The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium

Abstract

Formamide (NH2CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic
molecules. Its formation mechanism is still debated, however. Observations of formamide, related species, and their isopotologues
may provide useful clues to the chemical pathways leading to their formation. The Protostellar Interferometric Line Survey (PILS)
represents an unbiased, high angular resolution and sensitivity spectral survey of the low-mass protostellar binary IRAS 16293–2422
with the Atacama Large Millimeter/submillimeter Array (ALMA). For the first time, we detect the three singly deuterated forms of
NH2CHO (NH2CDO, cis- and trans-NHDCHO), as well as DNCO towards the component B of this binary source. The images reveal
that the different isotopologues are all present in the same region. Based on observations of the 13C isotopologues of formamide and
a standard 12C/
13C ratio, the deuterium fractionation is found to be similar for the three different forms with a value of about 2%. The
DNCO/HNCO ratio is also comparable to the D/H ratio of formamide (∼1%). These results are in agreement with the hypothesis that
NH2CHO and HNCO are chemically related through grain-surface formation.

Full text

Astronomy &Astrophysics manuscript no. NH2CHO_PILS_aa_v6 c
ESO 2016
May 6, 2016
Letter to the Editor
The ALMA-PILS survey: First detections of deuterated formamide
and deuterated isocyanic acid in the interstellar medium
A. Coutens1, J. K. Jørgensen2, M. H. D. van der Wiel2, H. S. P. Müller3, J. M. Lykke2, P. Bjerkeli2,4, T. L. Bourke5, H.
Calcutt2, M. N. Drozdovskaya6, C. Favre7, E. C. Fayolle8, R. T. Garrod9, S. K. Jacobsen2, N. F. W. Ligterink6, K. I.
Öberg8, M. V. Persson6, E. F. van Dishoeck6,10, and S. F. Wampfler2
1Department of Physics and Astronomy, University College London, Gower St., London, WC1E 6BT, UK
e-mail: a.coutens@ucl.ac.uk
2Centre for Star and Planet Formation, Niels Bohr Institute & Natural History Museum of Denmark, University of Copenhagen,
Øster Voldgade 5-7, DK-1350 Copenhagen K., Denmark
3I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
4Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
5SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK
6Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
7Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274, UJF-Grenoble 1/CNRS, 38041 Grenoble, France
8Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
9Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904, USA
10 Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany
Received xxx; accepted xxx
ABSTRACT
Formamide (NH2CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different
prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species and their isopo-
tologues may provide useful clues to the chemical pathways leading to their formation. The Protostellar Interferometric Line Survey
(PILS) represents an unbiased high angular resolution and sensitivity spectral survey of the low-mass protostellarbinary IRAS 16293–
2422 with the Atacama Large Millimeter/submillimeter Array (ALMA). We detect for the first time the three singly deuterated forms
of NH2CHO (NH2CDO, cis- and trans-NHDCHO) as well as DNCO towards the component B of this binary source. The images
reveal that the different isotopologues all are present in the same region. Based on the observations of the 13C isotopologues of for-
mamide and a standard 12C/13 C ratio, the deuterium fractionation is found to be similar for the three different forms with a value of
about 2%. The DNCO/HNCO ratio is also comparable to the D/H ratio of formamide (∼1%). These results are in agreement with the
hypothesis that NH2CHO and HNCO are chemically related through grain surface formation.
Key words. astrochemistry – astrobiology – stars: formation – stars: protostars – ISM: molecules – ISM: individual object
(IRAS 16293–2422)
1. Introduction
Formamide (NH2CHO), also known as methanamide, contains
the amide bond (–N–C(=O)–), which plays an important role in
the synthesis of proteins. This molecule is a precursor for poten-
tial compounds of genetic and metabolic interest (Saladino et al.
2012). Interestingly, it is present in various astrophysical envi-
ronments: high-mass star-forming regions (e.g, Bisschop et al.
2007; Adande et al. 2013), low-mass protostars (Kahane et al.
2013; López-Sepulcre et al. 2015), shocked regions (Yamaguchi
et al. 2012; Mendoza et al. 2014), a translucent cloud (Corby
et al. 2015), comets (Bockelée-Morvan et al. 2000; Biver et al.
2014; Goesmann et al. 2015) and even an extragalactic source
(Muller et al. 2013).
The formation of formamide is still not clearly understood:
several routes have been proposed, both in the gas phase and
on the grain surfaces. In the gas phase, many ion-molecule re-
actions have been ruled out as not sufficiently efficient due to
endothermicity or high energy barriers (see e.g. Redondo et al.
2014a,b). A neutral-neutral reaction between H2CO and NH2
was however shown to be barrierless and could account for the
abundance of formamide in some sources (Barone et al. 2015).
On the grain surface, formamide is suggested to form through
the reaction between HCO and NH2(Jones et al. 2011; Garrod
2013) and/or hydrogenation of isocyanic acid, HNCO. In partic-
ular, the latter suggestion is supported by a strong correlation be-
tween the HNCO and NH2CHO abundances in different sources
(Bisschop et al. 2007; Mendoza et al. 2014; López-Sepulcre et al.
