The Jeans Mass at First Collapse with Bounce-Set Initial Conditions: Timing the First Stars

The first stars formed in halos just massive enough for their gas to cool, of order a million solar masses, at redshifts around twenty to thirty. For a cutoff at 10 per megaparsec the first collapse moves to redshift 15.5, a delay of 4.5 units of redshift from the standard expectation near twenty; for a cutoff at 50 per megaparsec the timing is essentially standard, at redshift 18.1. The signature is therefore confined to the same cutoff range that other probes bound, and it offers a consistency check rather than a competing constraint: if the cutoff were large enough to delay the first stars noticeably, the variance and dwarf-galaxy bounds would already have objected. Computed from stated assumptions, not measured.