vice.toolkit.J21_sf_law.molecular_index
=======================================

Type : float

Default : 0.5

The power-law index on the time-dependence of the molecular gas star
formation efficiency timescale. The normalization will be set such
that the value at :math:`t` = 12 Gyr is equal to the value of the
attribute ``present_day_molecular``.

.. note:: The default value is chosen based on the redshift dependence
	of :math:`\tau_\text{mol}` reported by Tacconi et al. (2018) [1]_
	and a redshift-time relation accurate for :math:`z \lesssim 3`.
	See discussion in section 2 of Johnson et al. (2021) [2]_.

Example Code
------------
>>> import vice
>>> mw = vice.milkyway(name = "example")
>>> mw.zones[0].tau_star.molecular_index
0.5
>>> for i in range(mw.n_zones):
>>> 	mw.zones[i].tau_star.molecular_index = 0.6
>>> mw.zones[0].tau_star.molecular_index
0.6

.. [1] Tacconi et al. (2018), ApJ, 853, 179
.. [2] Johnson et al. (2021), MNRAS, 508, 4484