vice.toolkit.J21_sf_law.molecular

Calculate the star formation efficiency timescale of molecular gas at a given simulation time.

Signature: x.molecular(time)

Parameters

xJ21_sf_law

An instance of this class.

timefloat

The simulation time in Gyr.

Returns

tau_star_molfloat

The star formation efficiency timescale \(\tau_\star\) for molecular gas only (\(\tau_\text{mol}\)), defined accordingly:

\[\tau_\text{mol} = \tau_{\text{mol},0} \left(\frac{0.5 + t}{t_0}\right)^\gamma\]

where \(\tau_{\text{mol},0}\) is the value of \(\tau_\text{mol}\) at the present day, \(t_0\) is the present-day age of the universe (assumed to be 13.7 Gyr), \(\gamma\) is the power-law index, and \(t\) is the parameter time passed to this function. A value of 0.5 is added, beacuse the onset of star formation is assumed to occur 0.5 Gyr following the big bang in the Johnson et al. (2021) models [1].

The values of \(\tau_{\text{mol},0}\) and \(\gamma\) are controlled by the attributes present_day_molecular and molecular_index, respectively.

Example Code

>>> import vice
>>> mw = vice.milkyway(name = "example")
>>> mw.zones[0].tau_star.molecular(0)
0.6617825960083583
>>> mw.zones[0].tau_star.molecular(5)
1.3776103291490314
>>> mw.zones[0].tau_star.molecular(13.2)
2.0