vice.singlezone.tau_star

Type : real number or <function>

Default : 2.0

The star formation rate per unit gas supply in Gyr, defined by

\[\tau_* \equiv M_\text{g}/\dot{M}_*\]

where \(M_\text{g}\) is the ISM gas mass and \(\dot{M}_*\) is the star formation rate. Numbers will be interpreted as a constant value. Functions must accept time in Gyr as the only parameter.

Tip

In infall and gas modes, this parameter can be set to infinity to forcibly shut off star formation.

Note

When the attribute schmidt == True, this is interpreted as the prefactor on gas-dependent star formation efficiency:

\[\tau_*^{-1} = \tau_{*,\text{specified}}^{-1} \left( \frac{M_\text{g}}{M_\text{g,Schmidt}} \right)^{\alpha}\]

where \(\alpha\) is the power-law index on gas-dependent star formation efficiency, set by the attribute schmidt_index, and \(\tau_{*,\text{specified}}\) is the value of this attribute.

Note

Saving functional attributes 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.

Note

In the interstellar medium and star formation literature, this parameter is often referred to as the depletion timescale. In this documentation and in much of the galactic chemical evolution literature, it is usually referred to as the “star formation efficiency timescale.”

Example Code

>>> import vice
>>> sz = vice.singlezone(name = "example")
>>> sz.tau_star = 1
>>> def f(t):
        if 5 <= t <= 6:
                return 1
        else:
                return 2
>>> sz.tau_star = f