Table 4
Estimations of expansion time for the four H ii regions of Mon R2.
| Analytical calculations and simulations without gravity | Simulations with gravity | Adopted | |||||||
| constant density | decreasing density | constant density | Dec. density | expansion | |||||
| Region | ⟨ ρinitial ⟩ | t Spitzer | ρc | texp (calc) | texp (simu.) | ⟨ ρinitial ⟩ Max | texp (simu) | texp (simu) | time |
| [cm-3] | [kyr] | [cm-3] | [kyr] | [kyr] | [cm-3] | [kyr] | [kyr] | [kyr] | |
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|
|
|||||||||
| central | 2 × 105 | 54 | 2 × 106 | 58 | 53 | 1.7 × 105 | 133 | – | 90 ± 40 |
| western | 2.4 × 104 | 92 | 1 × 106 | 108 | 98 | 1.7 × 104 | 215 | – | 150 ± 50 |
| eastern | 1.5 × 103 | 23 | 4 × 103 | 24 | 23 | 8 × 103 | 170 | 24 | 25 ± 5 |
| northern | 3 × 102 | 310 | 2.5 × 105 | 370 | 355 | 5 × 103 | 3700. | 370 | 350 ± 50 |
Notes. (2) average initial density derived from Eqs. (4) and (10). (3) Expansion time calculated from Eqs. (5) and (6) and using the average density of Col. 2. (4) Constant density of central core derived from Eq. (8) with ρc = 0.005 pc. (5) Expansion time calculated from Eqs. (9) and (6) and using the central density of Col. 4. (6) Expansion time derived from simulations without gravity using a decreasing-density envelope extrapolated up to the central density (Col. 4). Considered as a lower limit (see introduction of Sect. 4.2). (7) Maximum constant density allowing ionisation expansion in simulations with gravity, (see Sect. 4.2.2). (8) Expansion time calculated by simulations using the maximum constant density of Col. 7. Considered as an upper limit. (9) Expansion time derived from simulations with gravity using a decreasing-density envelope extrapolated up to highest possible central density (see Sect. 4.2.3). (10) Adopted expansion time (see Sects. 4.2.4 and 4.3). Errors do not take any systematic effects into account, such as those due to small-scale non-3D geometry or density inhomogeneity.
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