Kashlinsky et al .
( 2005 ) find a significant cosmic infrared background fluctuation excess on angular scales \mathrel { \hbox to 0.0 pt { \lower 3.0 pt \hbox { $ \sim$ } } \raise 2.0 pt \hbox { $ > $ } } 50 arcsec that can not be explained by instrumental noise or local foregrounds .
The excess has been tentatively attributed to emission from primordial very massive ( PopIII ) stars formed \leq 200 Myr after the Big Bang .
Using an evolutionary model motivated by independent observations and including various feedback processes , we find that PopIII stars can contribute < 40 % of the total background intensity ( \nu J _ { \nu } \sim 1 - 2 nW m ^ { -2 } sr ^ { -1 } in the 0.8-8 \mu m range ) produced by all galaxies ( hosting both PopIII and PopII stars ) at z \geq 5 .
The infrared fluctuation excess is instead very precisely accounted by the clustering signal of galaxies at z \geq 5 , predominantly hosting PopII stars with masses and properties similar to the present ones .