2015). However, an experiment based on the H bombardment of
HNCO at low temperature has recently shown that this reaction
is not efficient in cold environments (Noble et al. 2015). Instead,
other pathways to HNCO and NH2CHO on grains have been
suggested, either with or without UV or ion bombardment (see
e.g. Kaˇ
nuchová et al. 2016 and references therein).
Measurements of isotopic fractionation may help to con-
strain formation pathways of molecules as isotopic fractiona-
tion (especially deuteration) is sensitive to physical conditions
such as density and temperature. Until recently, the study of
deuteration in solar-type protostars was mainly limited to rel-
atively small and abundant molecules, such as H2O, HCO+,
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A&A proofs: manuscript no. NH2CHO_PILS_aa_v6
HCN, H2CO, and CH3OH. Even though the deuterium frac-
tionation is known to be enhanced in low-mass protostars (see
e.g., Ceccarelli et al. 2007), measurements of lines of deuter-
ated complex organic molecules (COMs) still require high sen-
sitivity observations. So far, only deuterated methyl formate
and dimethyl ether have been detected towards the low-mass
protostar IRAS 16293–2422 (hereafter IRAS16293) by Demyk
et al. (2010) and Richard et al. (2013). With the Atacama Large
Millimeter/submillimeter Array (ALMA), it is now possible
to search for the isotopologues of complex and less abundant
species. In this Letter, we report the first detection of the three
singly deuterated forms of formamide as well as DNCO to-
wards IRAS16293. These observations mark the first detections
of those isotopologues in the interstellar medium.
2. Observations
An ALMA unbiased spectral survey of the binary protostar
IRAS16293 was recently carried out in the framework of the
“Protostellar Interferometric Line Survey”1(PILS; Jørgensen
et al. submitted). The observations were centered on a position
at equal distance between the sources A and B that are separated
by ∼500. A full description of the survey and the data reduction
can be found in Jørgensen et al. (submitted). For this work, we
use the part of the large spectral survey obtained in Band 7 be-
tween 329.15 GHz and 362.90 GHz both with the 12m array and
the Atacama Compact Array (ACA). The spectral resolution of
these observations is 0.244 MHz (i.e. ∼0.2 km s−1). After combi-
nation of the 12m and ACA data, the final spectral line datacubes
show a sensitivity better than 5 mJy beam−1km s−1. The beam
sizes range between 0.400 and 0.700. Additional observations in
Bands 3 and 6 cover narrow spectral ranges and consequently a
very limited number of transitions of formamide isotopologues.
After the analysis of Band 7, we checked that the results are con-
sistent with these lower frequency observations.
3. Analysis and results
To search for the isotopologues of formamide, we use the spec-
trum extracted at the same position as in Lykke et al. (to be sub-
mitted), i.e. a position offset by ∼0.500 from the continuum peak
of source B in the South West direction (αJ2000=16h32m22s
.58,
δJ2000=-24◦28032.800 ). Although the lines are brighter at the po-
sition of the continuum peak, the presence of both absorption
and emission makes analysis difficult. At the selected position,
most of the lines present Gaussian profiles and are relatively
bright compared to other positions. In source A, the lines are
quite broad leading to significant line confusion that prevents
the search for isotopologues of complex species (e.g. Jørgensen
et al. 2012). This Letter is therefore focused on source B only.
We identify several unblended lines that can be assigned
to the three singly deuterated forms of NH2CHO and to
NH213CHO, DNCO, and HN13 CO (see Table 1). These mark
the first detections of NH2CDO, cis-NHDCHO, trans-NHDCHO
and DNCO in the interstellar medium. The list of unblended
lines can be found in the Appendix. Maps of the integrated line
emission from representative lines from the different isotopo-
logues towards source B are shown in Figure 1. The emission
of the different lines clearly arise from a similar compact region
in the vicinity of IRAS16293B. A hole is observed in the maps
due to the absorptions that are produced against the strong con-
tinuum at the continuum peak position. For DNCO the larger
1http://youngstars.nbi.dk/PILS/
Table 1. Number of lines used in the analysis of the isotopologues of
NH2CHO and HNCO and column densities derived for Tex =300 K and
a source size of 0.500.
Species # of lines Eup (K) N(cm−2)
NH2CDO 12 146 – 366 2.1 ×1014
cis-NHDCHO 11 146 – 307 2.1 ×1014
trans-NHDCHO 11 151 – 332 1.8 ×1014
NH213CHO 10 152 – 428 1.5 ×1014
15NH2CHO – – ≤1.0 ×1014 (a)
NH2CH18O – – ≤0.8 ×1014 (a)
DNCO 4 150 – 751 3.0 ×1014
HN13CO 8 127 – 532 4.0 ×1014
H15NCO – – ≤2.0 ×1014 (a)
HNC18O – – ≤1.5 ×1014 (a)
Notes. (a)3σupper limit.
beam size for the observations of this transition masks the ab-
sorption. The spatial variations that are observed among the dif-
ferent species are probably due to different line excitation or line
brightness. In particular, HNCO seems to be slightly more ex-
tended than NH2CHO, but this is most likely due to the fact that
the HNCO lines are particularly bright compared to the HNCO
and formamide isotopologues.
