Turbulent scaling (“Larson”) relationship (Larson 1981) between gas velocity dispersion and cloud size in the source plane. Empty red stars show the sizes and line widths of the redshifted and blueshifted components seen in the Ruby within images #1 and #2, respectively. Green and yellow filled circles show similar observations of SDP.81 and the Eyelash from Swinbank et al. (2015) and Swinbank et al. (2011). Empty black circles show giant molecular clouds in the Milky Way. We also show expected line-width size relationships for gas mass surface densities, Σ_gas = 50M_⊙ pc^-2 characteristic for the Milky Way, and for 5000 M_⊙ and 16 000M_⊙ pc^-2, which correspond to the lowest and highest values for the Ruby, respectively (Fig. 6). For each density we show the relationship for virial parameters α_vir = 1 and 5, that is, clouds where turbulent energy either balances gravitational binding energy (solid line), or where it exceeds it by a factor 5 (dashed-dotted lines).