Conditions for detecting lensed Population III galaxies in blind surveys with the James Webb Space Telescope, the Roman Space Telescope and Euclid

Abstract

Dark matter halos that reach the HI-cooling mass without prior star formation or external metal pollution represent potential sites for the formation of small Population III galaxies at high redshifts. Such objects are expected to attain total stellar masses of at most 10 6 solar masses and will therefore typically be extremely faint. Gravitational lensing may in rare cases boost their fluxes to detectable levels, but to find even a small number of such objects requires very large sky areas to be surveyed. Because of this, a small, wide-field telescope can in principle offer better detection prospects than a large telescope with a smaller field of view. Here, we derive the Pop III galaxy properties -in terms of comoving number density, stellar initial mass function and total stellar mass -required to allow gravitational lensing to lift such objects at redshift 𝑧 = 5 − 16 above the detection thresholds of blind surveys carried out with the James Webb space telescope (JWST), the Roman space telescope (RST) or Euclid. We find that the prospects for photometric detections of Pop III galaxies are promising, and that they are better for RST than for JWST and Euclid. However, the Pop III galaxies favoured by current simulations have number densities too low to allow spectroscopic detections based on the strength of the HeII1640 emission line in any of the considered surveys unless very high star formation efficiencies (𝜖 0.1) are envoked.

On the single-event-based identification of primordial black hole mergers at cosmological distances

“…Claims based on individual events would thus benefit from better knowledge of the properties of Pop III stars and their remnants, notably the highest rate at which they merge. Forthcoming facilities such as the JWST, the Roman space telescope or Euclid are expected to probe the properties of Pop III stars by accessing Pop III galaxies in blind surveys [84]. More information will be yielded by instrument such as SPHEREx, by precisely measuring the near infrared background [85]; and mission concepts like THESEUS, by detecting the most distant long gamma-ray burst [86].…”

Detecting gravitational lenses using machine learning: exploring interpretability and sensitivity to rare lensing configurations

“…Furthermore, extreme ultrahigh-redshift lensed galaxies will be preferentially detected only at near-infrared wavelengths, and though very rare on the sky (e.g. Marchetti et al 2017;Vikaeus et al 2021), will be high priority targets for follow-ups. Our results show that it is not yet clear whether such red background lensed sources will be systematically selected against with default lens finders.…”

Some First Stars Were Red: Detecting Signatures of Massive Population III Formation Through Long-Term Stochastic Color Variations

“…• If Halo A-like objects only form at z 10, then robustly detecting them without the benefit of lensing would be too time-intensive for blind surveys (e.g., reaching S/N∼10 for z∼12 objects would require ∼68 hours on JWST). Shallow or pure parallel surveys with JWST, however, should soon reveal overdensities at z∼10, as will deep surveys with e.g., the Roman Space Telescope (Vikaeus et al 2021). These overdensities may then be targeted for deep follow-up observations.…”