Formation of complex organic molecules in cold objects: the role of gas-phase reactions

By N. Balucani, Cecilia Ceccarelli, V. Taquet. 2015

217 citations recorded by the source corpus.

While astrochemical models are successful in reproducing many of the observed interstellar species, they have been struggling to explain the observed abundances of complex organic molecules. Current models tend to privilege grain surface over gas phase chemistry in their formation. One key assumption of those models is that radicals trapped in the grain mantles gain mobility and react on lukewarm (>30 K) dust grains. Thus, the recent detections of methyl formate (MF) and dimethyl ether (DME) in cold objects represent a challenge and may clarify the respective role of grain surface and gas phase chemistry. We propose here a new model to form DME and MF with gas phase reactions in cold environments, where DME is the precursor of MF via an efficient reaction overlooked by previous models. Furthermore, methoxy, a precursor of DME, is also synthetized in the gas phase from methanol, which is desorbed by a non-thermal process from the ices. Our new model reproduces fairy well the observations towards L1544. It also explains, in a natural way, the observed correlation between DME and MF. We conclude that gas phase reactions are major actors in the formation of MF, DME and methoxy in cold gas. This challenges the exclusive role of grain-surface chemistry and favours a combined grain-gas chemistry.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/3b58fdcd1997f675a233d530ed402da5ee545d1e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. R. Garrod
2. V. Wakelam
3. M. Ruaud
4. P. Caselli
5. K. Oberg
6. E. Bergin
7. F. Hersant
8. S. Ioppolo

In Atmospheric Science

1. R. Garrod
2. V. Wakelam
3. M. Ruaud
4. F. Hersant
5. E. Bergin
6. S. Ioppolo
7. P. Caselli
8. H. Cuppen

In Spectroscopy

1. V. Wakelam
2. P. Caselli
3. M. Ruaud
4. R. Garrod
5. E. Bergin
6. F. Hersant
7. K. Oberg
8. H. Cuppen

Citations in the corpus

• Grain Surface Models and Data for Astrochemistry (2017, background): “Methanol has been observed abundantly in the ISM (Belloche et al. 2013) and is considered to be a resource for the formation of more complex molecules through surface reactions and after its sublimation in the gas phase (Balucani et al. 2015).”
• Formation of Complex Molecules in Prestellar Cores: A Multilayer Approach (2017, methodology): “This is in contrast to Balucani et al. (2015), who pointed out the existence of a chemical link between CH3OCH3 and HCOOCH3 via the reaction (22), but claimed the main formation routes of CH3OCH2 to be reactions between dimethyl ether and elemental fluorine (F) and clorine (Cl).”
• Astrochemistry and compositions of planetary systems (2020, background): “Finally, sublimated methanol ice can seed a complex gas-phase chemistry at a range of gas temperatures (Charnley et al. 1992; Balucani et al. 2015; Vasyunin et al. 2017).”
• Gas and grain chemical composition in cold cores as predicted by the Nautilus three-phase model (2016, background): “…of molecules such as methyl formate or dimethyl ether in cold regions (Cernicharo et al. 2012; Bacmann et al. 2012) have challenged models and brought some authors (see Balucani et al. 2015, for example) to reassess the relative contribution of gas phase reactions compared to grain chemistry.”