Detection of isolated population III stars with the James Webb Space Telescope

TL;DR

This paper assesses the feasibility of detecting isolated Population III stars with JWST, concluding that such detection is highly unlikely due to their faintness and low surface densities, even with gravitational lensing.

Contribution

It provides a realistic analysis of the detectability of Population III stars with JWST, considering stellar atmospheres, HII regions, and gravitational lensing effects.

Findings

Unlensed Population III stars are beyond JWST's detection capabilities.

Lensed Population III stars are extremely difficult to detect due to low surface densities.

Detecting a Population III star with current models requires a star formation rate ten times higher than predicted.

Abstract

The first population III stars are predicted to form in minihalos at a redshift of approximately 10-30. The James Webb Space Telescope (JWST), tentatively scheduled for launch in 2018, will probably be able to detect some of the first galaxies, but whether it will also be able to detect the first stars remains more doubtful. Here, we explore the prospects of detecting an isolated population III star or a small cluster of population III stars down to redshift 2 in either lensed or unlensed fields. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. We find that unlensed population III stars are beyond the reach of JWST, and that even lensed population III stars will be extremely difficult to detect. However, the main problem with the latter approach is not necessarily that the lensed stars are too faint, but that their surface number densities are too low. To detect even one population III star of 60 solar masses when pointing JWST through the galaxy cluster MACS J0717.5+3745, the lensing cluster with the largest Einstein radius detected so far, the cosmic star formation rate of population III stars would need to be approximately an order of magnitude higher than predicted by the most optimistic current models.