258 | | [[latex($t_{cross}=\frac{L}{C_s}$)]] |
259 | | |
260 | | where the sound speed for 10 K molecular gas is ~.2 km/s and L is .05 pc. This gives: |
261 | | |
262 | | [[latex($\boxed{t_{cross}=7.714e+12 ~s}$)]] |
263 | | |
264 | | or 244 KY. |
265 | | |
266 | | How long it takes the gas to respond to changes in the internal energy depends on the crossing time over some appropriate length scale. |
| 258 | [[latex($t_{cross}=\frac{r}{C_s}$)]] |
| 259 | |
| 260 | where the sound speed for 10 K molecular gas is ~.2 km/s and r=.0069 pc. This gives: |
| 261 | |
| 262 | [[latex($\boxed{t_{cross}=~33~ kyr}$)]] |
| 263 | |
| 264 | |
| 265 | How long it takes the gas density to changes in response to changes in thermal energy corresponds to the crossing time, for some appropriate length scale. |