The role of external far-ultraviolet irradiation in the survival of astrophysical ices in Elias 29

The survival of astrophysical ices in star-forming regions depends on the suitability of temperature, density and radiation conditions. In this article, the role of the interstellar radiation field (ISRF) on ices in Elias 29 is addressed. This object is the most luminous protostar in the rho Oph E molecular cloud and is surrounded by many young stellar objects only a few arcmin distant. In addition, two other bright BV stars (S1 and HD 147889) enhance the external irradiation in Elias 29. This study was carried out using the Monte Carlo radiative transfer code RADMC-3D assuming internal and external irradiation. As result, we found that HD 147889 dominates the ISRF, rather than the closest protostars, and contributes to enhancing the external irradiation by 44 times the standard value. Furthermore, remarkable effects are observed in the far-infrared (FIR) spectrum, as well as in the near-infrared (near-IR) image. Additionally, the snowline positions of volatile compounds, such as CO, O-2, N-2 and CH4, are redefined to a toroidal-shaped morphology in the envelope, with low far-ultraviolet (FUV) flux (10(-7)erg cm(-2) s(-1)). In such a scenario, the formation of complex molecules as the result of hydrogenation or oxygenation of volatile species is expected to be severely affected.