Appendix C
International Astronomical Union Spectral Lines of Most Importance Below 300 GHz
At each triennial meeting of the General Assembly, the International Astronomical Union (IAU) carefully reviews the list of astrophysically most important spectral lines that it maintains. The IAU expresses the need to protect these frequency bands from in-band, band-edge, and harmonic emissions, especially from spaceborne transmitters.
In preparation for World Radiocommunication Conference 2000, which revised the allocations above 71 GHz, a millimeter-wavelength working group of the Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science examined all then-known transitions in the millimeter and submillimeter wavebands. The working group selected a limited number of the astrophysically most important spectral lines to supplement the earlier lists, such as those produced by the IAU, to be used in allocating frequency bands to the Radio Astronomy Service. Spectral lines below 300 GHz are listed in Table C.1. (Unless otherwise noted, the band limits are Doppler-shifted frequencies corresponding to radial velocities of ± 300 km/s, consistent with line radiation occurring in the Galaxy. These data and further information can be found on the Web site of the European Science Foundation’s Committee on Radio Astronomy Frequencies at http://www.astron.nl/craf/iaulist.htm.)
TABLE C.1 The Most Important Spectral Lines Below 275 GHz
Substance |
Formula |
Frequency (GHz) |
Suggested Minimum Band (GHz) |
Band Allocation Status1 |
Deuterium |
D I |
0.327384 |
0.327-0.3277 |
P |
Hydrogen |
HI |
1.370-1.427 |
S 1.33-1.40 |
|
|
|
|
|
P 1.40-1.427 |
Hydroxyl radical |
OH |
1.6068-1.6138 |
P 1.6106-1.6138 |
|
|
|
1.6654026 |
1.6598-1.6671 |
P 1.66-1.67 |
|
|
1.6673596 |
1.6618-1.6690 |
|
Hydroxyl radical |
OH |
1.7148-1.7222 |
S 1.7188-1.7222 |
|
Methyladyne |
CH |
3.2424-3.2671 |
S 3.260-3.267 |
|
|
|
3.3244-3.3388 |
S 3.332-3.339 |
|
|
|
3.3380-3.3525 |
S 3.3458-3.3525 |
|
Formaldehyde |
H2CO |
4.8136-4.8345 |
S 4.8-4.9 |
|
Methanol |
CH3OH |
6.6618-6.6752 |
S 6.650-6.6752 |
|
Helium |
3He+ |
8.665650 |
8.6570-8.6743 |
|
Methanol |
CH3OH |
12.17-12.19 |
|
|
Formaldehyde |
H2CO |
14.44-14.50 |
S 14.47-14.50 |
|
Cyclopropenylidene |
C3H2 |
18.28-18.36 |
|
|
Water vapor |
H2O |
22.16-22.26 |
F 22.01-22.21 |
|
|
|
|
|
P 22.21-22.50 |
Dicarbon monosulphide |
CCS |
22.344 |
22.32-22.37 |
|
Ammonia |
NH3 |
23.6946 |
23.61-23.89 |
P 23.60-24.00 |
|
|
23.7236 |
23.8706 |
|
Sulphur monoxide |
SiO |
30.002 |
29.97-30.03 |
|
Methanol |
CH3OH |
36.169 |
36.13-36.21 |
P9 36-37 |
Silicon monoxide |
SiO |
42.519 |
42.47-42.57 |
|
|
|
42.821 |
42.78-42.86 |
F 42.77-42.87 |
|
|
43.122 |
43.08-43.17 |
F 43.07-43.17 |
|
|
43.424 |
43.38-43.47 |
F 43.37-43.37 |
Dicarbon monosulphide |
CCS |
45.379 |
45.33-45.42 |
|
Carbon monosulphide |
CS |
48.991 |
48.94-49.04 |
P 48.94-49.04 |
Oxygen |
O2 |
61.1 |
56.21-63.06 |
P10 58.2-59.0 |
Deuterated water |
HDO |
80.578 |
80.50-80.66 |
|
Cyclopropenylidene |
C3H2 |
85.339 |
85.05-85.42 |
|
Silicon monoxide |
SiO |
86.243 |
86.16-86.33 |
P |
Formylium |
H13CO+ |
86.754 |
86.67-86.84 |
P |
Silicon monoxide |
SiO |
86.847 |
86.76-86.93 |
P |
Ethynyl radical |
C2H |
87.30011 |
87.21-87.39 |
P |
Substance |
Formula |
Frequency (GHz) |
Suggested Minimum Band (GHz) |
Band Allocation Status1 |
Hydrogen cyanide |
HCN |
88.6326 |
88.34-88.72 |
P |
Formylium |
HCO++ |
89.1896 |
88.89-89.28 |
