Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)

By Arnaud Belloche, H. S. P. Müller, R. Garrod, K. Menten. 2015

139 citations recorded by the source corpus.

Deuteration is a powerful tracer of the history of the cold prestellar phase in star forming regions. Apart from methanol, little is known about deuterium fractionation of complex organic molecules in the interstellar medium, especially in high mass star forming regions. We use a spectral line survey performed with ALMA to search for deuterated complex organic molecules toward the hot molecular core Sgr B2(N2). Population diagrams and integrated intensity maps are constructed to fit rotational temperatures and emission sizes for each molecule. Column densities are derived by modelling the full spectrum under the LTE assumption. The results are compared to predictions of two astrochemical models that treat the deuteration process. We report the detection of CH2DCN toward Sgr B2(N2) with a deuteration level of 0.4%, and tentative detections of CH2DOH, CH2DCH2CN, the chiral molecule CH3CHDCN, and DC3N with levels in the range 0.05%-0.12%. A stringent deuteration upper limit is obtained for CH3OD (<0.07%). Upper limits in the range 0.5-1.8% are derived for the three deuterated isotopologues of vinyl cyanide, the four deuterated species of ethanol, and CH2DOCHO. Ethyl cyanide is less deuterated than methyl cyanide by at least a factor five. Except for methyl cyanide, the measured deuteration levels lie at least a factor four below the predictions of current astrochemical models. The deuteration levels in Sgr B2(N2) are also lower than in Orion KL by a factor of a few up to a factor ten. The discrepancy between the deuteration levels of Sgr B2(N2) and the predictions of chemical models, and the difference between Sgr B2(N2) and Orion KL may both be due to the higher kinetic temperatures that characterize the Galactic Center region compared to nearby clouds. Alternatively, they may result from a lower overall abundance of deuterium itself in the Galactic Center region by up to a factor ten.

Subfields: Astronomy and Astrophysics, Biomedical Engineering, Organic Chemistry

View Paper: https://www.semanticscholar.org/paper/e6584535a1b5f20cd3711d978f609e47be4c78af

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. E. Bergin
2. K. Oberg
3. B. McGuire
4. N. Madhusudhan
5. R. Garrod
6. E. Dishoeck
7. P. Caselli
8. Cecilia Ceccarelli

In Biomedical Engineering

1. B. McGuire
2. K. Oberg
3. E. Bergin

In Organic Chemistry

1. B. McGuire
2. K. Oberg
3. E. Bergin

Citations in the corpus

• 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules (2018, background): “Interferometric observations in these regions, however, can often isolate individuals cores, significantly narrowing the linewidths to a few km s−1 (Belloche et al. 2016).”
• Astrochemistry and compositions of planetary systems (2020, background): “2013) and complex organics (Charnley et al. 1997; Belloche et al. 2016) in hot corinos are highly deuterated, which, as discussed in the previous section, can be traced back to the formation conditions of water and CH3OH in molecular clouds and cloud cores (Aikawa et al.”