Star formation within the Central Molecular Zone ( CMZ ) may be intimately linked to the orbital dynamics of the gas .
Recent models suggest that star formation within the dust ridge molecular clouds ( from G0.253+0.016 to Sgr B2 ) follows an evolutionary time sequence , triggered by tidal compression during their preceding pericentre passage .
Given that these clouds are the most likely precursors to a generation of massive stars and extreme star clusters , this scenario would have profound implications for constraining the time-evolution of star formation .
In this Letter , we search for the initial conditions of the protocluster clouds , focusing on the kinematics of gas situated upstream from pericentre .
We observe a highly-regular corrugated velocity field in \ { l, v _ { LSR } \ } space , with amplitude and wavelength A = 3.7 \pm 0.1 km s ^ { -1 } and \lambda _ { vel,i } = 22.5 \pm 0.1 pc , respectively .
The extremes in velocity correlate with a series of massive ( \sim 10 ^ { 4 } M _ { \odot } ) and compact ( R _ { eq } \sim 2 pc ) , quasi-regularly spaced ( \sim 8 pc ) , molecular clouds .
The corrugation wavelength and cloud separation closely agree with the predicted Toomre ( \sim 17 pc ) and Jeans ( \sim 6 pc ) lengths , respectively .
We conclude that gravitational instabilities are driving the condensation of molecular clouds within the Galactic Centre gas stream .
Furthermore , we speculate these seeds are the historical analogue of the dust-ridge molecular clouds , representing the initial conditions of star and cluster formation in the CMZ .