To constrain the excitation temperatures and column densi-
ties of the different species, we produce a grid of synthetic spec-
tra assuming Local Thermodynamical Equilibrium (LTE). We
predict the spectra for different excitation temperatures between
100 and 300 K with a step of 25 K and for different column den-
sities between 1 ×1013 and 1 ×1017 cm−2. First, the column den-
sity is roughly estimated using relatively large steps, then refined
using smaller steps around the best fit solution. We determine
the best fit model using a χ2method comparing the observed
and synthetic spectra at ±0.5 MHz around the rest frequency of
the predicted emission lines. We carefully check that the best
fit model does not predict any lines not observed in the spec-
tra. For the deuterated forms, the models are in agreement with
the observations for excitation temperatures between 100 and
300 K. However, for NH213CHO and HN13CO, a model with
a high excitation temperature accounts much better for the ob-
served emission than a model with a low excitation temperature
(see Figs B.4 and B.6). An excitation temperature of 300 K was
consequently adopted for the analysis of the different isotopo-
logues. This excitation temperature is similar to that derived for
glycolaldehyde and ethylene glycol (Jørgensen et al. 2012, sub-
mitted), but higher than what is found for acetaldehyde, ethylene
oxide and propanal (∼125 K, Lykke et al. to be submitted). The
derived column densities, assuming a linewidth of 1 kms−1and
a source size of 0.500 (Jørgensen et al. submitted; Lykke et al. to
be submitted), are summarized in Table 1. The uncertainties on
the column densities are all estimated to be within a factor of 2
(including the uncertainty on both the excitation temperature and
the baseline subtraction). The upper limits are estimated visually
by comparison of the synthetic spectra with the observations on
the entire spectral range. Figure 2 shows three lines of each iso-
topologue with the best-fit model. The models for all the lines
are shown in Appendix B.
The column densities of NH213CHO and HN13 CO are es-
timated to be 1.5 ×1014 cm−2and 4 ×1014 cm−2, respectively.
Assuming a 12C/13 C ratio of 68 (Milam et al. 2005), the col-
umn densities for the main isotopologues of formamide and iso-
cyanic acid are predicted to be 1 ×1016 cm−2and 3 ×1016 cm−2.
Article number, page 2 of 10

A. Coutens et al.: The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid
Fig. 1. Integrated intensity maps of NH2CHO, HNCO and their isotopo-
logues towards source B. The position of the continuum peak of source
B is indicated with a red cross, while the position where the spectrum
was extracted is shown with a red circle. The beam sizes are shown in
grey in the bottom right corner of each panel. The contour levels start
for the main isotopologue of HNCO at 0.05 Jy km s−1with a step of
0.05 Jy km s−1. For the other species, the levels are 0.02, 0.03, 0.04,
0.06, 0.08, 0.1 and 0.12 Jy kms−1.
With these column densities, several NH2CHO lines and all of
the HNCO lines are overproduced, indicating that they are opti-
cally thick. The model of formamide is, however, in agreement
with the few lines with the lowest opacities (see Figs. B.7 and
B.8). NH2CH18O has also been searched for, but is not detected
with a 3σupper limit of 8 ×1013 cm−2. The non-detection of this
isotopologue is consistent with the 16O/18 O ratio of 560 in the in-
terstellar medium (Wilson 1999), which gives N(NH2CH18O) =
2×1013 cm−2. Similarly, HNC18O is not detected either with a
3σupper limit of 1.5 ×1014 cm−2, which is consistent with its
expected column density of 5 ×1013 cm−2.
Using the column densities derived for the 13C isotopo-
logues and a standard 12C/13 C ratio, the deuterium fractiona-
tion in NH2CHO is about 2% for the three deuterated forms
and the DNCO/HNCO ratio is similar (∼1%). If the 12C/13 C ra-
tio is lower (∼30) as reported for glycolaldehyde by Jørgensen
et al. (submitted), the D/H ratios of formamide and isocyanic
acid would be about 4-5% and 2-3%, respectively.
329.990 329.995 330.000
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
(Jy/beam)
342.320 342.325
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
354.415 354.420
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
346.585 346.590
-0.02
0.00
0.02
0.04
0.06
0.08
(Jy/beam)
346.825 346.830
-0.02
0.00
0.02
0.04
0.06
0.08
347.265 347.270
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
333.690 333.695
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
(Jy/beam)
333.810 333.815
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
353.350 353.355 353.360
-0.02
0.00
0.02
0.04
0.06
339.175 339.180 339.185
-0.02
-0.01
0.00
0.01
0.02
0.03
(Jy/beam)
339.210 339.215
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
360.530 360.535
-0.02
0.00
0.02
0.04
0.06
344.625 344.630 344.635
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
(Jy/beam)
346.555 346.560
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
348.595 348.600 348.605
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
329.590 329.595 329.600
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
(Jy/beam)
330.860 330.865
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
350.340 350.345
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
NH2CDOcis-NHDCHOtrans-NHDCHONH2
13CHODNCOHN13CO
Fig. 2. Black: Detected lines of NH2CDO, cis-NHDCHO, trans-
NHDCHO, NH213CHO, DNCO and HN13 CO. Red: Best-fit model.
