Uchuu$\nu^2$GC galaxies and AGN: Cosmic variance forecasts of highredshift AGN for JWST, Euclid, and LSST
Abstract
Measurements of the luminosity function of active galactic nuclei (AGN) at high redshift ($z\gtrsim 6$) are expected to suffer from fieldtofield variance, including cosmic and Poisson variances. Future surveys, such as those from the Euclid telescope and James Webb Space Telescope (JWST), will also be affected by field variance. We use the Uchuu simulation, a stateoftheart cosmological $N$body simulation with 2.1 trillion particles in a volume of $25.7~\mathrm{Gpc}^3$, that has sufficient mass resolution to resolve dwarfsize systems, combined with a semianalytic galaxy and AGN formation model, to generate the Uchuu$\nu^2$GC catalog, publicly available, that allows us to investigate the fieldtofield variance of the luminosity function of AGN. With this Uchuu$\nu^2$GC model, we quantify the cosmic variance as a function of survey area, AGN luminosity, and redshift. In general, cosmic variance decreases with increasing survey area and decreasing redshift. We find that at $z\sim67$, the cosmic variance depends weakly on AGN luminosity, in particular for small survey areas (0.01 and 0.1 deg$^2$). This is because the typical mass of dark matter haloes in which AGN reside does not significantly depend on luminosity. Due to the rarity of AGN, Poisson variance dominates the total fieldtofield variance, especially for bright AGN. We discuss uncertainties present in the estimation of the faintend of the AGN luminosity function from recent observations, and extend this to make predictions for the expected number of AGN and their variance for upcoming observations with Euclid, JWST, and the Legacy Survey of Space and Time (LSST). In particular, we predict that the Euclid deep survey will find 120240 (1680) AGN  depending on the model  with restframe UV absolute magnitude brighter than $20$ ($20.5$) at $z=6.3$ ($z=7$) in the Euclid Hband deep survey (abridged).
 Publication:

arXiv eprints
 Pub Date:
 July 2022
 arXiv:
 arXiv:2207.14689
 Bibcode:
 2022arXiv220714689O
 Keywords:

 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 17 pages, 17 figures, submitted to MNRAS, All Uchuu$\nu^2$GC data used for this paper is publicly available in our Skies &