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J/MNRAS/449/2438   Formamide detection with ASAI-IRAM    (Lopez-Sepulcre+, 2015)

Shedding light on the formation of the pre-biotic molecule formamide with ASAI. Lopez-Sepulcre A., Jaber A.A., Mendoza E., Lefloch B., Ceccarelli C., Vastel C., Bachiller R., Cernicharo J., Codella C., Kahane C., Kama M., Tafalla M. <Mon. Not. R. Astron. Soc., 449, 2438-2458 (2015)> =2015MNRAS.449.2438L (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Interstellar medium ; YSOs ; Spectroscopy Keywords: astrochemistry - methods: observational - stars: formation - ISM: abundances - ISM: molecules Abstract: Formamide (NH2CHO) 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 NH2CHO 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 NH2CHO 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 NH2CHO. Our results suggest that, while HNCO can be formed in the gas-phase during the cold stages of star formation, NH2CHO 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 NH2CHO. Description: Our source sample consists of 10 well-known pre-stellar and protostellar objects representing different masses and evolutionary states, thus providing a complete view of the various types of objects encountered along the first phases of star formation. The data presented in this work were acquired with the IRAM 30-m telescope near Pico Veleta (Spain) and consist of unbiased spectral surveys at millimetre wavelengths. These are part of the Large Programme ASAI, whose observations and data reduction procedures will be presented in detail in an article by Lefloch & Bachiller (in preparation). Briefly, we gathered the spectral data in several observing runs between 2011 and 2014 using the EMIR receivers at 3 mm (80-116 GHz), 2 mm (129-173 GHz), and 1.3 mm (200-276 GHz). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 103 10 Source sample and their properties tableb1.dat 81 84 NH2CHO transitions searched for in this study and 3σ detections tableb2.dat 81 21 HNCO transitions searched for in this study and 3σ detections tableb3.dat 71 2 L1544: Gaussian fits to the detected HNCO lines tableb4.dat 71 3 TMC-1: Gaussian fits to the detected HNCO lines tableb5.dat 71 4 B1: Gaussian fits to the detected HNCO lines tableb6.dat 71 4 L1527: Gaussian fits to the detected HNCO lines tableb7.dat 71 4 L1157mm: Gaussian fits to the detected HNCO lines tableb8.dat 71 17 IRAS 4A: Gaussian fits to the detected NH2CHO and HNCO lines tableb9.dat 71 28 I16293: Gaussian fits to the detected NH2CHO and HNCO lines (intensity in T*ant units) tableb10.dat 71 32 SVS13A: Gaussian fits to the detected NH2CHO and HNCO lines tableb11.dat 71 10 Cep E: Gaussian fits to the detected NH2CHO and HNCO lines tableb12.dat 71 30 OMC-2 FIR 4: Gaussian fits to the detected NH2CHO and HNCO lines
See also: J/A+A/473/177 : A search for pre-biotic molecules (Wirstrom+, 2007) J/A+A/548/A71 : Spectroscopy and ISM detection of formamide (Motiyenko+, 2012) J/A+A/556/A57 : Transitions in OMC-2 FIR 4 in the far-IR (Kama+, 2013) J/A+A/606/A82 : Observed chemical structure of L1544 (Spezzano+, 2017) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 7 A7 --- Survey Survey identification (ASAI or TIMASSS) 9- 19 A11 --- Name Source name 21- 22 I2 h RAh Hour of Right Ascension (J2000) 24- 25 I2 min RAm Minute of Right Ascension (J2000) 27- 31 F5.2 s RAs Second of Right Ascension (J2000) 33 A1 --- DE- Sign of the Declination (J2000) 34- 35 I2 deg DEd Degree of Declination (J2000) 37- 38 I2 arcmin DEm Arcminute of Declination (J2000) 40- 43 F4.1 arcsec DEs Arcsecond of Declination (J2000) 45- 49 F5.1 km/s Vlsr Local Standard of Rest velocity 51- 53 I3 pc Dist Distance 55- 59 F5.2 Msun Mass Mass 61- 65 F5.1 Lsun Lbol ? Bolometric luminosity 67- 82 A16 --- Type Source type (1) 84- 90 A7 --- Ref Reference(s) (2) 92-103 A12 --- FileName File containing data for this source
Note (1): Type as follows: PSC = Pre-stellar core; HC = Hot corino; WCCC = Warm carbon-chain chemistry; IM = Intermediate-mass. Note (2): Reference as follows: 1 = Elias (1978ApJ...224..857E); 2 = Evans et al. (2001ApJ...557..193E); 3 = Shirley et al. (2000ApJS..131..249S); 4 = Toth et al. (2004A&A...420..533T); 5 = Hirano et al. (1999sf99..R....181H); 6 = Marcelino et al. (2005ApJ...620..308M); 7 = Kristensen et al. (2012A&A...542A...8K); 8 = Karska et al. (2013A&A...552A.141K); 9 = Hirota et al. (2008PASJ...60...37H); 10 = Chen, Launhardt & Henning (2009ApJ...691.1729C); 11 = Crimier et al. (2009A&A...506.1229C); 12 = Furlan et al. (2014ApJ...786....6L); 13 = Crimier et al. (2010A&A...516A.102C); 14 = Loinard et al. (2008ApJ...675L..29L); 15 = Correia, Griffin & Saraceno (2004A&A...418..607C).
