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|Title:||Shedding light on the formation of the pre-biotic molecule formamide with ASAI||Authors:||López-Sepulcre, A.
Jaber, Ali A.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||449||Issue:||3||First Page:||2438||Abstract:||Formamide (NH<SUB>2</SUB>CHO) has been proposed as a pre-biotic precursor with a key role in the emergence of life on Earth. While this molecule has been observed in space, most of its detections correspond to high-mass star-forming regions. Motivated by this lack of investigation in the low-mass regime, we searched for formamide, as well as isocyanic acid (HNCO), in 10 low- and intermediate-mass pre-stellar and protostellar objects. The present work is part of the IRAM Large Programme ASAI (Astrochemical Surveys At IRAM), which makes use of unbiased broad-band spectral surveys at millimetre wavelengths. We detected HNCO in all the sources and NH<SUB>2</SUB>CHO in five of them. We derived their abundances and analysed them together with those reported in the literature for high-mass sources. For those sources with formamide detection, we found a tight and almost linear correlation between HNCO and NH<SUB>2</SUB>CHO abundances, with their ratio being roughly constant - between 3 and 10 - across 6 orders of magnitude in luminosity. This suggests the two species are chemically related. The sources without formamide detection, which are also the coldest and devoid of hot corinos, fall well off the correlation, displaying a much larger amount of HNCO relative to NH<SUB>2</SUB>CHO. Our results suggest that, while HNCO can be formed in the gas-phase during the cold stages of star formation, NH<SUB>2</SUB>CHO forms most efficiently on the mantles of dust grains at these temperatures, where it remains frozen until the temperature rises enough to sublimate the icy grain mantles. We propose hydrogenation of HNCO as a likely formation route leading to NH<SUB>2</SUB>CHO.||Acknowledgments:||We would like to thank the staff members at IRAM, who greatly helped before, during, and after the ASAI observations. We are also grateful to our anonymous referee, whose comments helped us to improve the manuscript, and to Y. Watanabe, N. Sakai, and S. Yamamoto for very useful discussions. ALS acknowledges financial support from Grant-in-Aids from the Ministry of Education, Culture, Sports, Science, and Technologies of Japan (25108005). This work is partly supported by the French Space Agency CNES (Centre National d’Études Spatiales) and the PRIN INAF 2012 – JEDI and by the Italian Ministero dell'Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA. MK acknowledges support from a Royal Netherlands Academy of Arts and Sciences (KNAW) professor prize. MT and RB gratefully acknowledge partial support from MINECO Grant FIS2012-32096. This article is based on observations carried out with the IRAM 30-m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). It is also based on analysis carried out with the cassis software.||URI:||http://hdl.handle.net/20.500.12386/27331||URL:||https://academic.oup.com/mnras/article/449/3/2438/1113358||ISSN:||0035-8711||DOI:||10.1093/mnras/stv377||Bibcode ADS:||2015MNRAS.449.2438L||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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