vice.singlezone.eta

Type : real number or <function>

Default : 2.5

The mass loading factor, defined as the ratio of the mass outflow rate to the star formation rate.

\[\eta \equiv \frac{\dot{M}_\text{out}}{\dot{M}_\star}\]

Note

If the attribute smoothing is nonzero, this relationship generalizes to

\[\dot{M}_\text{out} = \eta(t) \langle\dot{M}_\star\rangle_{\tau_\text{s}} = \Bigg \lbrace { \frac{\eta(t)}{t}\int_0^t \dot{M}_\star(t') dt' (t < \tau_\text{s}) \atop \frac{\eta(t)}{\tau_\text{s}}\int_{t - \tau_\text{s}}^t \dot{M}_\star(t') dt'\ (t \geq \tau_\text{s}) }\]

where \(\tau_\text{s}\) is the value of the attribute, the outflow smoothing time.

Note also that the time-average is over the star formation rate only, and not the mass-loading factor.

Note

Saving this functional attribute with VICE outputs requires the package dill, an extension to pickle in the Python standard library. It is recommended that VICE user’s install dill >= 0.2.0.

Example Code

>>> import vice
>>> sz = vice.singlezone(name = "example")
>>> sz.eta = 2
>>> def f(t):
        if t <= 2:
                return 5
        else:
                return 1
>>> sz.eta = f