A Survey of HNCO and CH3NCO in Molecular
Clouds
DeWayne T. Halfen and Lucy M. Ziurys
Department of Chemistry and Biochemistry
Department of Astronomy
Steward Observatory
University of Arizona
Arizona
Radio
Observatory
June 22, 2016
Detection of HNCO and CH3NCO in Comet 67P
• In Nov. 2014 Philae landed on comet 67P
• COSAC mass spectrometer detected a number of organic
species in the gas (Goesmann et al. Science 2015)
• Included HNCO and CH3NCO
• Also suggested that isocyanates could play a role in peptide
formation in comets
Comet 67P
Philae
CH3NCO
0.09
0.06
Detection of CH3NCO in
Sgr B2(N)
0.03
Sgr B2(N)
80,8  70,7 A
69353.9 MHz
NS
C3S
U
U
0.00
90,9  80,8 A
78017.9 MHz
0.09
CH3CH2OH +
0.06
13
CH3OH
HCOOCH3 +
(CH2OH)2
CH3CH2OH
CH3CH2OH
0.03
0.00
• Identified the spectrum of CH3NCO
in Sgr B2(N) (Halfen et al. 2015)
0.09 100,10  90,9 A,E
SO2
HCO
86680.2 MHz
0.06 86686.6 MHz
(CH2OH)2
HCO
C3S
0.03
0.00
0.09
0.06
110,11  100,10 A
95341.1 MHz
• Detected 17 uncontaminated lines
13
13
U
CH2CH CN
CH3OH
SO2
0.03
120,12  110,11 A
103999.9 MHz
CH3CH2OH
0.09
CH2CH CN CH3CH2OH
0.00
0.06
90,9  80,8 E
78087.7 MHz
U
U
0.03
CH3CH2OH
0.09
CH3CH2OH +
HCOOCH3
U
CH3CH2OH +
13
CH3OH
CH3CH2OH
U
0.00
0.09 81,8  71,7 A
0.06
70009.2 MHz
0.03
U
U
0.00
0.09
0.06
0.03
91,8  81,7 A
77347.4 MHz
CH3CH2CN
2015)
– Combined fit to Koput and new data,
and identified in Sgr B2(N) survey
spectrum at 3 mm
U
0.00
0.06
• Based on previous laboratory work
by Koput (1986) and new FTmmW
data from 60 – 88 GHz (Halfen et al.
CH2NH
+U
CHOCH2OH
U
CH3CH2CN
TR* (K)
0.03
CH2CHCN
U
CH3CH2OH
CH3CONH2
0.00
(Halfen, Ilyushin, & Ziurys ApJL 2015)
-96
-16
64
VLSR (km/s)
144
224
Survey of HNCO and CH3NCO in Molecular Clouds
• Seek to determine if HNCO and CH3NCO are linked
chemically
• Performed a survey of each species in several giant molecular
clouds
• G34.3, W51M, Orion-KL, Sgr B2(2N), G10.47, and G31.41
• Is Sgr B2(N) unique?
• How widespread is CH3NCO?
HNCO and CH3NCO Observations
• Used the ARO ALMA Prototype Antenna (APA) 12 m at 3 mm
and Submillimeter Telescope (SMT) 10 m at 1 mm
APA 12 m
SMT 10m
KP 12 m
Arizona
Radio
Observatory
• Searched for 4 rotational transitions of HNCO in Ka = 0 and 2,
and 4 lines of CH3NCO in Ka = 0 A and E
• Observed each species in six giant molecular clouds
• Each transition observed for 2 – 20 hours
Species
HNCO
CH3NCO
Transition
J′Ka,Kc  J″Ka,Kc
42,3  32,2
42,2  32,1
40,4  30,3
52,4  42,3
52,3  42,2
50,5  40,4
102,9  92,8
100,8  92,7
100,10  90,9
122,11  112,10
122,10  102,9
120,12  100,10
100,10  90,9
100,10  90,9
110,11  100,10
120,12  110,11
Sym
m
A
E
A
A
0
1
0
0
Frequency
(MHz)
87898.425
87898.628
87925.237
109872.337
109872.765
109905.749
219733.850
219737.193
219798.274
263672.912
263678.709
263748.625
86680.190
86686.556
95340.443
103998.481
HNCO
0.45
G34.3
JK ,K = 40,4
a
c
CH3NCO
30,3
0.012
JK ,K = 100,10
0.008
E
a
0.30
0.15
0.004
0.00
0.45
JK ,K = 50,5
a
0.30
c
0.00
0.45
JK ,K = 100,10
a
0.30
c
TA* (K)
TA* (K)
JK ,K = 110,11
0.012
0.15
90,9
