Gravitational instability criterion of the filaments (combined skeleton). This criterion is derived from the C¹⁸O-traced linear density estimation and either the thermal pressure (γ, left) or the effective pressure, which also takes into account the C¹⁸O (J = 1−0) velocity dispersion (γ_eff, right). Overlaid are the positions of protostars from Megeath et al. (2016) in white, and class 0 YSOs from HOPS (Furlan et al. 2016) in green.