We also search for the 15N isotopologues of formamide and
isocyanic acid. A couple of transitions could tentatively be as-
signed to 15NH2CHO, but these lines are close to the noise level
and possibly blended with other species. For H15NCO, the uncer-
tainties on the frequencies of some of the transitions are rather
large, preventing any firm detection. Based on a standard 12C/13C
ratio, lower limits of 100 and 138 are obtained for the 14N/15N
ratios of formamide and HNCO respectively.
4. Discussion and conclusion
Our derived ratio in IRAS16293 for HNCO/NH2CHO, ∼3, is
consistent with the ratios found in warm sources in previous
studies (Bisschop et al. 2007; Mendoza et al. 2014; López-
Sepulcre et al. 2015). Thanks to our interferometric observa-
tions, we also confirm that these two species are spatially corre-
lated. The deuterium fractionation ratios of these two molecules
are also similar, reinforcing the hypothesis that they are chemi-
cally related. We discuss here possible scenarios for the forma-
tion of these species in the warm inner regions of protostars.
Assuming that the deuteration of formaldehyde in the region
probed by the ALMA observations of formamide is similar to
the value derived with single-dish observations (∼15%, Loinard
et al. 2000), we can discuss the possibility for the gas-phase for-
Article number, page 3 of 10

A&A proofs: manuscript no. NH2CHO_PILS_aa_v6
mation mechanism proposed by Barone et al. (2015), H2CO +
NH2→NH2CHO +H. According to this reaction, the deuter-
ated form NHDCHO would result from the reaction between
NHD and H2CO, while NH2CDO would form from NH2and
HDCO. We would consequently expect a higher deuteration for
NH2CDO compared to the observations unless the reaction be-
tween NH2and HDCO leads more efficiently to NH2CHO and D
compared to NH2CDO and H. Theoretical or experimental stud-
ies of the branching ratios of these reactions would be needed to
rule out this scenario. The determination of the HDCO/H2CO
ratio from the PILS survey is also necessary. Nevertheless, it
should be noted that so far there is no proposed scenario in the
gas phase that could explain the correlation with HNCO.
Although it was recently shown that NH2CHO does not
form by hydrogenation of HNCO on grain surfaces (Noble et al.
2015), several other proposed mechanisms exist in the literature.
Both species can be formed through barrierless reactions in ices
through NH +CO →HNCO and NH2+H2CO →NH2CHO +
H, as demonstrated experimentally (Fedoseev et al. 2015, 2016).
Alternatively, both species are formed through ion bombardment
of H2O:CH4:N2mixtures (Kaˇ
nuchová et al. 2016) or UV irradi-
ation of CO:NH3:CH3OH and/or HNCO mixtures (e.g. Demyk
et al. 1998; Raunier et al. 2004; Jones et al. 2011; Henderson
& Gudipati 2015). Quantitative gas-grain modeling under con-
ditions representative of IRAS16293 are needed to assess which
of these grain surface routes dominates.
Ultimately, the HNCO and NH2CHO deuterium fractiona-
tion level and pattern may also hold a clue to their formation
routes. A particularly interesting result is that the three singly
deuterated forms of formamide are found with similar abun-
dances in IRAS16293. Contrary to the -CH functional group
that is not affected by hydrogen isotope exchanges, the hy-
droxyl (-OH) and amine (-NH) groups are expected to estab-
lish hydrogen bonds and equilibrate with water (Faure et al.
2015). This mechanism was proposed to explain the different
CH3OD/CH3OH (∼1.8%) and CH2DOH/CH3OH (∼37%) ratios
derived in IRAS16293 (Parise et al. 2006), as the water deu-
terium fractionation of water in the upper layers of the grain
mantles where complex organic molecules form is about a few
percent (Coutens et al. 2012, 2013; Furuya et al. 2016). We do
not see such differences for formamide, for which all forms show
a deuterium fractionation similar to the CH3OD/CH3OH ratio
and water. The deuterium fractionation of methanol from the
PILS data needs to be investigated to know if the different deu-
terium fractionation ratios of the -CH and -OH groups are also
observed at small scales.
In conclusion, we present in this Letter the first detection of
the three singly deuterated forms of formamide and DNCO. The
similar deuteration of these species and their similar spatial dis-
tributions favours the formation of these two species on grain
surfaces. Further studies are, however, needed to rule out gas
phase routes. These detections illustrate the strength of ALMA,
and large spectral surveys such as PILS in particular, for the de-
tections of deuterated complex molecules. Determinations of the
deuterium fractionation for more complex molecules will help
to constrain their formation pathways. The search for deuterated
formamide in more sources is needed to reveal how variable the
deuteration of formamide is, and if the similarity of the abun-
dances of the three deuterated forms is common.
