The low dust temperatures ( < 14 K ) of Planck Galactic Cold Clumps ( PGCCs ) make them ideal targets to probe the initial conditions and very early phase of star formation .
“ TOP-SCOPE ” is a joint survey program targeting \sim 2000 PGCCs in J=1-0 transitions of CO isotopologues and \sim 1000 PGCCs in 850 \micron continuum emisison .
The objective of the “ TOP-SCOPE ” survey and the joint surveys ( SMT 10-m , KVN 21-m and NRO 45-m ) is to statistically study the initial conditions occurring during star formation and the evolution of molecular clouds , across a wide range of environments .
The observations , data analysis and example science cases for these surveys are introduced with an exemplar source , PGCC G26.53+0.17 ( G26 ) , which is a filamentary infrared dark cloud ( IRDC ) .
The total mass , the length and the mean line-mass ( M/L ) of the G26 filament are \sim 6200 M _ { \sun } , \sim 12 pc and \sim 500 M _ { \sun } Â pc ^ { -1 } , respectively .
Ten massive clumps including eight starless ones are found along the filament .
The most massive Clump as a whole may be still in global collapse while its denser part seems to be undergoing expansion due to outflow feedback .
The fragmentation in G26 filament from cloud scale to clump scale is in agreement with gravitational fragmentation of an isothermal , non-magnetized , and turbulent supported cylinder .
A bimodal behavior in dust emissivity spectral index ( \beta ) distribution is found in G26 , suggesting grain growth along the filament .
The G26 filament may be formed due to large-scale compression flows evidenced by the temperature and velocity gradients across its natal cloud .