Upper limits on the mass and luminosity of Population III-dominated galaxies

TL;DR

This paper models the upper limits of mass and luminosity for Population III-dominated proto-galaxies at redshift ~7, providing constraints based on gas collapse, radiation effects, and observational data.

Contribution

It introduces a novel model predicting upper limits on POPIII galaxy properties, challenging previous candidate identifications like CR7.

Findings

POPIII galaxies at z~7 have specific halo masses and Lyα luminosities.

CR7 likely not a POPIII galaxy based on derived limits.

POPIII galaxies exhibit low HeII emission and high Lyα equivalent widths.

Abstract

We here derive upper limits on the mass and luminosity of Population III (POPIII) dominated proto-galaxies based on the collapse of primordial gas under the effect of angular momentum loss via Ly$\alpha$ radiation drag and the gas accretion onto a galactic centre. Our model predicts that POPIII-dominated galaxies at z ~ 7 are hosted by haloes with $M_{\rm halo} \sim 1.5 \times 10^{8} - 1.1 \times 10^{9} \rm ~M_{\odot}$, that they have Ly$\alpha$ luminosities of $L_{\rm Ly\alpha} \sim 3.0 \times 10^{42} - 2.1 \times 10^{43}$ erg/s, stellar mass of $M_{\rm star} \sim 0.8 \times 10^{5} - 2.5 \times 10^{6} \rm ~M_{\odot}$, and outflowing gas with velocities $V_{\rm out} \sim 40$ km/s due to Ly$\alpha$ radiation pressure. We show that the POPIII galaxy candidate CR7 violates the derived limits on stellar mass and Ly$\alpha$ luminosity and thus is unlikely to be a POPIII galaxy. POPIII-dominated galaxies at z ~ 7 have HeII line emission that is ~1- 3 orders of magnitude lower then that of Ly$\alpha$, they have high Ly$\alpha$ equivalent width of > 300 $\AA$ and should be found close to bright star forming galaxies. The HeII 1640 $\AA$ line is in comfortable reach of next generation telescopes, like the JWST or TMT.