where G is the gravitational constant and c s ≡ ≡ k T / μ μ m H is the isothermal sound speed ( γ γ = 1 ) with μ μ as the molecular mass. a is a dimensionless constant which varies based on the density distribution of the cloud. For a uniform mass density a = 1 and for a centrally peaked density a ≈ ≈ 1.67 .