Some theories of dense molecular cloud formation involve dynamical environments driven by converging atomic flows or collisions between preexisting molecular clouds .
The determination of the dynamics and physical conditions of the gas in clouds at the early stages of their evolution is essential to establish the dynamical imprints of such collisions , and to infer the processes involved in their formation .
We present multi-transition ^ { 13 } CO and C ^ { 18 } O maps toward the IRDC G035.39-00.33 , believed to be at the earliest stages of evolution .
The ^ { 13 } CO and C ^ { 18 } O gas is distributed in three filaments ( Filaments 1 , 2 and 3 ) , where the most massive cores are preferentially found at the intersecting regions between them .
The filaments have a similar kinematic structure with smooth velocity gradients of \sim 0.4-0.8 km s ^ { -1 } pc ^ { -1 } .
Several scenarios are proposed to explain these gradients , including cloud rotation , gas accretion along the filaments , global gravitational collapse , and unresolved sub-filament structures .
These results are complemented by HCO ^ { + } , HNC , H ^ { 13 } CO ^ { + } and HN ^ { 13 } C single-pointing data to search for gas infall signatures .
The ^ { 13 } CO and C ^ { 18 } O gas motions are supersonic across G035.39-00.33 , with the emission showing broader linewidths toward the edges of the IRDC .
This could be due to energy dissipation at the densest regions in the cloud .
The average H _ { 2 } densities are \sim 5000-7000 cm ^ { -3 } , with Filaments 2 and 3 being denser and more massive than Filament 1 .
The C ^ { 18 } O data unveils three regions with high CO depletion factors ( f _ { D } \sim 5-12 ) , similar to those found in massive starless cores .