vice.toolkit.J21_sf_law.index1
==============================

Type : float

Default : 1.7

The power-law index of the :math:`\dot{\Sigma}_\star - \Sigma_\text{gas}`
relation at gas surface densities :math:`\Sigma_\text{gas} \leq
\Sigma_{\text{gas},1}`, where :math:`\Sigma_{\text{gas},1}` is the
value of the attribute ``Sigma_g1``.

Example Code
------------
>>> import vice
>>> mw = vice.milkyway(name = "example")
>>> mw.zones[0].tau_star.index1
1.7
>>> for i in range(mw.n_zones):
>>> 	mw.zones[i].tau_star.index1 = 1.5
>>> mw.zones[0].tau_star.index1
1.5