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 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:
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FileName Lrecl Records Explanations
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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
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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
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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
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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 1978ApJ...224..857E);
2 = Evans et al. (2001ApJ...557..193E 2001ApJ...557..193E);
3 = Shirley et al. (2000ApJS..131..249S 2000ApJS..131..249S);
4 = Toth et al. (2004A&A...420..533T 2004A&A...420..533T);
5 = Hirano et al. (1999sf99..R....181H);
6 = Marcelino et al. (2005ApJ...620..308M 2005ApJ...620..308M);
7 = Kristensen et al. (2012A&A...542A...8K 2012A&A...542A...8K);
8 = Karska et al. (2013A&A...552A.141K 2013A&A...552A.141K);
9 = Hirota et al. (2008PASJ...60...37H 2008PASJ...60...37H);
10 = Chen, Launhardt & Henning (2009ApJ...691.1729C 2009ApJ...691.1729C);
11 = Crimier et al. (2009A&A...506.1229C 2009A&A...506.1229C);
12 = Furlan et al. (2014ApJ...786....6L 2014ApJ...786....6L);
13 = Crimier et al. (2010A&A...516A.102C 2010A&A...516A.102C);
14 = Loinard et al. (2008ApJ...675L..29L 2008ApJ...675L..29L);
15 = Correia, Griffin & Saraceno (2004A&A...418..607C 2004A&A...418..607C).
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Byte-by-byte Description of file: tableb1.dat tableb2.dat
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Bytes Format Units Label Explanations
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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)
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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.
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Byte-by-byte Description of file: tableb[3456789].dat tableb1[012].dat
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Bytes Format Units Label Explanations
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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 mK.km/s TmbdV Line flux for the source
69- 71 I3 mK.km/s e_TmbdV Uncertainty in TmbdV
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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.
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 06-Dec-2017