Open Access
Table 1.
Definitions of timescales considered in this work.
| Symbol | Description |
|---|---|
| tff(ρ0) | The cloud free-fall time, or the free-fall time for an object with mean density ρ0 |
| tff(ρ) | The free-fall time at density ρ |
| tcoll(ρ) | The time for gas at density ρ to collapse and form cores, often written as tcoll = tff, where ϕt is a scaling factor of order unity. |
| trenew | The length of time that a cloud’s density PDF is renewed relative to the moment its density PDF was set at t = 0, or the duration of PDF renewal |
| tstart | The moment core formation begins in the cloud relative to t = 0 |
| tsf | The visibility timescale of any given star formation tracer |
| tlife | The cloud lifetime |
| tobs | The time when a cloud is observed relative to t = 0. For clouds observed with long visibility (extragalactic) star formation tracers, tobs ≈ tlife |
| tstop | The time when a cloud’s PDF renewal stops relative to t = 0. For long-timescale star formation tracers, tobs > tstop. |
| tno cl | The time between cloud formation events |
| tno sf | The time clouds spend in an inert phase, between star formation events |
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.