Acknowledgements. The authors thank Gleb Fedoseev and Harold Linnartz
for fruitful discussions. This paper makes use of the following ALMA data:
ADS/JAO.ALMA#2013.1.00278.S. ALMA is a partnership of ESO (represent-
ing its member states), NSF (USA) and NINS (Japan), together with NRC
(Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic
of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and
NAOJ. The work of AC was funded by a STFC grant. AC thanks the COST ac-
tion CM1401 ‘Our Astrochemical History’ for additional financial support. The
group of JKJ acknowledges support from a Lundbeck Foundation Group Leader
Fellowship as well as the European Research Council (ERC) under the European
Union’s Horizon 2020 research and innovation programme (grant agreement No
646908) through ERC Consolidator Grant “S4F”. Research at Centre for Star
and Planet Formation is funded by the Danish National Research Foundation.
The group of EvD acknowledges A-ERC grant 291141 CHEMPLAN.
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Article number, page 4 of 10

A. Coutens et al.: The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid
Appendix A: Spectroscopic data
A list of unblended and optically thin lines used in the analysis
is presented in Table A.1. The spectroscopic data for NH2CHO
3=0, NH2CHO 312=1, NH213 CHO, 15NH2CHO, NH2CH18O,
NH2CDO, cis-NHDCHO, trans-NHDCHO (Kurland & Bright
Wilson 1957; Kukolich & Nelson 1971; Hirota et al. 1974;
Gardner et al. 1980; Moskienko & Dyubko 1991; Vorob’eva &
Dyubko 1994; Blanco et al. 2006; Kryvda et al. 2009; Motiyenko
et al. 2012; Kutsenko et al. 2013) and HNCO (Kukolich & Nel-
son 1971; Hocking et al. 1975; Niedenhoffet al. 1995; Lapinov
et al. 2007) come from the CDMS database (Müller et al.
2001, 2005), while the data for DNCO, HN13CO, H15 NCO and
HNC18O (Hocking et al. 1975) are taken from the JPL database
(Pickett et al. 1998). It should be noted that there are significant
differences for the predicted frequencies of the main isotopo-
logue of NH2CHO between CDMS and JPL (>1 MHz). A bet-
ter agreement is found with the observations for the most recent
entry in CDMS. For some of the HNCO isotopologues, there is
a lack of published spectroscopic data at high frequencies. In
particular for H15NCO, the range of uncertainty for some of the
frequencies is quite high. As the HN13CO transitions appeared
all slightly shifted compared to the observations, we applied a
correction of +0.5 MHz to model the lines.
The column densities of the formamide isotopologues given
in Table 1 were corrected by a factor of 1.5 to take into account
the contribution of the vibrational states for an excitation tem-
perature of 300 K.
Article number, page 5 of 10

A&A proofs: manuscript no. NH2CHO_PILS_aa_v6
Table A.1. Detected lines of NH2CHO, HNCO and their isotopologues used in
the analysis(a) .
Species Transition Frequency Eup Aij gup
(MHz) (K) (s−1)
NH2CDO (17 0 17 – 16 0 16) 329995.2 145.6 2.64 ×10−3105
NH2CDO (16 9 7 – 15 9 6) 333363.6 308.9 1.87 ×10−399
NH2CDO (16 9 8 – 15 9 7) 333363.6 308.9 1.87 ×10−399
NH2CDO (16 7 10 – 15 7 9) 333696.6 240.7 2.22 ×10−399
NH2CDO (16 7 9 – 15 7 8) 333696.6 240.7 2.22 ×10−399
NH2CDO (16 4 13 – 15 4 12) 335234.9 170.5 2.61 ×10−399
