On the observability and identification of Population III galaxies with JWST

Understand

We utilise theoretical models of Population III stellar+nebular spectra to investigate the prospects of observing and accurately identifying Population III galaxies with JWST using both deep imaging and spectroscopy.

• We investigate a series of different colour cuts, finding that a combination of NIRCam and MIRI photometry through the F444W-F560W, F560W-F770W colours offers the most robust identifier of potential $z=8$ Pop III candidates.
• We calculate that NIRCam will have to reach $\sim$28.5-30.0 AB mag depths (1-20 h), and MIRI F560W must reach $\sim$27.5-29.0 AB mag depths (10-100 h) to achieve $5\sigma$ continuum detections of $M_* = 10^6~\mathrm{M}_\odot$ Pop III galaxies at $z=8$.
• We also discuss the prospects of identifying Pop III candidates through slitless and NIRSpec spectroscopic surveys that target Ly$\alpha$, H$\beta$ and/or He II $\lambda 1640$.