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

Author(s)

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

Affiliation

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

• Document type: Journal article
• Source: ASTROPHYSICAL JOURNAL; v. 811, n. 2 OCT 1 2015.
• Web of Science Citations: 6

Abstract

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)

• FAPESP's process: 12/17248-2 - Production of molecules with astrobiological interest in experiments simulating the moon Enceladus in the presence of UV photons, X-rays, electrons, and fast ions
• Grantee: Alexandre Bergantini de Souza
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 09/18304-0 - Synthesis and degradation of prebiotic molecular species at planetary atmospheres, comets and interstellar ice analogs
• Grantee: Sergio Pilling Guapyassu de Oliveira
• Support Opportunities: Research Grants - Young Investigators Grants