THE EFFECT OF BROADBAND SOFT X-RAYS IN SO2-CONTAINING ICES: IMPLICATIONS ON. THE PHOTOCHEMISTRY OF ICES TOWARD YOUNG STELLAR OBJECTS

Autor(es)

Pilling, S. ^[1] ; Bergantini, A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Vale Paraiba UNIVAP, Lab Astroquim & Astrobiol LASA, Sao Jose Dos Campos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 811, n. 2 OCT 1 2015.
• Citações Web of Science: 6

Resumo

We investigate the effects produced mainly by broadband soft X-rays up to 2 keV (plus fast (similar to keV) photoelectrons and low-energy (similar to eV). induced secondary electrons) in the ice mixtures containing H2O:CO2:NH3:SO2 (10:1:1:1) at two different temperatures (50 and 90 K). The experiments are an attempt to simulate the photochemical processes induced by energetic photons in SO2-containing ices present in cold environments in the ices surrounding young stellar objects (YSO) and in molecular clouds in the vicinity of star-forming regions, which are largely illuminated by soft X-rays. The measurements were performed using a high-vacuum portable chamber from the Laboratorio de Astroquimica e Astrobiologia (LASA/UNIVAP) coupled to the spherical grating monochromator beamline at the Brazilian Synchrotron Light Source (LNLS) in Campinas, Brazil. In. situ analyses were performed by a Fourier transform infrared spectrometer. Sample processing revealed the formation of several organic molecules, including nitriles, acids, and other compounds such as H2O2, H3O+, SO3, CO, and OCN-. The dissociation cross section of parental species was on the order of (2-7) x 10(-18) cm(2). The ice temperature does not seem. to affect the stability of. SO2 in the presence of X-rays. Formation cross sections of new species. produced. were also determined. Molecular half-lives at ices toward YSOs due to the presence of incoming soft X-rays were estimated. The low values obtained. employing two different models of the radiation field of YSOs (TW Hydra and typical T-Tauri star). reinforce that soft X-rays are indeed a very efficient source of molecular dissociation in such environments. (AU)

• Processo FAPESP: 12/17248-2 - Estudo da Produção de Moléculas de Interesse Astrobiológico em Experimentos Simulando a lua Encélado na Presença de Fótons UV, Raios-X, Elétrons e Íons Rápidos
• Beneficiário: Alexandre Bergantini de Souza
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 09/18304-0 - Síntese e degradação de espécies moleculares pré-bióticas em atmosferas planetárias, cometas e gelos interestelares simulados
• Beneficiário: Sergio Pilling Guapyassu de Oliveira
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores