A candidate high-redshift tidal disruption event at z ≳ 7 in COSMOS-Web: the first photometric search with JWST

In this work, we predict TDE rates across upcoming deep surveys with Rubin, Roman, and JWST, first assuming the properties and rates of TDEs at low redshifts determined from the optically-selected sample from the Zwicky Transient Facility (ZTF). Extrapolating the local rate to higher redshifts, we expect thousands of TDEs per year in Rubin, with hundreds at z > 1, tens per year in the Roman High Latitude Time Domain Survey (up to z ∼ 6), and thousands in the Roman Wide Area Survey (up to z ∼ 7), but fewer than one TDE in COSMOS-Web. We suggest, however, that TDE rates at z > 5 may be enhanced by up to two orders of magnitude compared to the local rate because of the higher central stellar mass densities, top-heavy initial mass function, and larger post-merger fractions of galaxies in the early Universe, as revealed by JWST. To test this, we develop a novel methodology for identifying high-redshift TDEs in deep surveys through color and morphology selection criteria and apply it to COSMOS-Web. We discover a high redshift TDE candidate, at redshift 7.2 ⪅ z ⪅ 8.0 which, if validated, confirms the enhancement of the high-redshift TDE rate of at least an order of magnitude. This work is the first demonstration of a method of identifying TDE candidates without time-domain information, and can be applied to find the dozens of z > 4 TDEs present in the Roman Wide Area Survey.