A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices - Astrophysics > Astrophysics of Galaxies - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Gas-phase complex organic molecules have been detected toward a range ofhigh- and low-mass star-forming regions at abundances which cannot be explainedby any known gas-phase chemistry. Recent laboratory experiments show that UVirradiation of CH3OH-rich ices may be an important mechanism for producingcomplex molecules and releasing them into the gas-phase. To test this iceformation scenario we mapped the B1-b dust core and nearby protostar in CH3OHgas using the IRAM 30m telescope to identify locations of efficient non-thermalice desorption. We find three CH3OH abundance peaks tracing two outflows and aquiescent region on the side of the core facing the protostar. The CH3OH gashas a rotational temperature of ~10 K at all locations. The quiescent CH3OHabundance peak and one outflow position were searched for complex molecules.Narrow, 0.6-0.8 km s-1 wide, HCOOCH3 and CH3CHO lines originating in cold gasare clearly detected, CH3OCH3 is tentatively detected and C2H5OH and HOCH2CHOare undetected toward the quiescent core, while no complex molecular lines werefound toward the outflow. The core abundances with respect to CH3OH are ~2.3%and 1.1% for HCOOCH3 and CH3CHO, respectively, and the upper limits are0.7-1.1%, which is similar to most other low-mass sources. The observed complexmolecule characteristics toward B1-b and the pre-dominance of HCO-bearingspecies suggest a cold ice below 25 K, the sublimation temperature of COformation pathway followed by non-thermal desorption through e.g. UV photonstraveling through outflow cavities. The observed complex gas compositiontogether with the lack of any evidence of warm gas-phase chemistry provideclear evidence of efficient complex molecule formation in cold interstellarices.



Autor: Karin I. Oberg, Sandrine Bottinelli, Jes K. Jorgensen, Ewine F. van Dishoeck

Fuente: https://arxiv.org/



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