Open Access
Table 3
Classification of molecular species based on their response to cosmic-ray ionization rates, temperatures, and densities.
| Species group | Abundance behavior | Diagnostic use |
|---|---|---|
| CS, SO, SiO, HCN, HNC, CH3CN | Minimal variations across ζ in all environments | Potentially can act as normalizers for abundance ratios |
| HCO+, H2CO, CH3SH | Systematic changes as function of ζ across all environments; HCO+ increases, others decrease with ζ | Best suited as ζ tracers |
| HCO, HNCO, CH3CHO | Systematic, decreasing trends in protostellar objects as function of ζ | Potentially useful as ζ tracers in protostellar environments |
| NS+, C2S, HC3N, CH2CO, CH3OH, CH3SH⋆, NH2CHO⋆, CH3CCH, CH3CHO⋆, CH3NCO⋆, HCOOCH3⋆, C2H5CN⋆, C2H5OH⋆, CH3OCH3⋆ | Significant abundance changes in protostellar objects at ζ ≳ 10−14 s−1; consistent behavior in shocks | Differentiate shocked vs. protostellar environments at high ζ |
| NS+, CH2CO, CH3OH, CH3SH, NH2CHO HCOOCH3 | ~300 K is a turning point – more pronounced difference between protostellar objects and shocks or behavioral patterns shifts | Selective sensitivity to temperature |
| HCO, HCO+, CH3SH, CH3NCO, HCOOCH3 | Consistent trends across a broad range of temperatures discriminating the gas types | Differentiate shocked vs. protostellar environments based on temperature |
| NS+, CH3SH, CH3CHO, CH3NCO | Abundance always <10−7: NS+ in protostellar objects and post-shocked gas; CH3SH, CH3CHO in protostellar objects; CH3NCO in shocks | Environmental abundance constraints |
Notes. *Species for which the significant abundance changes lead to falling below the detectability threshold (X < 10−14). We discuss this in more detail in Sect. 4.1.1.
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