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Table 1
Model parameters.
| Parameter | Unit | Explanation |
|
|
||
| G = 5 × 10-15 | pc3 yr-1  |
gravitation constant |
| κ | yr-1 | epicyclic frequency |
| Q | Toomre parameter | |
| R | pc | galactocentric radius |
| H | pc | thickness of the gas disk |
| H ∗ | pc | thickness of the stellar disk |
| lcl | pc | cloud size |
| vrot | pc yr-1 | rotation velocity |
| Ω = vrot/R | yr-1 | angular velocity |
| ΦV | volume-filling factor | |
| ΦA = ΦVH/lcl | area-filling factor | |
| ρ | M⊙ pc-3 | disk midplane gas density |
| ρCNM | M⊙ pc-3 | cool neutral medium density |
| ρcl = ρ/ ΦV | M⊙ pc-3 | cloud density |
|
M⊙ pc-3 yr-1 | star-formation rate |
| Σ | M⊙ pc-2 | gas surface density |
| Σ∗ | M⊙ pc-2 | stellar surface density |
|
M⊙ pc-2 yr-1 | star-formation rate |
| ξ = 4.6 × 10-8 | pc2 yr-2 | constant relating SN energy input to SF |
|
M⊙ yr-1 | disk mass accretion rate (radial, within the disk) |
| vturb | pc yr-1 | gas turbulent velocity dispersion |
| vrad | pc yr-1 | gas radial velocity |
|
pc yr-1 | stellar vertical velocity dispersion |
| cs | pc yr-1 | sound speed |
| ℳ | Mach number | |
| ν | pc2 yr-1 | viscosity |
| fmol = ΣH2/ (ΣHI + ΣH2) | molecular fraction | |
| α | yr M⊙ pc-3 | constant of molecule formation timescale |
| ldriv | pc | turbulent driving length scale |
| δ = 5 | scaling between the driving length scale and the size of the | |
| largest self-gravitating structures | ||
|
yr-1 | star-formation efficiency |
|
yr | cloud free fall timescale at size l |
|
yr | cloud turbulent timescale at size l (turbulent crossing time) |
|
yr | cloud molecule formation timescale at size l |
| Tg | K | gas temperature |
| Td | K | dust temperature |
Notes. Boldface: free parameters; italic: parameters determined from observations.
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