The Stellar Initial Mass Function at the Epoch of Reionization

Understand

I provide estimates of the ultraviolet and visible light luminosity density at z~6 after accounting for the contribution from faint galaxies below the detection limit of deep Hubble and Spitzer surveys.

• I find the rest-frame V-band luminosity density is a factor of ~2-3 below the ultraviolet luminosity density at z~6.
• This implies that the maximal age of the stellar population at z~6, for a Salpeter initial mass function, and a single, passively evolving burst, must be <100 Myr.
• If the stars in z~6 galaxies are remnants of the star-formation that was responsible for ionizing the intergalactic medium, reionization must have been a brief process that was completed at z<7.