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 assoc...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.展开更多
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, resp...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 hy- drocarbon （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 inten- sities （U） are close to those derived for extragalactic HII complexes. Color indices [F24/F8], [F70/F24], [F160/F24] and [F160/F70] 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.展开更多
基金supported by a grant from the Russian Foundation for Basic Research (18–32–00384)
文摘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.
基金supported by Program 7 of the Presidium of the RAS,“Transitional and Explosive Processes in Astrophysics,”the RFBR(Grant 17-02-00521)
文摘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 hy- drocarbon （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 inten- sities （U） are close to those derived for extragalactic HII complexes. Color indices [F24/F8], [F70/F24], [F160/F24] and [F160/F70] 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.
