Cold Filamentary Accretion and the Formation of Metal Poor Globular
  Clusters and Halo Stars
  We propose that cold filamentary accretion in massive galaxies at high
redshift can lead to the formation of star-forming clumps in the halos of these
galaxies without the presence of dark matter sub-structure. In certain cases,
these clumps can be the birth places of metal poor globular-clusters (MP GCs).
Using cosmological simulations, we show that narrow streams of dense gas
feeding massive galaxies from the cosmic web can fragment, producing
star-forming clumps. We then derive an analytical model for the properties of
streams as a function of halo mass and redshift, and assess when these are
gravitationally unstable, when this can lead to collapse and star-formation in
the halo, and when it may result in the formation of MP GCs. For stream
metalicities >~1% solar, this is likely to occur at z>4.5. At z~6, the
collapsing clouds have masses of (5-10)x10^7 M_{sun} and the average stream
pressure is ~10^6 K cm^{-3}. The conditions for GC formation are met in the
extremely turbulent "eyewall" at ~0.3 R_{vir}, where counter-rotating streams
can collide, driving very large densities. Our scenario can account 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 and the
host halo. For MW mass halos, we infer that ~30% of MP GCs could have formed in
this way, the remainder likely accreted in mergers. Our predictions for GC
formation along circumgalactic filaments at high-redshift are testable with
JWST.
