Signatures of Exploding Supermassive PopIII Stars at High Redshift in JWST, EUCLID and Roman Space Telescope

TL;DR

This paper models the observable signatures of supermassive PopIII star explosions at high redshift, predicting their brightness, duration, and detectability with JWST, EUCLID, and Roman Space Telescope, to inform future observations of early universe black hole formation.

Contribution

It introduces a semi-analytic model for supermassive PopIII star explosions, predicting their light curves, spectra, and detectability, advancing understanding of early supermassive black hole formation channels.

Findings

SMS explosions reach luminosities of 10^{45-47} erg/s.

They last 10-200 years in source frame, up to 3000 years with cosmic dilation.

JWST can detect these explosions up to z=20, EUCLID and RST up to z~12.

Abstract

Recently discovered supermassive black holes with masses of $\sim10^8\,M_\odot$ at redshifts $z\sim9$-$11$ in active galactic nuclei (AGN) pose severe challenges to our understanding of supermassive black hole formation. One proposed channel are rapidly accreting supermassive PopIII stars (SMSs) that form in large primordial gas halos and grow up to $<10^6\,M_\odot$. They eventually collapse due to the general relativistic instability and could lead to supernova-like explosions. This releases massive and energetic ejecta that then interact with the halo medium via an optically thick shock. We develop a semi-analytic model to compute the shock properties, bolometric luminosity, emission spectrum and photometry over time. The initial data is informed by stellar evolution and general relativistic SMS collapse simulations. We find that SMS explosion light curves reach a brightness $\sim10^{45\mathrm{-}47}\,\mathrm{erg/s}$ and last $10$-$200$ years in the source frame - up to $250$-$3000$ years with cosmic time dilation. This makes them quasi-persistent sources which vary indistinguishably to little red dots and AGN within $0.5$-$9\,(1+z)$ yrs. Bright SMS explosions are observable in long-wavelength JWST filters up to $z\leq20$ ($24$-$26$ mag) and pulsating SMSs up to $z\leq15$. EUCLID and the Roman space telescope (RST) can detect SMS explosions at $z<11$-$12$. Their deep fields could constrain the SMS rate down to $10^{-11}$Mpc$^{-3}$yr$^{-1}$, which is much deeper than JWST bounds. Based on cosmological simulations and observed star formation rates, we expect to image up to several hundred SMS explosions with EUCLID and dozens with RST deep fields.