Complex Molecules in the L1157 Molecular Outflow

By H. Arce, J. Santiago-García, J. Jørgensen, M. Tafalla, R. Bachiller. 2008

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We report the detection of complex organic molecules in the young protostellar outflow L1157. We identify lines from HCOOCH3, CH3CN, HCOOH, and C2H5OH at the position of the B1 shock in the blueshifted lobe, making it the first time that complex species have been detected toward a molecular outflow powered by a young low-mass protostar. The timescales associated with the warm outflow gas (<2 × 103 yr) are too short for the complex molecules to have formed in the gas phase after the shock-induced sputtering of the grain mantles. It is more likely that the complex species formed in the surface of grains and were then ejected from the grain mantles by the shock. The formation of complex molecules in the grains of low-mass star forming regions must be relatively efficient, and our results show the importance of considering the impact of outflows when studying complex molecules around protostars. The relative abundance with respect to methanol of most of the detected complex molecules is similar to that of hot cores and molecular clouds in the Galactic center region, which suggests that the mantle composition of the dust in the L1157 dark cloud is similar to dust in those regions.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/37c442f4c76bf0211d15fa50e15072cd7b1aabb4

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Citations in the corpus

Our astrochemical heritage (2012, methodology): “Toward this source, not only relatively simple complex molecules, like methanol, have been detected (Codella et al. 2010), but also molecules considered hot cores/corinos tracers, like methyl formate (HCOOCH3), ethanol (C2H5OH), formic acid (HCOOH) and methyl cyanide (CH3CN) (Arce et al. 2008).”
A COLD COMPLEX CHEMISTRY TOWARD THE LOW-MASS PROTOSTAR B1-b: EVIDENCE FOR COMPLEX MOLECULE PRODUCTION IN ICES (2010, background): “The outflow upper limits are comparable to the detected abundances toward another low-mass outflow L1157 (Arce et al. 2008)”
Astrochemistry and compositions of planetary systems (2020, background): “Observations of COMs in outflow shocks, which may originate from sublimation of interstellar ices (Arce et al. 2008), and of PAH formation in clouds (McGuire et al.”
H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices – an extended view on complex organic molecule formation (2016, background): “The same species have also been seen in the cold pre-stellar core B1-b (Cernicharo et al. 2012), in the cold outer envelopes of low-mass protostars (Öberg et al. 2010), and in outflow spots in dark clouds where the ice mantles are liberated by shocks (Arce et al. 2008; Öberg et al. 2011b).”
Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments (2009, background): “The observations by Arce et al. (2008) of HCOOCH3, HCOOH and CH3CH2OH at abundances of∼10−2 with respect to CH3OH towards the low-mass molecular outflow L1157 are especially compelling; this outflow hasbeen above 100 K for a period that is an order of magnitude shorter than is required for the…”