Global photometric analysis of Galactic HII regions

Topchieva, A. P.; Wiebe, D. S.; Kirsanova, M. S.

doi:10.1088/1674-4527/18/8/91

Cited by 6 publications

(10 citation statements)

References 41 publications

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“…Spitzer and WISE maps of the Milky Way Galaxy have revealed more than five thousand ring-like structures, which are commonly referred to as infrared (IR) bubbles, around H ii regions excited by young massive stars, e.g. Churchwell et al (2006Churchwell et al ( , 2007; Deharveng et al (2010); Anderson et al (2011Anderson et al ( , 2014; Simpson et al (2012), and also recent studies by Topchieva et al (2017Topchieva et al ( , 2018a. Spitzer 8 µm and WISE 11 µm emission is commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules, which are excited by the absorption of ultraviolet photons from massive stars (see, for example, classical studies by Sellgren 1984;Leger & Puget 1984) in the photo-dissociation regions (PDRs) on the border between the H ii region and surrounding neutral material.…”

Section: Introductionmentioning

confidence: 99%

Molecular envelope around the HII region RCW 120

Kirsanova

Pavlyuchenkov

Wiebe

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The H ii region RCW 120 is a well-known object, which is often considered as a target to verify theoretical models of gas and dust dynamics in the interstellar medium. However, the exact geometry of RCW 120 is still a matter of debate. In this work, we analyse observational data on molecular emission in RCW 120 and show that 13 CO(2-1) and C 18 O(2-1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C 18 O(3-2) line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature of stalled expansion in this direction. In order to explain a self-absorption dip of the 13 CO(2-1) and 13 CO(3-2) lines, we suggest that RCW 120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map of interstellar extinction. Optically thick 13 CO(2-1) emission and the infrared 8 µm PAH band form a neutral envelope of the H ii region resembling a ring, while the envelope breaks into separate clumps on images made with optically thin C 18 O(2-1) line and far-infrared dust emission.

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Section: Introductionmentioning

confidence: 99%

Molecular envelope around the HII region RCW 120

Kirsanova

Pavlyuchenkov

Wiebe

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…We calculated the 20 cm radio fluxes (F 20cm ) of 91 of these HII regions for which data were presented in the New GPS 20 cm 2 and by Condon et al [23]. We calculated the fluxes within an aperture determined from the 8 µm data in [8,22], which was used for all the wavelengths. We determined the radio fluxes of these 91 objects from the catalog [8] in this way.…”

Section: Radio Continuum Flux At 20 CMmentioning

confidence: 99%

“…One of the main factors in the influence of massive stars on the ISM is their bright ultraviolet (UV) radiation, leading to the formation of surrounding regions of ionized hydrogen (HII regions) [4] with expanding ionization and shock fronts. There is a transition region between such an HII region and the surrounding gas of the host molecular cloud, forming a molecular based on [21,22] and the WISE Catalog of Galactic HII Regions V2.0 1 [3].…”

Section: Introductionmentioning

confidence: 99%

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The Spectral Type of the Ionizing Stars and the Infrared Fluxes of HII Regions

2018

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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. * Electronic address: ATopchieva@inasan.ru arXiv:1811.09093v2 [astro-ph.GA] 26 Nov 2018photodissociation region (PDR). The hydrogen in this region is predominantly neutral, but the degree of ionization of the gas is about 0.01% due to the ionization of carbon. Since the density of the heated gas and dust in a PDR is usually high (see, e.g., the review D. J.Hollenbach и A. G. G. M. Tielens [5]), PDRs are luminous in the infrared (IR). Results from the "Spitzer" IR telescope reveal the presence of thousands of nebulae in the Galactic disk whose shapes are ring-like at 8 µm [6][7][8]. Deharveng et al. [9] showed that most of these ring nebulae are IR reflections of HII regions. Polycyclic aromatic hydrocarbons (PAHs) radiate at 8 µm in PDRs heated by the UV radiation of massive stars. Longer-wavelength IR emission in HII regions is radiated by larger heated dust grains [10,11]. It is interesting that 24 µm emission (the photometric range of the "Spitzer" telescope) is observed inside the 8 µm rings, while longer-wavelength emission (70, 160, 250, and sometimes 350 µm) is coincident with the ring observed at 8 µm [8]. Studies of the spatial distribution of the IR emission in HII regions can provide information about the dust dynamics and the destruction of dust by UV radiation from massive stars (e.g., E. Kruegel [12], J. S. Mathis [13], Pavlychenkov et al. [14], Akimkin et al. [15, 16], Murga et al. [17]). The spectral type and spectral energy distributions of the ionizing stars are key parameters in any model for the dynamics and destruction of dust and PAHs in the ISM [10, 17].Unfortunately, such data are available for only a relatively small fraction of the IR nebulae observed with the "Spitzer" telescope, which were studied before the launch of Spitzer.However, the spectral types of young, massive stars in HII regions can be estimated based on archival data on the radio emission of the heated ionized gas (e.g., [18]). This makes it possible to obtain the parameters of the ionizing sources in large numbers of HII regions.During the expansion of an HII region, there is an increase in the mass of the surrounding neutral, dense envelope due to the action of shocks [19]. However, no analytical and numerical studies of time vari...

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“…В работах [1,2] сформирован каталог данных по областям HII, который является превосходной базой для сравнения с результатами теоретических моделей. В данной работе представлены данные о потоках излучения областей HII.…”

Section: A P Topchieva Institute Of Astronomy Russian Academy Of Sunclassified

Spectral Types of Ionizing Stars and the Infrared Morphology of Hii Regions

Topchieva¹

2020

Proceedings of the 48-Th International Student's Conferences "Physics of Space"

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Представлены данные ранее разработанного каталога, включающего 99 областей ионизованного водорода (HII). Отражены результаты определения потоков в инфракрасном (ИК) и радиоконтинуумах в направлении на области HII. Проведено сравнение оценок ИК-потоков с другими каталогами. Определены примерные спектральные классы ионизующих звезд 42 областей, для которых известны оценки расстояний.

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Global photometric analysis of Galactic HII regions

Cited by 6 publications

References 41 publications

Molecular envelope around the HII region RCW 120

Molecular envelope around the HII region RCW 120

The Spectral Type of the Ionizing Stars and the Infrared Fluxes of HII Regions

Spectral Types of Ionizing Stars and the Infrared Morphology of Hii Regions

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