vice.toolkit.J21_sf_law.Sigma_g1
================================

Type : float

Default : 5.0e+06

The lower of the two surface densities of gas at which there is a break
in the :math:`\dot{\Sigma}_\star - \Sigma_\text{gas}` relation. Below
this value, the relation scales as a power-law with index set by the
attribute ``index1``. Assumes units of :math:`M_\odot kpc^{-2}`.

.. note:: The value of this attribute should be smaller than that of
	the attribute ``Sigma_g2``, the larger of the two surface
	densities of gas. Default values are chosen based on the aggregate
	data from Bigiel et al. (2010) [1]_ and Leroy et al. (2013) [2]_
	presented in Krumholz et al. (2018) [3]_.

Example Code
------------
>>> import vice
>>> mw = vice.milkyway(name = "example")
>>> mw.zones[0].tau_star.Sigma_g1
5.0e+06
>>> for i in range(mw.n_zones):
>>> 	mw.zones[i].tau_star.Sigma_g1 = 6.0e+06
>>> mw.zones[0].tau_star.Sigma_g1
6.0e+06

.. [1] Bigiel et al. (2010), AJ, 140, 1194
.. [2] Leroy et al. (2013), AJ, 146, 19
.. [3] Krumholz et al. (2018), MNRAS, 477, 2716