Shedding light on the formation of the pre-biotic molecule formamide with ASAI

Abstract

Formamide (NH 2 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 broadband spectral surveys at millimetre wavelengths. We detected HNCO in all the sources and NH 2 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 2 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 2 CHO. Our results suggest that, while HNCO can be formed in the gas phase during the cold stages of star formation, NH 2 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 2 CHO.

Decrease of the organic deuteration during the evolution of Sun-like protostars: the case of SVS13-A

“…Three lines of H 13 2 CO (with frequencies 137.45 GHz, 141.98 GHz, and 146.64 GHz) and one line of HDCO (with frequency 134.2848) are detected in the 2 mm band and they are affected by contamination of emission in the off positions (see Sect. 2 for details on the observing techniques), consistently with the analysis reported by López-Sepulcre et al (2015), using ASAI spectra. The contaminated lines correspond to a size of the telescope HPBW > 16 ′′ .…”

“…Examples of the detected line profiles in TMB scale are shown in Figure 1. The peak velocities of the detected lines are between +8 km s −1 and +9 km s −1 , being consistent, once considered the fit uncertainties, with the systemic velocity of both A and B component of SVS13 (+8.6 km s −1 , Chen et al 2009;López-Sepulcre et al 2015). We fitted the lines with a Gaussian function, and excluded from the analysis those lines with |v peak -vsys| >0.6 km/s plausibly affected by line blending.…”

Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

“…A cold complex chemistry was discovered in B1-b via the detections of CH 3 OH, HCOOCH 3 , CH 3 CHO, trans-HCOOH, C 4 H, HNCO, and the H 2 C 3 O isomers (Sakai et al 2009a;Öberg et al 2010;López-Sepulcre et al 2015;Cuadrado et al 2016;Loison et al 2016), and tentatively CH 3 OCH 3 (Öberg et al 2010), as well as CH 3 O (Cernicharo et al 2012). These previous detections were all reported at levels well below the noise level obtained in our observations.…”

Chemical segregation in hot cores with disk candidates

“…It has previously been proposed (Bisschop et al 2007;Mendoza et al 2014;López-Sepulcre et al 2015) based on single dish observations that formamide (NH 2 CHO) forms through the hydrogenation of HNCO because there appears to be a constant abundance ratio across a large range of source luminosities and masses. Figure 12 shows that these two species have almost the same spatial extent in G35.20 B and their emission peaks are only 0.15 (or ∼300 AU) apart in G35.20 B.…”

“…The search continues for the precursors of life like the simplest amino acid, glycine (H 2 NCH 2 COOH), but complex organic species with up to 12 atoms have already been detected 1 . These include important precursors to amino acids like aminoacetonitrile (H 2 NCH 2 CN), detected by Belloche et al (2008); the simplest monosaccharide sugar glycolaldehyde (CH 2 OHCHO), first observed in a hot molecular core outside the galactic center by Beltrán et al (2009); and formamide (NH 2 CHO) extensively studied by López-Sepulcre et al (2015). With ALMA we have the ability to detect hot cores and study their properties in detail to determine how the spatial distribution of COMs influences the formation of massive stars.…”