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Astronomy Reports - Several errors were found in this paper, which however did not influence its main conclusions. In Table 2 of Section 2, the references for the data in columns (6)–(9) and... 相似文献
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The 20-cm radio continuum fluxes of 91 HII regions in a previously compiled catalog have been determined. The spectral types of the ionizing stars in 42 regions with known distances are estimated. These spectral types range from B0.5 to O7, corresponding to effective temperatures of 29 000–37 000 K. The dependences of the infrared (IR) fluxes at 8, 24, and 160 μm on the 20-cm flux are considered. The IR fluxes are used as a diagnostic of heating of the matter, and the radio fluxes as measurements of the number of ionizing photons. It is established that the IR fluxes grow approximately linearly with the radio flux. This growth of the IR fluxes probably indicates a growth of the mass of heated material in the envelope surrounding the HII region with increasing effective temperature of the star. 相似文献
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A. P. Topchieva D. S. Wiebe M. S. Kirsanova V. V. Krushinskii 《Astronomy Reports》2017,61(12):1015-1030
A search for infrared ring nebulae associated with regions of ionized hydrogen has been carried out. The New GPS Very Large Array survey at 20 cm forms the basis of the search, together with observations obtained with the Spitzer Space Telescope at 8 and 24 μm and the Herschel Space Telescope at 70 μm. Objects having ring-like morphologies at 8 μm and displaying extended emission at 20 cm were selected visually. Emission at 24 μm having the form of an inner ring or central peak is also observed in the selected objects. A catalog of 99 ring nebulae whose shapes at 8 and 70 μm are well approximated by ellipses has been compiled. The catalog contains 32 objects whose shapes are close to circular (eccentricities of the fitted ellipses at 8 μm no greater than 0.6, angular radius exceeding 20″). These objects are promising for comparisons with the results of one-dimensional hydrodynamical simulations of expanding regions of ionized hydrogen. 相似文献
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Total infrared fluxes are estimated for 99 HII regions around massive stars. The following wavebands have been used for the analysis: 8 and 24 μm, based on data from the Spitzer Space Telescope(IRAC and MIPS, respectively); 70, 160, 250, 350 and 500 μm, based on data from the Herschel Space Observatory(PACS and SPIRE). The estimated fluxes are used to evaluate the polycyclic aromatic hydrocarbon(PAH) mass fraction(qPAH) and the intensity of ultraviolet emission in the studied objects.It is shown that the PAH mass fraction, qPAH, is much lower in these objects than the average Galactic value, implying effective destruction of aromatic particles in HII regions. Estimated radiation field intensities(U) are close to those derived for extragalactic HII complexes. Color indices [F_(24)/F_8], [F_(70)/F_(24)],[F_(160)/F_(24)] and [F_(160)/F_(70)] are compared to criteria proposed to distinguish between regions of ionized hydrogen and planetary nebulae. Also, we relate our results to analogous color indices for extragalactic complexes of ionized hydrogen. 相似文献
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The fact that infrared ring nebulae(IRRNe) are frequently associated with HⅡ regions provides us with an opportunity to study dust at the interface between ionized and neutral gas. In this paper, we analyze the associated infrared(IR) radiation in the range from 8 to 500 μm in the outer and inner parts of32 IRRNe showing a round shape. We aim to determine the morphology of these objects and possible dust evolution processes based on comparing IR radiation towards the ionized and neutral regions. We calculate six slopes between adjacent wavelengths in their spectral energy distributions to trace the difference in physical conditions inside and outside the ionized regions. Using data on these 32 objects, we demonstrate that their morphology is likely 3 D spherical rather than 2 D plane-like. The slope between 70 and 160 μm is the most appropriate tracer of dust temperature in the outer envelope. The larger 8-to-24 μm intensity ratio is associated with smaller intensities at mid-IR, indicating that polycyclic aromatic hydrocarbons(PAHs) may indeed be generated due to larger grain destruction. These data are important for the subsequent theoretical modeling, and determining the dust evolution in HⅡ regions and their envelopes. 相似文献
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