P |
Hydrogen isocyanide |
HNC |
90.664 |
90.57-90.75 |
P |
Diazenylium |
N2H+ |
93.174 |
93.08-93.27 |
|
Carbon monosulphide |
CS |
97.9816 |
97.65-98.08 |
|
Sulfur monoxide |
SO |
99.300 |
99.20-99.40 |
|
Methyl acetylene |
CH3CCH |
102.5 |
102.39-102.60 |
|
Methanol |
CH3OH |
107.014 |
106.91-107.12 |
|
Carbon monoxide |
C18O |
109.782 |
109.67-109.89 |
P |
Carbon monoxide |
13CO |
110.2016 |
110.83-110.31 |
P |
Carbon monoxide |
C17O |
112.3598 |
112.25-112.47 |
P |
Cyano radical |
CN |
113.500 |
113.39-113.61 |
P |
Carbon monoxide |
CO |
115.2716 |
114.88-115.39 |
P |
Oxygen |
O2 |
118.750 |
118.63-118.87 |
P6 116-126 |
Formaldehyde |
H213CO |
137.31-137.59 |
|
|
Formaldehyde |
H2CO |
140.840 |
140.69-140.98 |
P |
Carbon monosulphide |
CS |
146.969 |
146.48-147.12 |
P 146.82-147.12 |
Nitric oxide |
NO |
150.4 |
149.95-150.85 |
S 150-151 |
Methanol |
CH3OH |
156.602 |
156.45-156.76 |
|
Water vapor |
H2O |
183.310 |
183.13-183.49 |
|
Carbon monoxide |
C18O |
219.560 |
219.34-219.78 |
P |
Carbon monoxide |
13CO |
220.3996 |
219.67-220.62 |
P |
Cyano radical |
CN |
226.600 |
226.37-226.83 |
P |
Cyano radical |
CN |
226.800 |
226.57-227.03 |
P |
Carbon monoxide |
CO |
230.5386 |
229.77-230.77 |
P |
Carbon monosulphide |
CS |
244.9538 |
244.14-245.20 |
|
Nitric oxide |
NO |
250.6 |
250.35-250.85 |
P |
Ethynyl radical |
C2H |
262.000 |
261.74-262.26 |
|
Hydrogen cyanide |
HCN |
265.886 |
265.00-266.15 |
|
Formylium |
HCO++ |
267.557 |
266.66-267.82 |
|
Hydrogen isocyanide |
HNC |
271.981 |
271.71-272.25 |
|
Carbon monosulphide |
13CS |
277.455 |
277.18-277.73 |
|
Diazenylium |
N2H+ |
279.511 |
279.23-279.79 |
|
Carbon monosulphide |
C34S |
289.209 |
288.92-289.50 |
|
Sodium hydride |
NaH |
289.860 |
289.57-290.15 |
|
Carbon monosulphide |
CS |
293.912 |
292.93-294.21 |
|
NOTE: Definitions of abbreviations for the various services referred to in the footnotes to this table are provided in Appendix I. 1P: primary allocation, S: secondary allocation, F: protection by footnote. 2An extension to lower frequencies of the allocation of 1400-1427 MHz is required to allow for the Doppler shifts for HI observed in distant galaxies. 3For passive EESS and SRS, along with FS and MS. 4The current international allocation is not primary and/or does not meet bandwidth requirements. See the ITU-R Radio Regulations for more detailed information. 5Because these line frequencies are also being used for observing other galaxies, the listed bandwidths include Doppler shifts corresponding to radial velocities of up to 1000 km/s. It should be noted that HI has been observed at frequencies redshifted to 500 MHz, while some lines of the most abundant molecules have been detected in galaxies with velocities up to 50,000 km/s, corresponding to a frequency reduction of up to 17%. 6For passive EESS and SRS, along with FS and MS. 7This line is not mentioned in Article 8 of the ITU-R Radio Regulations. 8For passive EESS and SRS, along with FS and MS. 9For passive EESS and SRS, with secondary allocations to FS and MS. 10United States only. 11There are six closely spaced lines associated with this molecule at this frequency. The listed band is wide enough to permit observations of all six lines. SOURCE: Data and further information can be found at the Web site of the European Science Foundation’s Committee on Radio Astronomy Frequencies at http://www.astron.nl/craf/iaulist.htm, accessed October 26, 2005. |