90,9
HCO
A
HCO
C3S
0.000
40,4
c
G34.3
a
c
100,10 A
CH2CHCN
0.008
0.004
0.000
0.15
HCOOCH3
JK ,K = 120,12
0.012
0.00
0.45
JK ,K = 120,12
HCCCN
a
0.30
c
110,11
a
c
110,11 A
CH3CH2OH
0.008
0.004
0.15
0.000
0.00
8
33
58
83
108
8
33
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
58
83
-1
VLSR (km s )
108
HNCO
W51M
JK ,K = 40,4
0.6
a
c
CH3NCO
0.045
30,3
JK ,K = 100,10
a c
E
0.030
0.4
W51M
90,9
HCO
A
0.2
0.015
0.0
JK ,K = 50,5
0.6
a
c
40,4
0.000
0.4
JK ,K = 110,11
0.016
0.2
TA* (K)
TA* (K)
HCO
C3S
0.0
JK ,K = 100,10
0.6
a
c
90,9
0.4
a
c
100,10 A
CH2CHCN
0.008
0.000
HCOOCH3
0.2
0.016 CH3CH2OH
0.0
JK ,K = 120,12
HCCCN
0.6
a
c
110,11
JK ,K = 120,12
a
c
110,11 A
0.008
0.4
0.000
0.2
0.0
8
33
58
83
108
8
33
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
58
83
-1
VLSR (km s )
108
HNCO
9.0
Sgr B2(2N)
JK ,K = 40,4
a
c
CH3NCO
30,3
JK ,K = 100,10
0.060
a
6.0
0.030
0.0
9.0
0.015
JK ,K = 50,5
a
6.0
c
40,4
HCO
C3S
a
TA* (K)
TA* (K)
c
90,9
1.0
c
100,10 A
CH2CHCN
0.045
0.030
U
0.015
0.000
0.5
0.0
0.6
E
JK ,K = 110,11
0.060
a
HCO
0.000
3.0
JK ,K = 100,10
90,9
A
0.045
3.0
0.0
1.5
c
Sgr B2(2N)
JK ,K = 120,12
0.060
a
JK ,K = 120,12
a
0.4
c
c
110,11 A
CH2CH13CN
0.045
110,11
0.030
0.2
0.015
0.0
0.000
18
43
68
93
118
18
43
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
68
93
-1
VLSR (km s )
118
HNCO
JK ,K = 40,4
a
c
CH3NCO
30,3
JK ,K = 100,10
0.02
a
0.01
JK ,K = 50,5
a
0.6
c
40,4
1.5
90,9
JK ,K = 120,12
HCCCN
a
3.0
c
110,11
100,10 A
0.02
U
0.01
0.00
0.03
HCOOCH3
0.0
4.5
c
SO2
0.02
0.01
JK ,K = 120,12
CH3CH2OH
3.0
c
TA* (K)
TA* (K)
a
a
A
HCO
C3S
JK ,K = 110,11
JK ,K = 100,10
HCO
0.00
0.03
0.3
0.0
4.5
90,9
c
E
0.2
0.0
0.9
Orion-KL
CH2CHCN
0.4
Orion-KL
a
c
110,11 A
1.5
0.00
0.0
-41
-16
9
34
59
-41
-16
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
9
34
-1
VLSR (km s )
59
HNCO
0.6
G10.47
0.03
JK ,K = 40,4
a
c
30,3
JK ,K = 100,10
0.4
0.02
0.2
0.01
0.0
0.6
JK ,K = 50,5
c
a
c
c
TA* (K)
a
0.4
90,9
HCO
A
0.03
JK ,K = 110,11
JK ,K = 100,10
G10.47
0.00
40,4
0.2
TA* (K)
a
E
0.4
0.0
0.6
CH3NCO
90,9
a
0.02
c
100,10 A
CH2CHCN
0.01
0.00
0.2
0.03
0.0
0.6
0.02
JK ,K = 120,12
JK ,K = 120,12
a
0.4
c
110,11
a
c
110,11 A
CH3CH2OH
0.01
0.2
0.00
0.0
18
43
68
93
118
18
43
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
68
93
-1
VLSR (km s )
118
HNCO
0.30
G31.41
JK ,K = 40,4
a
c
0.024
30,3
0.016
CH3NCO
G31.41
JK ,K = 100,10
a c
E
90,9
JK ,K = 110,11
100,10 A
JK ,K = 120,12
110,11 A
HCO
A
0.15
0.008
0.00
0.30
JK ,K = 50,5
a
c
0.000
40,4
0.024
TA* (K)
0.15
a
0.016
c
CH2CHCN
0.00
0.30
JK ,K = 100,10
a
c
0.008
90,9
0.000
0.15
0.024
0.00
a
JK ,K = 120,12
0.30
a
c
110,11
0.016
c
CH3CH2OH
0.008
0.15
0.000
0.00
48
73
98
123
148
48
73
-1
VLSR (km s )
• HNCO and CH3NCO detected in each source
98
123
-1
VLSR (km s )
148
13.0
Rotational Temperature Diagram for HNCO
G34.3
log (3kW/8p3nSm2)
12.0
Trot = 33 1 K
Ntot = 5.8 0.2 x 1013 cm-2
11.0
Trot = 118 15 K
Ntot = 6.9 1.5 x 1013 cm-2
10.0
9.0
0
50
100
150
200
250
Eu (K)
• HNCO has two temperature components in G34.3, W51M,
