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Table 2

Observed ice compositions in various massive young stellar objects (MYSOs), low-mass young stellar objects (LYSOs), and background (BG) stars, along with a Kuiper Belt comet, compared with model predictions at the best-fitting times derived from gas-phase abundances.

Ice species XH2O(%) Literature (% H2O)
M1 M2 M3 M4 BG Stars MYSOs LYSOs Comets
H2O* 9.28(−5) 6.95(−5) 1.16(−4) 5.71(−5) 100 100 100 100
CO 91.84 134.92 18.68 87.17 9-67 (a) 3-26 (a) <3-85(a) 0.4-30 (a,e)
CO2 2.84 0.76 16.96 37.63 14-43 (a) 11-27 (a) 12-50 (a) 4-30 (a,e)
CH4 12.70 6.36 32.53 7.12 <3(a) 1-3 (a) 1-11 (a) 0.4-1.6 (a,e)
NH3 0.86 3.37 1.38 3.35 <7 (a) ~7 (a) 3-10 (a) 0.2-1.4 (a,e)
CH3OH 2.93 0.45 3.98 1.59 <1-12 (a) <3-31 (a) <1-25 (a) 0.2-7 (a,e)
H2CO 15.88 5.31 7.04 8.64 ~2-7 (a) −6 (a) 0.11-1.0 (a,e)
HCOOH 5(-3) 3(-3) 4.24 13.69 <2 (a) <0.5-6 (a) <0.5-4 (a) 0.06-0.14 (a,e)
CH3CHO 1(-3) 5(-5) 0.02 1.03 <2.3 (b) 0.047(f,g)
C2H5OH 4(-4) 2(-4) 0.31 0.13 <1.9 (b) 0.039(f,g)
HCOOCH3 0.06 0.02 2.98 2.14 <2.3 (c) 0.0034 (f,g)
CH3NH2 0.01 1(-3) 0.08 0.19 <3.4 (b) <16 (d)
SO2 3(-5) 6(-10) 6(-4) 5(-3) <0.9-1.4 (a) 0.08-0.76 (a) 0.2 (a,e)

Notes. Model columns (M1-M4) represent specific simulation setups, where a(b) = a × 10b, and the observation columns summarize results from various astronomical sources. A dash (-) indicates no data. The best-fitting times for models M1-M4 were 4, 9.64, 4, and 9.64 Myr, respectively. (*)For H2O, we report the total water abundance relative to gas-phase H for each model. References: (a)Boogert et al. (2015), (b)Terwisscha van Scheltinga et al. (2018), (c)Terwisscha van Scheltinga et al. (2021), (d) Rachid et al. (2020), (e)Mumma & Charnley (2011), (f)Rocha et al. (2024), (g)Rubin et al. (2019).

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