JOYS+: The link between the ice and gas of complex organic molecules - Comparing JWST and ALMA data of two low-mass protostars

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Volume 690 (October 2024)

A&A, 690 (2024) A205

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Table I.1

Fitting statistics of the scaling factors^† of lab spectra. The best-fit values, standard errors (σ_a) and relative errors (a/σ_a) are listed for least-squares and MCMC fittings. All the 12 candidate species were considered in the least-squares fitting, and nine of them were included in the MCMC fitting.

Ice mixture				Least-squares			MCMC

Constituents	Ratio	T (K)	Fit range ^a	Best-fit a	σ_a	a/σ_a (%)	Best-fit a	σ	a/σ_a (%)
CH₄:H₂O	1:100	13	0–5	3.61	0.03	0.8	3.66	0.27	7.3
SO₂:CH₃OH	1:1	10	0–1.0	4.2×10⁻⁷	0.56	1.3×10⁸	−	−	−
OCN⁻	−	15	0–8.0	6.58	0.34	5.2	6.49	0.45	6.9
HCOO⁻	−	14	0–0.08	0.04	0.001	2.4	0.037	0.002	4.3
HCOOH:H₂O:CH₃OH	6:68:26	15	0–1.0	0.64	0.03	4.0	0.61	0.05	7.9
CH₃CHO:H₂O	1:20	15	0–2.5	1.65	0.04	2.2	1.66	0.13	7.6
C₂H₅OH:H₂O	1:20	15	0–5.0	1.35	0.10	7.7	1.98	0.14	7.5
CH₃OCH₃:H₂O	1:20	15	0–0.8	0.40	0.05	12.9	0.38	0.07	19.3
CH₃OCHO:CO:H₂CO:CH₃OH	1:20:20:20	15	0–2.0	0.94	0.06	6.0	0.98	0.09	9.2
CH₃COOH:H₂O	1:20	10	0–0.2	0.08	0.02	30.7	−	−	−
CH₃COCH₃:H₂O	1:20	15	0–2.0	0.99	0.03	3.4	1.13	0.08	6.8
CH₃CN:H₂O:CO₂	1:5:2	15	0–1.5	0.70	0.08	10.9	−	−	−
H₂CO	−	10	0.8 ^b	0.8 ^b	−	−	0.8^b	−	−

^† The scaling factors refer to a_i in Eq. 3, which serve as the variables in the least-squares and MCMC fittings. They are proportional to the ice column densities (Eq. 4).

^a The fit range of scaling factors were determined by manually comparing the lab spectra to the observations, as is shown in Figs. 4, 5, and C.1.

^b The scaling factor of the lab spectrum of H₂CO was determined by fitting to an H₂CO band at 6.67 μm, outside of the 6.8–8.8 μm range. The H₂CO band at 8.02 μm was scaled with the same factor of 0.8, which was fixed in both the least-squares and MCMC fittings.

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