NH2CDO (16 3 13 – 15 3 12) 342320.7 156.9 2.86 ×10−399
NH2CDO (17 1 16 – 16 1 15) 351988.3 158.1 3.18 ×10−3105
NH2CDO (17 10 7 – 16 10 6) 354151.5 366.4 2.15 ×10−3105
NH2CDO (17 10 8 – 16 10 7) 354151.5 366.4 2.15 ×10−3105
NH2CDO (17 9 8 – 16 9 7) 354257.0 325.9 2.37 ×10−3105
NH2CDO (17 9 9 – 16 9 8) 354257.0 325.9 2.37 ×10−3105
NH2CDO (17 8 10 – 16 8 9) 354416.0 289.6 2.56 ×10−3105
NH2CDO (17 8 9 – 16 8 8) 354416.0 289.6 2.56 ×10−3105
NH2CDO (17 7 11 – 16 7 10) 354661.3 257.7 2.74 ×10−3105
NH2CDO (17 7 10 – 16 7 9) 354661.3 257.7 2.74 ×10−3105
NH2CDO (17 5 12 – 16 5 11) 355800.2 206.7 3.04 ×10−3105
NH2CDO (17 4 13 – 16 4 12) 357938.5 187.8 3.20 ×10−3105
cis-NHDCHO (16 3 13 – 15 3 12) 331372.8 156.0 2.59 ×10−399
cis-NHDCHO (16 2 14 – 15 2 13) 337248.5 146.0 2.79 ×10−399
cis-NHDCHO (17 2 16 – 16 2 15) 340520.3 158.0 2.87 ×10−3105
cis-NHDCHO (18 1 18 – 17 1 17) 344878.9 160.8 3.02 ×10−3111
cis-NHDCHO (17 8 10 – 16 8 9) 346444.0 306.6 2.39 ×10−3105
cis-NHDCHO (17 8 9 – 16 8 8) 346444.0 306.6 2.39 ×10−3105
cis-NHDCHO (17 7 11 – 16 7 10) 346586.8 269.8 2.56 ×10−3105
cis-NHDCHO (17 7 10 – 16 7 9) 346586.8 269.8 2.56 ×10−3105
cis-NHDCHO (17 6 12 – 16 6 11) 346826.8 238.0 2.70 ×10−3105
cis-NHDCHO (17 6 11 – 16 6 10) 346827.5 238.0 2.70 ×10−3105
cis-NHDCHO (17 3 15 – 16 3 14) 347115.8 172.0 2.99 ×10−3105
cis-NHDCHO (17 5 12 – 16 5 11) 347268.9 211.1 2.83 ×10−3105
cis-NHDCHO (17 4 14 – 16 4 13) 347827.8 189.2 2.94 ×10−3105
cis-NHDCHO (17 3 14 – 16 3 13) 353047.5 173.0 3.15 ×10−3105
trans-NHDCHO (17 8 9 – 16 8 8) 333628.6 332.4 2.14 ×10−3105
trans-NHDCHO (17 8 10 – 16 8 9) 333628.6 332.4 2.14 ×10−3105
trans-NHDCHO (17 7 11 – 16 7 10) 333694.1 288.3 2.28 ×10−3105
trans-NHDCHO (17 7 10 – 16 7 9) 333694.1 288.3 2.28 ×10−3105
trans-NHDCHO (17 6 12 – 16 6 11) 333812.6 250.1 2.41 ×10−3105
trans-NHDCHO (17 6 11 – 16 6 10) 333812.7 250.1 2.41 ×10−3105
trans-NHDCHO (17 4 14 – 16 4 13) 334403.2 191.4 2.61 ×10−3105
trans-NHDCHO (18 1 18 – 17 1 17) 336945.3 157.3 2.82 ×10−3111
trans-NHDCHO (18 0 18 – 17 0 17) 338818.4 156.9 2.87 ×10−3111
trans-NHDCHO (17 1 16 – 16 1 15) 338878.8 150.6 2.86 ×10−3105
trans-NHDCHO (18 7 12 – 17 7 11) 353355.8 305.2 2.77 ×10−3111
trans-NHDCHO (18 7 11 – 17 7 10) 353355.8 305.2 2.77 ×10−3111
trans-NHDCHO (18 5 14 – 17 5 13) 353758.4 234.7 3.02 ×10−3111
trans-NHDCHO (18 3 16 – 17 3 15) 354028.8 187.8 3.19 ×10−3111
trans-NHDCHO (18 4 15 – 17 4 14) 354185.9 208.4 3.13 ×10−3111
NH213CHO (16 10 6 – 15 10 5) 339170.1 427.9 1.75 ×10−333
NH213CHO (16 10 7 – 15 10 6) 339170.1 427.9 1.75 ×10−333
NH213CHO (16 9 7 – 15 9 6) 339179.6 373.0 1.97 ×10−333
NH213CHO (16 9 8 – 15 9 7) 339179.6 373.0 1.97 ×10−333
NH213CHO (16 8 8 – 15 8 7) 339213.5 323.8 2.16 ×10−333
NH213CHO (16 8 9 – 15 8 8) 339213.5 323.8 2.16 ×10−333
NH213CHO (16 5 11 – 15 5 10) 339672.1 210.9 2.61 ×10−333
NH213CHO (16 4 13 – 15 4 12) 340090.4 184.9 2.72 ×10−333
Article number, page 6 of 10

A. Coutens et al.: The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid
Table A.1. continued.
Species Transition Frequency Eup Aij gup
(MHz) (K) (s−1)
NH213CHO (16 4 12 – 15 4 11) 340273.4 184.9 2.73 ×10−333
NH213CHO (17 1 17 – 16 1 16) 342156.0 151.5 2.95 ×10−335
NH213CHO (17 9 8 – 16 9 7) 360396.3 390.3 2.49 ×10−335
NH213CHO (17 9 9 – 16 9 8) 360396.3 390.3 2.49 ×10−335
