Academic Journal
Sampling molecular gas in the Helix planetary nebula: Variation in HNC/HCN with UV flux
| العنوان: | Sampling molecular gas in the Helix planetary nebula: Variation in HNC/HCN with UV flux |
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| المؤلفون: | Bublitz, J., Kastner, J. H., Hily-Blant, P., Forveille, T., Santander-García, M., Alcolea, J., Bujarrabal, V. |
| المساهمون: | Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France |
| المصدر: | ISSN: 0004-6361. |
| بيانات النشر: | HAL CCSD EDP Sciences |
| سنة النشر: | 2022 |
| المجموعة: | Météo-France: HAL |
| مصطلحات موضوعية: | astrochemistry, line: identification, methods: observational, planetary nebulae: individual: NGC 7293, radio lines: general, [SDU]Sciences of the Universe [physics], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] |
| الوصف: | International audience ; Context. Observations of molecular clouds, prestellar cores, and protoplanetary disks have established that the HNC/HCN ratio may be a potent diagnostic of molecular gas physical conditions. The processes that govern the relative abundances of these molecules nevertheless remain poorly understood. Aims: We seek to exploit the wide range of UV irradiation strengths within the ∼pc diameter Helix planetary nebula to explore the potential role of UV radiation in driving HNC/HCN. Methods: We performed IRAM 30 m and APEX 12 m radio line observations across six positions within the Helix Nebula, making use of radiative transfer and photodissociation modeling codes to interpret the results for line intensities and line ratios in terms of the molecular gas properties. Results: We have obtained the first detections of the plasma-embedded Helix molecular knots (globules) in HCN, HNC, HCO + , and other trace molecules. Analysis of the HNC/HCN integrated line intensity ratio reveals an increase with radial distance from the Helix central star. In the context of molecular line ratios of other planetary nebulae from the literature, the HNC/HCN ratio appears to be anticorrelated with UV emission over four orders of magnitude in incident flux. Models of the photodissociation regions within the Helix using the RADEX and Meudon codes reveal strong constraints on the column density (1.5-2.5 × 10 12 cm −2 ) of the molecular gas, as well as pressure and temperature. Analysis of the molecular ion HCO + across the Helix indicates that X-ray irradiation is likely driving HCO + production in the outer regions of planetary nebulae, where photodissociation is limited but cold gas and ionized molecules are abundant. Conclusions: Although the observational results clearly indicate that UV irradiation is important in determining the HNC/HCN ratio, our photodissociation region modeling indicates that the UV flux gradient alone cannot reproduce the observed variation in HNC/HCN across the Helix Nebula. Instead, HNC/HCN ... |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| Relation: | info:eu-repo/semantics/altIdentifier/arxiv/2111.08816; insu-03705370; https://insu.hal.science/insu-03705370; https://insu.hal.science/insu-03705370/document; https://insu.hal.science/insu-03705370/file/aa41778-21.pdf; ARXIV: 2111.08816; BIBCODE: 2022A&A.659A.197B |
| DOI: | 10.1051/0004-6361/202141778 |
| الاتاحة: | https://insu.hal.science/insu-03705370 https://insu.hal.science/insu-03705370/document https://insu.hal.science/insu-03705370/file/aa41778-21.pdf https://doi.org/10.1051/0004-6361/202141778 |
| Rights: | info:eu-repo/semantics/OpenAccess |
| رقم الانضمام: | edsbas.4105EB4 |
| قاعدة البيانات: | BASE |
| DOI: | 10.1051/0004-6361/202141778 |
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