We propose that filamentary accretion , the main mode of accretion in massive galaxies at high redshift , can lead to the formation of massive star-forming clumps in the halos of these galaxies that are not associated with dark matter sub-structure .
In certain cases , these clumps can be the birth places of metal poor globular-clusters ( MP GCs ) .
Halos that constitute greater than 2 - \sigma fluctuations in the cosmic density field are fed by narrow , dense streams of cold gas that flow along the cosmic web filaments .
At z = 6 ( z = 3 ) , this corresponds to halos more massive than \sim 10 ^ { 9 } \ > ( 10 ^ { 11.5 } ) \ > M _ { \odot } , which evolve into halos with virial masses M _ { v } \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 10 ^ { 10 } \ > ( 10 ^ { 12 } ) \ > M _ % { \odot } at z = 0 .
Using cosmological simulations , we show that these streams can fragment and produce star-forming bound clumps .
We then derive an analytical model to characterize the properties of streams as a function of halo mass and redshift and assess when these will be gravitationally unstable , when this can lead to star-formation in the halo , and when it may result in the formation of MP GCs .
We show that the streams are likely to undergo gravitational instability on a timescale shorter than the halo crossing time .
At z \sim 6 , the collapsing clouds have masses of M _ { J } \sim 5 - 10 \times 10 ^ { 7 } M _ { \odot } while the average pressure in the streams is P \sim 10 ^ { 6 } { cm } ^ { -3 } { K } , consistent with the requirements to produce GCs with typical z = 0 masses of \sim 2 \times 10 ^ { 5 } M _ { \odot } .
At z \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 4.5 the cooling time in the clouds is shorter than the halo crossing time for stream metalicities of Z \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 0.01 Z _ { \odot } , as seen in simulations .
We suggest that the conditions for the formation of MP GCs are met in the inner \sim 0.3 R _ { v } , the extremely turbulent ‘ ‘ eyewall ’ ’ where counter-rotating streams can collide , dissipating angular momentum and driving very large densities .
Our scenario naturally accounts for the observed kinematics and spatial distribution of MP GCs , the correlation between their mass and metalicity , and the mass ratio between the GC system ( GCS ) and the host halo .
For a MW mass halo we infer that \sim 30 \% of its MP GCs could have formed in this way , with the fraction increasing with decreasing halo mass .
The remainder of the MP GCs were likely accreted in mergers .
Our predictions for star and cluster-formation along filamentary structures around galaxies at high-redshift can be tested with upcoming observations with JWST .