Oral Presentation

Cosmic variance forecasts of high redshift AGNs with Uchuu-nu^2GC

Author(s): Taira Oogi (Ehime University), Tomoaki Ishiyama (Chiba University), Francisco Prada (Instituto de Astrofisica de Andalucia), Darren Croton, Manodeep Sinha (Swinburne University of Technology), Sofia A. Cora (Instituto de Astrofisica de La Plata)

Presenter: Taira Oogi (Ehime University)

Measurements of the luminosity function of active galactic nuclei (AGN) at high redshift (z>~6) are expected to suffer from field-to-field variance, including the cosmic variance and Poisson variance.
Future surveys, such as JWST and Roman, can also be affected by field variance.
We use the Uchuu simulation, a state-of-the-art cosmological N-body simulation with volume 25.7 Gpc^3 and sufficient mass resolution, combined with a semi-analytic galaxy and AGN formation model, the New Numerical Galaxy Catalog (nu^2GC), to investigate the field-to-field variance of the luminosity function of AGNs.
With this Uchuu-nu^2GC model, we quantify the field variance, sigma_{cv}, as a function of survey area, AGN luminosity, and redshift.
The field variance decreases with increasing survey area and decreasing redshift.
We find that at z~6-7, sigma_{cv} hardly depends on the AGN luminosity, in particular for small survey areas (0.01 and 0.1 deg^2).
This is because the typical dark matter halo mass in which AGNs reside does not monotonically increase with increasing luminosity.
Due to the rarity of AGNs, the Poisson variance dominates the total field-to-field variance, in particular, for bright AGNs.
We also examine the effects of parameters related to galaxy formation physics on the field variance.
Finally, we discuss the uncertainties in the estimations of the faint end of AGN luminosity function in recent observations.