Byte-by-byte Description of file: tableb1.dat tableb2.dat
Bytes Format Units Label Explanations
1- 17 A17 --- Trans Transition 19- 28 F10.3 MHz nu Frequency of the transition ν 30- 34 F5.1 K Eu Upper level energy 36- 41 F6.2 10-5/s Aul Transition rate 43- 44 I2 arcsec thetab [9/30] Telescope beam size θb 46- 47 A2 --- OMC-2 [Y*NB- ] 3σ detection for OMC-2 FIR 4 (1) 49- 50 A2 --- CepE [Y*N- ] 3σ detection for CepE (1) 52- 53 A2 --- SVS13A [Y*NB- ] 3σ detection for SVS13A (1) 55- 56 A2 --- IRAS4A [Y*bNB ] 3σ detection for IRAS4A (1) 58- 59 A2 --- I16293 [Y*bcNB ] 3σ detection for I16293 (1) 61 A1 --- L1157 [YN] 3σ detection for L1157 (1) 63 A1 --- L1527 [YN] 3σ detection for L1527 (1) 65 A1 --- B1 [YN-] 3σ detection for B1 (1) 67 A1 --- L1544 [YN-] 3σ detection for L1544 (1) 69 A1 --- TMC-1 [YN-] 3σ detection for TMC-1 (1) 71- 81 A11 --- Blend Blended line identifier (2)
Note (1): Detection as follows: Y = Detected above Tmb=3σ; Y* = Weakly detected (S/N∼2-3; see Section 4.1); Yb = Detected but with an anomalously high flux (maybe blended): removed from analysis; Yc = Blended with an unidentified feature: removed from analysis; N = Undetected; B = Possibly detected but blended; - = Not observed. Note (2): Blended line in tableb2 : CH3OH at 241.774 GHz.
Byte-by-byte Description of file: tableb[3456789].dat tableb1[012].dat
Bytes Format Units Label Explanations
1 A1 --- Mol [NH] Molecule identification (1) 3- 19 A17 --- Trans Transition 20- 21 A2 --- n_Trans [w *] Note on Trans (2) 23- 32 F10.3 MHz nu Frequency of the transition ν 34- 37 F4.1 mK rms rms value 39- 43 F5.1 mK Tpeak Peak temperature 45- 46 I2 mK e_Tpeak Uncertainty in Tpeak 48- 52 F5.1 km/s Vlsr Local Standard of Rest velocity 54- 55 I2 km/s e_Vlsr Uncerainty in Vlsr 57- 59 F3.1 km/s DeltaV Velocity difference 61- 62 I2 km/s e_DeltaV Uncertainty in DeltaV 64- 67 I4 TmbdV Line flux for the source 69- 71 I3 e_TmbdV Uncertainty in TmbdV
Note (1): Molecule as follows: N = NH2CHO; H = HNCO. Note (2): Note as follows: w = Transition weakly detected (see Table B1) but included in the analysis for completeness; * = Transition affected by emission at OFF position: lower limit point in the rotational diagram.
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 06-Dec-2017
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