The massive stars that ionised the Universe have short lifetimes and can only be studied near the time of formation , but any low mass stars that formed contemporaneously might be observable in the local Universe today .
We study the abundance pattern and spatial distribution of these ‘ siblings of reionizers ’ ( SoRs ) in the eagle cosmological hydrodynamical simulation .
SoRs tend to be enriched to super-solar levels in \alpha -elements compared to iron .
In eagle galaxies resembling the Milky Way , \sim 40 percent of carbon-enhanced metal poor ( CEMP ) stars are SoRs .
Conversely , \sim 10 percent of all SoRs are CEMP stars .
This fraction increases to \gtrsim 50 percent for SoRs of metallicity [ Fe/H ] < -4 , and at such low metallicities , most of the CEMP stars are of CEMP-no subtype that are lacking neutron capture elements .
Although these numbers may well depend on the details of the physical models implemented in eagle , the trends we describe are robust as they result from the strong feedback from star formation in early galaxies , itself a key ingredient of most current models of galaxy formation .
We further find that most SoRs today reside in halos with mass M _ { h } \gtrapprox 10 ^ { 12 } M _ { \odot } , and 50 percent of them are in the halo of their central galaxy ( distance > 10 kpc ) , mainly because they were accreted onto their current host rather than formed in-situ .
To a good approximation , the SoRs are CEMP-no stars that reside in the stellar halos of massive galaxies , with nearly half of them contributing to the intracluster light in groups and clusters .