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.
The radio maps of ten small Hii regions at λλ=2.8, 6 and 11 cm, obtained with the 100-m MPIR radiotelescope, are given. A comparison of the radio fluxes obtained with parameters of exciting stars is carried out. For four compact Hii regions — namely, S146, S152, S237 and S297 — we present the results of observations with the radiotelescope of the U.S.S.R. Academy of Sciences, RATAN-600. The paper also presents estimates of the physical conditions in nebulae, and conclusions are drawn about the possible stage of their evolution.  相似文献   

2.
The Hii regions S254, 255 and 257 in the constellation of Orion are close together on the sky and appear like a triple object. Fabry-Pérot radial velocities of the Hii regions as well asUBV photo-electric magnitudes of their exciting stars are obtained. The data show that (1) all three nebulae are at a distance of 2.5 kpc; (2) an excess extinction is observed in S255 and S257 while S254 shows no excess extinction; (3) S255, identified as an IR and a molecular source, is the youngest object of the group. It is concluded that the three Hii regions are at different evolutionary stages.  相似文献   

3.
We have calculated for extragalactic Hii regions, the expected relationship between the radio flux at 11 cm and the infrared flux at 11 and 20 m based on the grain models and the parameters which fit the observations of galactic Hii regions. It is shown that the measured infrared fluxes of extragalactic Hii regions are consistent with the expected infrared fluxes for these objects.  相似文献   

4.
We report on extensive spectroscopic observations of the WR-ring nebulae NGC 2359 and RCW 78, respectively, excited by the WN5 stars HD 56925 and WN8 HD 117688. For the first object we have determined abundances for O/H, Ne/H, N/H, and He/H in many different positions, including the ionized gas in the bubble, inside the optical shell structure, and the outermost zones associated with the S 298 Hii region. We do not find any significant difference in the N/H and O/H abundances over the entire nebula. The O/H and N/H abundances expected are close to those for a normal Hii region located at similar distance. In the case of He/H we find indication of local enhancements which sum to the abundance of metal rich galactic Hii regions like M17. RCW 78 appears to show slight overabundances of He/H and N/H in the two observed positions.The ionising temperature for the WN central star (HD 56925) of NGC 2359 is determined from the observed Hii region spectrum giving a value of 50000 K, appropriate to its spectral type.  相似文献   

5.
Preliminary results of a programme aimed at investigating the presence of Hii regions around Seyfert nuclei are presented. We have detected extended zones of ionized gas around some classical Seyfert galaxies. We think that the ionizing mechanism in these extended regions is UV radiation from young stars formed in a recent burst of star formation. In many instances the objects studied show morphological disturbances arising from the interaction with nearby companion galaxies.  相似文献   

6.
In the preceding paper by Vengeret al. (1984) the results of observations of neutral gas in the vicinity of some galacticHii regions were considered; and it was demonstrated that 17 of the regions observed are surrounded by expandingHi envelopes. This paper describes a model of interaction between theHii regions and the surrounding interstellar medium constructed on the basis of the said results. It is assumed that the main dynamic factor in the envelope formation mechanism is the total stellar wind from the stars which ionze theHii regions. The employment of the observations of the line at =21 cm, of the radio continuum and IR dust continuum made it possible to determine the differential mass spectra of the stars exciting theHii zones and calculate some characteristics of the stellar population. The mass spectrum index of the objects considered turned out to be much higher than that for the mass spectra of background stars and scattered clusters of stars.  相似文献   

7.
We examined the radial distribution of 1227 blue knots in the rectified planes of 32 galaxies and showed that the method is equivalent to mapping the distribution ofHIi regions from narrow-band imaging in H. The blue knots show less detail in their distribution, as compared with Hii regions or with a parameter measuring the local efficiency of star formation. This is interpreted as showing the diffusion of OB stars out of the regions where they formed.  相似文献   

8.
Thirty four objects appearing in the SharplessCatalogue of H ii Regions with radio flux densities below 0.1 fu* at 1400 MHz, are studied. It is shown that two of them are planetary nebulae, two are reflection nebulae and two weak emission-reflection nebulae. From statistical arguments it is concluded that six may be evolved planetaries while the remaining are faint nearby Hii regions excited by stars of relatively advanced spectral type.  相似文献   

9.
The Monoceros ring, a circular optical nebulosity 3°.5 in diameter and centred at R.A.=6h37m, Dec.=6°30 (l ii =205°.5,b ii =0°.2) is in good structural agreement with radio observations. A neutral hydrogen shell is also accurately projected on the ring. These observations are consistent with the Monoceros ring being a supernova remnant 90–100 pc in diameter expanding at about 45 km s–1 and having an age of the order of a million years. Bright Hii regions containing early-type stars (e.g., galactic cluster NGC 2244 in the Rosette nebula) and extremely young stars of the OB association Mon OB2 lie at the edges of the ring. The positional and temporal coincidence of the Mon OB2 association with a supernova remnant suggests that probably the star formation in this region is induced or speeded up by the passage of a supernova shock wave through the clumpy interstellar medium.  相似文献   

