The eROSITA final equatorial-depth survey (eFEDS): host-galaxy demographics of X-ray AGNs with Subaru Hyper Suprime-Cam

We investigate the physical properties, such as star-forming activity, disc versus bulge nature, galaxy size, and obscuration of 3811 SRG/eROSITA-detected AGNs at 0.2 < z < 0.8 in the eFEDS field. Using Subaru Hyper Suprime-Cam imaging data in the grizy bands, we measure the structural and stellar properties for their host galaxies by performing a 2D AGN-host image decomposition. We find that (1) AGNs can contribute significantly to the total optical light down to log L-X similar to 42 . 5 erg s(-1), thus ignoring the AGN component can significantly bias the structural measurements; (2) AGN hosts are predominately star-forming galaxies at log M * greater than or similar to 11 . 3 M-circle dot; (3) the bulk of AGNs (64 per cent) reside in galaxies with significant stellar discs (S e rsic index n < 2), while their host galaxies become increasingly bulge dominated ( n similar to 4) and quiescent at log M (*) greater than or similar to 11 . 0 M-circle dot (4) the size-stellar mass relation of AGN hosts tends to lie between that of inactive (i.e. non-AGN) star-forming, and quiescent galaxies, suggesting that the physical mechanism responsible for building the central stellar density also efficiently fuel the black hole growth; (5) the hosts of X-ray unobscured AGNs are biased tow ards f ace-on systems, suggesting that some of the obscuration of the nuclei could come from g alaxy-scale g as and dust. This will bias against the detection of unobscured AGNs in gas-rich star forming galaxies, which may partly account for the deficiency of star-forming discs as host galaxies for the most massive AGNs (missing star-forming fraction up to similar to 40 per cent ). Our results are consistent with a scenario in which the black hole and galaxy transform in structure and star-forming activity while grow in mass, as desired to establish the local M-BH - M-bulge relation.