradus and of several other nebulosities in the Magellanic Clouds. We have utilized an image tube camera attached to the Yale one-meter telescope at the Cerro Tololo Interamerican Observatory. Interference filters whose band passes were selected to allow for the radial velocities of the Magellanic Clouds have been utilized to record monochromatic images of [Nii] 6584, H, Hei 5876, and [Oiii] 5007. In 30 Doradus the main filamentary structures appear to be very similar in H, Hei, [Nii], and [Oiii] at least in the inner regions where most spectroscopic measurements have been made. The features appear to be material bounded rather than radiation bounded and the excitation differences are very small. Likewise, in NGC 346 in the Small Magellanic Cloud the [Oiii] and H images are very similar, but in N44 in the Large Magellanic Cloud excitation differences do appear. The implications of these observations for chemical compositions of nebulosities in the Magellanic Clouds would appear to be that spectroscopic and scanner studies should be supplemented by monochromatic photographs. Some nebulosities can be handled by simple models while for others excitation differences must be taken into account.Guest investigators at Cerro Tololo Interamerican Observatory operated by the Association of Universities for Research in Astronomy under contract with the National Science Foundation  相似文献   

5.
Monochromatic images in H, H, [Nii] 6584, [Sii] 6717, and [Oiii] 5007 lines are presented for a morphological study of planetary nebulae. Narrow bandpass (=5 to 10Å) interference filters are generally used in order to discriminate peculiar structures existing in different emission lines. However, large bandwidths (=50 Å) along with long exposures, are also necessary in searching for faint nebulosities associated with planetaries.Three faint objects of the Abell's list of old planetary nebulae have been observed through narrow band filters, by means of an image tube (A33, A36 in Chile) or the image photon counting device (A79 at the Haute Provence Observatory). Following the H/[Nii] intensity ratio, a discussion is given about the distance previously derived with some assumptions concerning the measured red fluxes.  相似文献   

6.
In the field partsH, K, L andM of the Orion Nebula, indicated in Figure 2, no obvious differences do appear in the monochromatic photographs obtained in H+[Nii], [Oii], the visual continuum and the range of the Balmer continuum. A different situation we meet in the rest of the field, where one observes two types of featuresA andB, distinguished in Figure 1 by solid and dashed bordering lines respectively. Relative to the conditions in the H+[Nii] pictures, the typeA areas gain in intensity in the photographs taken in the visual continuum. the emission in the forbidden [Oii] lines at 3727 Å is correlated with H+[Nii], the emission in the range of the Balmer continuum with the visual continuum. According to these properties theA-areas must have a particularly high percentage of scattered star light.Most of the areas with identical monochromatic features show a high deficiency of cluster stars correlated with a low surface brightnesss and a reduced gas density. This is explained by an opaqueness of the emission strata in the direction in the line of sight and a position of the same nearer to the observer than the extension of the cluster. There appear surface structures at large distances from the Trapezium which show a correlation between the intensity of scattered star light and the intensity of the emission of the higher ions ([Oiii], [Neiii]). This observation is considered as a proof that canals through the nebular cloud complex allow in some directions the exciting radiation to reach large distances from the star without having suffered an appreciable absorption or scattering.  相似文献   

7.
Areas of network emission features in C ii 1135, C iii 977, O iv 544 and O vi 1032 were measured in and out of coronal holes. In the quiet Sun these areas, on the average, showed a 20% increase between C ii and O vi. In the coronal holes there was no significant average variation, but a number of the features showed an interesting decrease in area at intermediate temperatures.  相似文献   

