The Effect of Warm Dark Matter on Early Star Formation Histories of Massive Galaxies: Predictions from the CROC Simulations

Understand

Several massive ($M_{*} > 10^8 M_{\odot}$), high-redshift ($z = 8-10$) galaxies have recently been discovered to contain stars with ages of several hundred million years, pushing the onset of star formation in these galaxies back to $z\sim15$.

• The very existence of stars formed so early may serve as a test for cosmological models with suppressed small-scale power (and, hence, late formation of cosmic structure).
• We explore the ages of the oldest stars in numerical simulations from the Cosmic Reionization On Computers (CROC) project with cold dark matter (CDM) and two warm dark matter (WDM) cosmologies with 3 and 6 keV particles.
• There are statistically significant differences of $\sim 5\;{\rm Myr}$ between average stellar ages of massive galaxies in CDM and 3 keV WDM, while CDM and 6 keV WDM are statistically indistinguishable.