Probing Population III Initial Mass Functions with He ii/Hα Intensity Mapping

Abstract We demonstrate the potential of line-intensity mapping to place constraints on initial mass function (IMF) Population III stars via measurements mean He ii 1640 Å/H α ratio. extend 21cmFAST code with modern high-redshift galaxy-formation and photoionization models, estimate line emission from II galaxies at redshifts 5 ≤ z 20. In our ratio values /H ≳ 0.1 indicate top-heavy IMFs several hundred solar masses, reached 10 when dominate star formation. A next-generation space mission capabilities moderately superior those CDIM will be able probe this scenario by measuring H fluctuation power spectrum signals their cross-correlation high significance up ∼ Moreover, regardless IMF, a value ≲ 0.01 indicates low formation and, therefore, it end period dominated stellar population. However, detection corresponding may only possible for or through stronger signal. Finally, are complex interpret because they can driven competing effects. discuss how various different combination other probes assist in constraining IMF case.