8.
A detailed list and analysis of line identifications of five UV spectra of the RS CVn-type binary system TY Pyxidis are presented. These spectra are recorded at different phases with the International Ultraviolet Explorer (IUE). Two of them are in the wavelength range1235–1950 Å while the other three in the range2700–3110 Å.The far-UV spectrum of TY Pyx is mainly an emission spectrum dominated by the emission lines of the ions:Ci, Oi, Cii, Siii, Heii, Alii, and Feiii. We also pointed out the existence of a Feiii [34] line in absorption.The UV spectrum between 2700–3110 Å is dominated by weak absorption lines. Two satellite components are indicated for many lines, which correspond to the two stars of the system, in the two out of the three spectra (LWP 13386 and LWP 13347).Violet emission wings are observed for Fei [1], Tii [1],Oiv [1], and Siiii [1]. The UV spectrum of TY Pyx is also characterized by the multi-structure of Mgii [1] resonance lines.Based on data from the International Ultraviolet Explorer, de-archived from the Villafranca Data Archive of the European Space Agency.  相似文献   

9.
The ionized gas in NGC 5236 was studied by spectroscopic means. The radial behaviour of the line ratios [Nii]/[Sii], H/[Sii] suggest a real nitrogen overabundance in the central regions of that galaxy.  相似文献   

10.
Three southern planetary nebulae (NGC 2818, He 2-130, and NGC 3132) have been observed with the IDS (Image Dessector Scanner) combined with the Boller and Chivens spectrograph mounted at the Cassegrain focus of the 1.52 m telescope of the ESO in Chile. The spectrograph dispersion was 60 Å mm–1 in the spectral range 6170–7298 Å. The slit aperture was 4×4. Spectra were obtained from an array of positions across each nebula along the E-W direction and/or N-S direction. The data reduction followed the standard IHAP routines for IDS observations. In order to derive electron density, only the [Sii] lines (6617 Å–6731 Å) are given in this paper. The results are in agreement with a shell structure for the observed nebulae.

Toutes les observations ont été faites à l'Observatoire européen Austral (ESO) au Chili.  相似文献   

11.
The absolute limb effect is presented for Fei lines 3767 and 3969; for five Tii lines of multiplet 42 near 4535 and one Tiii line at 4534; two lines of Mgi, 4571 and 5172; two lines of Baii at 5854 and 6497. The scattered light of the McMath solar telescope is illustrated by several figures but not applied to the limb-effect observations. It is suggested that the supergravity shift at the limb is the result of scattering of the atoms in anisotropic velocity field.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.  相似文献   

12.
Quiescent prominences It is found that Heii 4686 is emitted in the same cold region of 10000 K as hydrogen, metal and neutral helium emission lines. This conclusion is based on the finding that the observed width of 4686 is the same as the calculated width of 4686. The calculated width is derived from the observed widths of hydrogen and metallic lines. The large intensity of Heii 4686 in 10000 K can be explained by the ionization of Heii due to the UV radiation below 228 Å that comes from the corona and the transition region.Loop prominences The very broad width (30 to 50 km s–1) of 4686 for two post-flare loop prominences shows that the Heii line is emitted in hot regions different from regions of hydrogen and metal emission. From the widths of the Balmer lines and many metallic lines the kinetic temperature for one loop is found to be 16000 K in one part and 7600 K in another part. The electron densities are 1012.0 cm–3 and less than 1011.0 cm–3 respectively.Chromosphere The intensity of 4686 in the chromosphere can be interpreted in terms of a temperature of 10000 K with the ionization due to UV radiation. But, since observations of the width of 4686 are not available, a definitive conclusion for the chromosphere cannot be reached.  相似文献   

13.
The line profiles of L, Ca ii K and Mg iik were measured with the spectrometer of the Laboratoire de Physique Stellaire et Planétaire on board of OSO-8. The results of these measurements are presented.Mitteilungen aus dem Kiepenheuer-Institut Nr. 181.  相似文献   

