Chemical composition of comets C/2021 A1 (Leonard) and C/2022 E3 (ZTF) from radio spectroscopy and the abundance of HCOOH and HNCO in comets

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Volume 690 (October 2024)

A&A, 690 (2024) A271

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Table B.5

Production from a distributed source based on offset pointings on comet C/2021 A1 (Leonard).

UT (mm/dd.d)	Molecule	Freq. range (GHz)	lines ^(a)	off. ^(b) (″)	Line intensity (K km s⁻¹)	L_p^(c) (km)	Q_p^(d) (×10²⁵ molecules s⁻¹)	χ²
12/12.40	HCN	265.886	1	1.1	1.714 ± 0.050	0	2.9 ± 0.1	15.2
				4.8	1.274 ± 0.091	$560_{- 220}^{+ 330}$ $\[560_{-220}^{+330}\]$	3.9 ± 0.1	7.5
				8.4	0.977 ± 0.092
				11.0	1.113 ± 0.125
12/13.40	HCN	265.886	1	0.4	2.022 ± 0.045	0	3.4 ± 0.1	4.5
				10.0	0.939 ± 0.072	240 ± 100	3.9 ± 0.1	0.1
				14.1	0.686 ± 0.067

12/10.6	HNC	271.981	1	1.7	0.121 ± 0.012	0 ± 700	0.19 ± 0.02	2.7
12/11.0				4.7	0.011 ± 0.049	1000	0.30 ± 0.03	4.1
12/11.0				10.3	0.050 ± 0.027

12/12.5	CS	244.936	1	1.8	0.344 ± 0.013	0	2.2 ± 0.1	3.7
				3.8	0.274 ± 0.079	260	2.6 ± 0.1	2.2
				8.2	0.242 ± 0.038	$500_{- 390}^{+ 580}$ $\[500_{-390}^{+580}\]$	3.0 ± 0.1	1.9
				11.8	0.105 ± 0.043	1000	3.8 ± 0.1	2.7
12/13.6	CS	244.936	1	1.1	0.357 ± 0.020	0	2.5 ± 0.1	27.6
				8.7	0.170 ± 0.079	260	2.9 ± 0.1	20.0
				10.4	0.271 ± 0.039	1000	4.2 ± 0.2	8.3
		146.969	1	1.7	0.143 ± 0.011	$7000_{- 430}^{+ 36000}$ $\[7000_{-430}^{+36000}\]$	12.6 ± 0.5	2.4
				10.3	0.109 ± 0.031

12/12.6	H₂CO	211,226	2	0.9	0.185 ± 0.012	0	2.2 ± 0.1	4.8
				10.2	0.078 ± 0.022	$1500_{- 970}^{+ 3700}$ $\[1500_{-970}^{+3700}\]$	10.2 ± 0.6	1.4
				14.7	0.098 ± 0.043	4000	18.8 ± 1.2	2.0

12/11.1	HNCO	153.865	1	1.9	0.040 ± 0.006	0	3.2 ± 0.3	13.5
12/11.8				10.3	0.036 ± 0.021	2000	7.1 ± 0.6	4.1
12/12.8		219–264	3	1.4	0.050 ± 0.005	10000	23.0 ± 1.9	1.8
12/12.9		242,264	2	9.9	0.030 ± 0.014

12/12.7	HCOOH	215–268	13^(e)	1.5	0.0166 ± 0.0024	0	7.3 ± 0.9	4.9
			10	10.1	0.0168 ± 0.0074	2000	19.4 ± 2.5	2.7

12/12.2	NH₂CHO	211–267	11	1.4	0.0321 ± 0.0031	0 ± 400	10.8 ± 1.1
12/12.7		K_a < 3	11	10.2	0.0081 ± 0.0079

Notes. ^(a)Number of lines used or averaged. ^(b)Mean pointing offset. ^(c)Parent scale length in km. The value with uncertainty (or lower limit) is the one obtained from the χ² minimisation. ^(d)Production rates from nuclear or distributed source with given parent scale length.

^(e)The χ² fitting was computed using all individual lines intensities separately, not their average. ^(f)This χ² for HCN(3–2) includes an additional 10% calibration uncertainty. Without, χ² is about two orders of magnitude but leads to the same L_p.

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