NH213CHO (17 7 11 – 16 7 10) 360531.8 297.7 2.88 ×10−335
NH213CHO (17 7 10 – 16 7 9) 360531.8 297.7 2.88 ×10−335
NH213CHO (18 1 18 – 17 1 17) 361904.8 168.9 3.49 ×10−337
NH2CHO 3=0 (16 3 14 – 16 2 15) 331685.9 165.6 7.87 ×10−533
NH2CHO 3=0 (8 2 7 – 7 1 6) 334483.5 48.5 5.49 ×10−517
NH2CHO 3=0 (17 3 15 – 17 2 16) 336733.0 183.0 8.2 ×10−535
NH2CHO 3=0 (34 3 31 – 34 2 32) 342029.5 645.9 1.07 ×10−469
NH2CHO 3=0 (18 3 16 – 18 2 17) 342511.1 201.3 8.57 ×10−537
NH2CHO 3=0 (28 4 24 – 28 3 25) 344545.8 464.1 1.15 ×10−457
NH2CHO 3=0 (19 3 17 – 19 2 18) 349051.7 220.7 8.99 ×10−539
NH2CHO 3=0 (20 3 18 – 20 2 19) 356379.8 241.1 9.47 ×10−541
NH2CHO 3=0 (20 1 19 – 19 2 18) 359119.4 221.2 8.45 ×10−541
NH2CHO 312=1 (17 14 3 – 16 14 2) 360717.7 1144.3 1.12 ×10−335
NH2CHO 312=1 (17 14 4 – 16 14 3) 360717.7 1144.3 1.12 ×10−335
DNCO (17 1 17 18 – 16 1 16 17) 344629.4 172.9 5.92 ×10−437
DNCO (17 1 17 17 – 16 1 16 16) 344629.4 172.9 5.90 ×10−435
DNCO (17 1 17 16 – 16 1 16 15) 344629.4 172.9 5.90 ×10−433
DNCO (17 0 17 18 – 16 0 16 17) 346556.2 149.7 6.04 ×10−437
DNCO (17 0 17 17 – 16 0 16 16) 346556.2 149.7 6.02 ×10−435
DNCO (17 0 17 16 – 16 0 16 15) 346556.2 149.7 6.02 ×10−433
DNCO (17 5 12 18 – 16 5 11 17) 346714.9 750.6 5.53 ×10−437
DNCO (17 5 13 18 – 16 5 12 17) 346714.9 750.6 5.53 ×10−437
DNCO (17 5 13 16 – 16 5 12 15) 346714.9 750.6 5.50 ×10−433
DNCO (17 5 12 16 – 16 5 11 15) 346714.9 750.6 5.50 ×10−433
DNCO (17 5 13 17 – 16 5 12 16) 346714.9 750.6 5.51 ×10−435
DNCO (17 5 12 17 – 16 5 11 16) 346714.9 750.6 5.51 ×10−435
DNCO (17 1 16 18 – 16 1 15 17) 348599.7 174.6 6.13 ×10−437
DNCO (17 1 16 17 – 16 1 15 16) 348599.7 174.6 6.10 ×10−435
DNCO (17 1 16 16 – 16 1 15 15) 348599.7 174.6 6.10 ×10−433
HN13CO (15 2 13 16 – 14 2 12 15) 329594.5 299.2 5.08 ×10−433
HN13CO (15 2 13 14 – 14 2 12 13) 329594.5 299.2 5.06 ×10−429
HN13CO (15 2 13 15 – 14 2 12 14) 329594.5 299.2 5.06 ×10−431
HN13CO (15 0 15 16 – 14 0 14 15) 329673.4 126.6 5.18 ×10−433
HN13CO (15 0 15 15 – 14 0 14 14) 329673.4 126.6 5.16 ×10−431
HN13CO (15 0 15 14 – 14 0 14 13) 329673.4 126.6 5.15 ×10−429
HN13CO (15 1 14 16 – 14 1 13 15) 330860.2 170.2 5.21 ×10−433
HN13CO (15 1 14 14 – 14 1 13 13) 330860.2 170.2 5.19 ×10−429
HN13CO (15 1 14 15 – 14 1 13 14) 330860.2 170.2 5.19 ×10−431
HN13CO (16 1 16 17 – 15 1 15 16) 350340.3 186.1 6.20 ×10−435
HN13CO (16 1 16 16 – 15 1 15 15) 350340.3 186.1 6.18 ×10−433
HN13CO (16 1 16 15 – 15 1 15 14) 350340.3 186.1 6.18 ×10−431
HN13CO (16 3 14 17 – 15 3 13 16) 351427.6 531.9 6.07 ×10−435
HN13CO (16 3 14 15 – 15 3 13 14) 351427.6 531.9 6.04 ×10−431
HN13CO (16 3 14 16 – 15 3 13 15) 351427.7 531.9 6.04 ×10−433
HN13CO (16 3 13 17 – 15 3 12 16) 351427.7 531.9 6.07 ×10−435
HN13CO (16 3 13 15 – 15 3 12 14) 351427.7 531.9 6.04 ×10−431
HN13CO (16 3 13 16 – 15 3 12 15) 351427.7 531.9 6.04 ×10−433
HN13CO (16 2 15 17 – 15 2 14 16) 351548.3 316.1 6.19 ×10−435
HN13CO (16 2 15 15 – 15 2 14 14) 351548.3 316.1 6.17 ×10−431
HN13CO (16 2 15 16 – 15 2 14 15) 351548.3 316.1 6.17 ×10−433
HN13CO (16 2 14 17 – 15 2 13 16) 351561.8 316.1 6.19 ×10−435
HN13CO (16 2 14 15 – 15 2 13 14) 351561.8 316.1 6.17 ×10−431
HN13CO (16 2 14 16 – 15 2 13 15) 351561.8 316.1 6.17 ×10−433
Article number, page 7 of 10

A&A proofs: manuscript no. NH2CHO_PILS_aa_v6
Table A.1. continued.