G31.41, G10.47 – only in cold gas in Sgr B2(2N)
14
Rotational Temperature Diagram for HNCO
VLSR = 62 km s-1
Trot = 13.5 0.2 K
Ntot = 1.3 0.1 x 1015 cm-2
log (3kW/8p3nSm2)
13
SgrB2(2N)
B2(2N)
Sgr
12
VLSR = 73 km s-1
Trot = 15.3 0.3 K
Ntot = 8.6 0.6 x 1014 cm-2
11
10
0
50
100
150
200
250
Eu (K)
• HNCO has two temperature components in G34.3, W51M,
G31.41, G10.47 – only in cold gas in Sgr B2(2N)
13.5
Rotational Temperature Diagram for HNCO
log (3kW/8p3nSm2)
12.5
Trot = 205 24 K
Ntot = 6.3 0.6 x 1014 cm-2
Orion-KL
11.5
10.5
9.5
0
50
100
150
200
250
Eu (K)
• HNCO mostly in hot core in Orion-KL, with some emission in
plateau and ridge – needs more analysis
11.0
Rotational Temperature Diagram for CH3NCO
log (3kW/8p3nWstSm2)
10.5
G31.41
Trot = 28 10 K
Ntot = 4.9 1.7 x 1012 cm-2
10.0
9.5
9.0
8.5
8.0
0
5
10
15
20
25
30
35
Eu (K)
• CH3NCO found in cold gas in each source
• Sgr B2(2N) has two velocity components
40
45
50
11.5
Rotational Temperature Diagram for CH3NCO
11.0
log (3kW/8p3nWstSm2)
Sgr B2(2N)
10.5
VLSR = 73 km s-1
Trot = 12 4 K
Ntot = 2.0 1.6 x 1013 cm-2
10.0
VLSR = 62 km s-1
Trot = 8.7 1.6 K
Ntot = 2.8 1.7 x 1013 cm-2
9.5
9.0
0
5
10
15
20
25
30
35
40
Eu (K)
• CH3NCO only found in cold gas in each source
• Sgr B2(2N) has two velocity components
45
50
Column Densities of HNCO and CH3NCO
HNCO
Source
Sgr B2(N)
(62 km/s)
Sgr B2(N)
(73 km/s)
W51M
G34.3
Orion-KL
Sgr B2(2N)
(62 km/s)
Sgr B2(2N)
(73 km/s)
G31.41
G10.47
CH3NCO
Ntot (cm-2)
Trot (K)
Ntot (cm-2)
Trot (K)
Ntot (cm-2)
Trot (K)
5.2 x 1014
22
9.3 x 1014
136
2.3 x 1013
24
8.1 x 1014
15
1.1 x 1014
118
1.5 x 1013
28
1.6 x 1014
5.8 x 1013
--
52
33
--
2.7 x 1014
6.9 x 1013
6.3 x 1014
138
118
205
7.7 x 1012
2.8 x 1012
4.7 x 1012
10
26
27
1.3 x 1015
14
--
--
2.8x 1013
9
8.6 x 1014
15
--
--
2.0 x 1013
12
4.5 x 1013
1.2 x 1014
36
43
9.5 x 1013
2.8 x 1014
104
145
4.9 x 1012
4.0 x 1012
28
25
14.0
Comparison between Column Densities of HNCO and CH3NCO
Log(Ntot) for CH3NCO
13.5
y = 0.6295x + 3.9106
R² = 0.8721
13.0
12.5
12.0
13.0
13.5
14.0
14.5
Log(Ntot) for HNCO
15.0
15.5
• Abundances of HNCO and
CH3NCO quite correlated
• Ratio of HNCO in cold
component of each source to
CH3NCO between 9 – 54
• Suggests that HNCO and
CH3NCO are linked
chemically
• HNCO could be parent
species of CH3NCO in
neutral-neutral reaction
CH3∙ + HNCO → CH3NCO + H∙
• More work needs to be done
to confirm this
Ratio of HNCO/CH3NCO
Source
Sgr B2(N)
(62 km/s)
Sgr B2(N)
(73 km/s)
W51M
G34.3
Orion-KL
Sgr B2(2N)
(62 km/s)
Sgr B2(2N)
(73 km/s)
G31.41
G10.47
Ratio
23
54
21
21
-46
43
9.2
30
Conclusions
• CH3NCO widespread in molecular clouds across the Galaxy
• CH3NCO found in cold gas in each source, HNCO in cold and
warm gas
• Similar ratio between HNCO and CH3NCO in each source
• HNCO likely parent species of CH3NCO
• CH3NCO highly reactive and could lead to peptides on comet
surfaces
Acknowledgements
•
•
•
•
•
•
Prof. Lucy Ziurys
Julie Anderson
Debbie Schmidt
John Keogh
Kyle Kilchenstein
Mark Burton
• NASA NExSS program