14.
Taking into account the effect of roughness (or local departures from sphericity) of the emitting layers in the chromosphere-corona transition zone (CCT) allows one to determine the optical depths of layers responsible for resolved structures in Cii, Ciii, Oiv, and Ovi lines. The result, at the top of the irregularities, is of the order of respectively 1 3.5,2.0, 1.6,0.5, and for the bottom of these irregularities, 2 = 0.7, 0.4, 0.3, 0.25. The characteristic angle of these irregularities is, respectively, of the order of 35 °, 33 °, 35 °, and 41 °. For unresolved structures of Civ and Ovi (already analyzed in the spherical symmetry hypothesis in Paper III), one finds 1 0.6; 0.9 and 2 0.12; 0.2 in the case of quiet areas; in the case of active areas, the range is broader for Civ and Ovi, from 1.0 to 1.7 for 1 and from 0.2 to 0.9 for 2. The values obtained from Ovi are in reasonable agreement with each other for resolved and unresolved structures. And the obtained values of 1 and 2 correspond not too badly with the determinations made in Paper III, by methods not exceedingly influenced by the spherical symmetry hypothesis.  相似文献   

15.
High resolution spectrographic observations of 220 nearby galaxies with bright nuclei have been made mainly at H and [Oiii] 5007 to search for signs of nuclear activity. In many cases evidence for weak activity has been found.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

16.
A photoelectric Fabry-Pérot spectrometer is used to record the line profiles of H and [Nii] at 22 points in the nebula. The ratio of intensity H/[Nii] is used to derive an electron temperature distribution with values between 5700° and 9100° showing a peak at the centre of density. These temperatures are compared with the H Doppler temperatures to estimate excess velocities of mass motion. Together with the shifts of the H line centres, these lead to an evaluation of the velocity field in the nebula.It is suggested that the nebula consists of a core expanding at about ±10 km/sec–1 surrounded by a thick peripheral shell in which large scale mass motions are small. Non-thermal broadening suggesting turbulent velocities at about the speed of sound is observed in this shell and is attributed to small scale dynamic effects in a non-smooth density distribution. The effect of such expanding cores on heliocentric velocities of galacticHii regions is discussed.  相似文献   

17.
Introduction of the O+++H0O++H+ charge exchange rate suggested by Butler, Bender and Dalgarno leads to theoretical nebular models that differ from those previously computed in several important respects. Different elemental abundances, bluer central star energy distributions, and truncated (material limited) models are required. If the argon abundance is fixed from the 7135 [Ariii] line intensity, 4740 [Ariv] is invariably predicted to be much too strong. Better atomic parameters, together with improved charge exchange rates for other ions, and more accurate dielectronic recombination rates may alleviate the situation.  相似文献   

18.
High spatial resolution spectral observations of five hedgerow prominences were made in H, He i D3 and Ca ii H and K.The observed relations between the lines were not the same in all prominences. The Ca ii H and K lines were 2–4 times brighter relative to H and D3 than predicted theoretically. The optical thickness of H was less than for the H and K lines, the H was optically thin in medium faint prominence structures. Faint structures appeared slightly hotter than bright structures.On leave from Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, Oslo 3, Norway.  相似文献   

19.
The suspected symbiotic nature of MH80-5=AS 360 was confirmed for the first time by spectra taken in 1967 at Asiago Observatory (Marini, 1969) showing the [Oiii] and [Neiii] forbidden lines, together with strong Heii lines and TiO bands. According to Allen (1984) nebular lines were absent in 1978, while we recorded them again in 1985. Further excitation strengthening up to [Fevii] andOvi, in 1990 were noted by Munari and Buson (1991). The evolution implies density variability in the thick nebula surrounding this new variable system.  相似文献   

20.
Ø. Hauge  H. Sørli 《Solar physics》1973,30(2):301-308
Two new Th ii lines have been identified in the spectrum of the solar photosphere. The abundance derived from these lines together with the previously known Th ii line at 4019 Å, is log Th = 0.85 ± 0.20 in the log H = 12.00 scale. Analysis of three Pb i lines in the photospheric spectrum resulted in an abundance of log pb = 1.90 ± 0.10. The solar Th/Pb ratio is: Th/ Pb = 0.09 -0.005 0.09 .  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号