10.
The radio spectra of the Rosette Nebula, the source S280 and the Monoceros Nebulosity are established over a wide range of frequencies. The radio spectra of the Rosette Nebula and S280, show a typical thermal shape. Physical parameters of both Hii regions are derived by adopting a spherical model.The radio spectrum of the Monoceros Nebulosity shows a non-thermal shape (sp. index –0.66) but the exact nature of the object is not clear. Assuming it is an SNR some of its physical characteristics are estimated.  相似文献   

11.
A detailed analysis of the multiplet structure of lines used for observations of stellar magnetic fields is presented. It is shown that LS-coupling does not hold good for many of the spectroscopic terms of Tiii and Crii and that the magnetic fields observed in several magnetic stars are strong enough to produce transition to the Paschen-Back effect in some of these lines. In order to avoid possible erroneous results it is recommended that only lines originating from Russell-Saunders terms be used for magnetic observations. A list of Tiii, Crii and Fei lines is given which should not be used in measuring strong magnetic fields in magnetic stars.  相似文献   

12.
We have studied the interstellar column densities of Alii, Siii,Sii, Feii, Niii, and Znii in the direction of 18 O- and 6 B-type stars so as to improve the relations of element depletions withE(B-V), and to look for other possible relations with two stellar parameters: namely, the rate of mass loss and rotational velocity. The stars were chosen in order to cover several directions in the Galaxy, as well as a wide range in interstellar reddening. We found a clear inverse trend relating the abundance of elements to interstellar reddening.  相似文献   

13.
A calibration previously determined for the evolution of the equivalent width of the emission line H with age for Hii regions (Dottori, 1981) is applied to detached extragalactic Hii regions. The frequency distribution of ages seems to indicate that some of these regions had other bursts of star formation so important as the observed last one.  相似文献   

14.
A detailed photometric comparison between a Mgii K filterheliogram and a nearly simultaneous Caii K spectroheliogram is presented. The comparison shows a close correspondence in both location and intensity of the bright features on the Sun with a correlation coefficient of 0.92 ± 0.02 between the Mgii and the Caii intensities in active regions.A small flare is most likely observed in the Mgii heliogram giving a substantial contribution to the recorded intensity.We also estimate theoretically the heights in the solar atmosphere at which the Mgii K and Caii K lines are formed. Taking into account the general shape of the line profiles and the different passbands used in the recordings we arrive at an average height of formation of 1700–1900 km above the photosphere for these particular heliograms.  相似文献   

15.
A model of the chromosphere and transition zone for quiet regions of the Sun is given.The height dependence of temperature and density are different for the borders of the supergranules and for their inner parts. The difference is caused by the enhanced mechanical energy flux at the places of strengthened magnetic field.The average dependence of density on height is given by eclipse data, the corresponding values for temperatures are obtained by a trial and error method using calculation of solar radio emission for different wavelengths and comparison with observations.The adopted model is consistent with observational data on the solar visual, radio and UV emission. This model also accounts for the brightness distribution on spectroheliograms taken in H wings, K232 Caii and in several UV spectral lines.  相似文献   

16.
Measures of line intensities from high-dispersion spectrograms of HD 92207, 100262, 125835 and 161912 are presented. Analysis with a theoretical curve of growth leads to the selection of parameters for excitation temperature and microturbulence. The turbulent velocity in the atmosphere of HD 92207 varies through a factor of two in approximately one month, in phase with a similar change in the equivalent width of H. The spectra of the other three stars do not appear to vary, but the turbulent velocity is much less for Fei than for Feii and Crii.  相似文献   

17.
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   

18.
The results of a systematic radial velocity survey of two Hii regions in the Cygnus-X complex are presented. The [Nii] emission line components obtained at many positions over each object have been compared and correlated with other phenomena. It is suggested that they are probably connected objects and may be part of a giant shell or cylinder.  相似文献   

19.
Among manganese stars, Herculis is of great interest because of the unusual strength of the scandium lines. We present intensity measurements for numerous lines ofCii, Mgi, Mgii, Siii, Caii, Scii, Tiii, Crii, Mni, Mnii, Fei, Feii, Coii, Srii,Yii, and Zrii.  相似文献   

20.
A classification of the observational data on NGC 2264 is presented. Optical, infrared and radio data for the Hii region are tabulated, and maps of the molecular cloud structure are shown. The observations of the NGC 2264 star cluster are also summarized. The role of star formation in this young region is briefly assessed.  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