Species Transition Frequency Eup Aij gup
(MHz) (K) (s−1)
HN13CO (16 2 14 17 – 15 2 13 16) 351561.8 316.1 6.19 ×10−435
HN13CO (16 2 14 15 – 15 2 13 14) 351561.8 316.1 6.17 ×10−431
HN13CO (16 2 14 16 – 15 2 13 15) 351561.8 316.1 6.17 ×10−433
HN13CO (16 0 16 17 – 15 0 15 16) 351642.9 143.5 6.30 ×10−435
HN13CO (16 0 16 16 – 15 0 15 15) 351642.9 143.5 6.27 ×10−433
HN13CO (16 0 16 15 – 15 0 15 14) 351642.9 143.5 6.27 ×10−431
Notes. (a)This list only includes optically thin and unblended lines.
Appendix B: Additional figures
329.990 329.995 330.000
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
(Jy/beam)
333.360 333.365
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
333.695 333.700
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
335.230 335.235 335.240
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
342.320 342.325
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
351.985 351.990
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
354.150 354.155
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
(Jy/beam)
354.255 354.260
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
354.415 354.420
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
354.660 354.665
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
355.795 355.800 355.805
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
357.935 357.940
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
N = 1.20000e+14 cm-2, Tex = 300.000
Fig. B.1. Black: Detected lines of NH2CDO. Red: Best-fit model for Tex=300 K.
331.370 331.375
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
(Jy/beam)
337.245 337.250
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
340.515 340.520 340.525
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
344.875 344.880
Frequency (GHz)
-0.1
0.0
0.1
0.2
0.3
0.4
346.440 346.445
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
346.585 346.590
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
346.825 346.830
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
(Jy/beam)
347.115 347.120
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
347.265 347.270
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
347.825 347.830
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
353.045 353.050
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
N = 1.20000e+14 cm-2, Tex = 300.000
Fig. B.2. Black: Detected lines of cis-NHDCHO. Red: Best-fit model for Tex=300 K.
Article number, page 8 of 10

A. Coutens et al.: The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid
333.625 333.630
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
(Jy/beam)
333.690 333.695
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
333.810 333.815
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
334.400 334.405
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
336.940 336.945 336.950
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
338.815 338.820
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
338.875 338.880
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
(Jy/beam)
353.350 353.355 353.360
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
353.755 353.760
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
354.025 354.030
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
354.185 354.190
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
N = 1.00000e+14 cm-2, Tex = 300.000
Fig. B.3. Black: Detected lines of trans-NHDCHO. Red: Best-fit model for Tex=300 K.
339.165 339.170 339.175
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
(Jy/beam)
339.175 339.180 339.185
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
339.210 339.215
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
339.670 339.675
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
340.085 340.090 340.095
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
340.270 340.275
Frequency (GHz)
-0.02
0.00
0.02
0.04
342.155 342.160
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
(Jy/beam)
360.395 360.400
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
360.530 360.535
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
361.900 361.905 361.910
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
N = 1.00000e+14 cm-2, Tex = 300.000
Fig. B.4. Black: Detected lines of NH213CHO. Red: Best-fit model for Tex=300 K. Green: Best-fit model for Tex=100 K.
344.625 344.630 344.635
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
(Jy/beam)
346.555 346.560
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0.12
346.710 346.715 346.720
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
348.595 348.600 348.605
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
N = 3.00000e+14 cm-2, Tex = 300.000
Fig. B.5. Black: Detected lines of DNCO. Red: Best-fit model for Tex=300 K.
329.590 329.595 329.600
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
(Jy/beam)
329.670 329.675
Frequency (GHz)
-0.05
0.00
0.05
0.10
0.15
330.860 330.865
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
350.340 350.345
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
351.425 351.430
Frequency (GHz)
-0.1
0.0
0.1
0.2
0.3
351.545 351.550
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
351.560 351.565
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
(Jy/beam)
351.640 351.645
Frequency (GHz)
-0.05
0.00
0.05
0.10
0.15
N = 4.00000e+14 cm-2, Tex = 300.000
Fig. B.6. Black: Detected lines of HN13CO. Red: Best-fit model for Tex=300 K. Green: Best-fit model for Tex=100 K.
Article number, page 9 of 10

A&A proofs: manuscript no. NH2CHO_PILS_aa_v6
331.685 331.690
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
(Jy/beam)
334.480 334.485
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
336.730 336.735
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
342.025 342.030 342.035
Frequency (GHz)
-0.02
-0.01
0.00
0.01
0.02
0.03
342.510 342.515
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
344.545 344.550
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
349.050 349.055
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
(Jy/beam)
356.375 356.380 356.385
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
359.115 359.120 359.125
Frequency (GHz)
-0.02
0.00
0.02
0.04
N = 6.00000e+15 cm-2, Tex = 300.000
Fig. B.7. Black: Lines of NH2CHO 3=0 with the lowest opacities. Red: Model based on the analysis of the NH213CHO lines and a 12C/13 C ratio
equal to 68.
360.715 360.720
Frequency (GHz)
-0.02
0.00
0.02
0.04
0.06
(Jy/beam)
N = 6.00000e+15 cm-2, Tex = 300.000
Fig. B.8. Black: Line of NH2CHO 312=1 with the lowest opacity. Red: Model based on the analysis of the NH213CHO lines and a 12C/13 C ratio
equal to 68.
Article number, page 10 of 10