DOI

https://doi.org/10.48717/ehje-sx70

Project

EW031

Title

e-EVN: EA065K, EW031A, EG123B

Abstract

Dual SMBHs at ~ kpc and sub-kpc scales are progenitors of eventually coalescing binary SMBHs. If both or one of the dual SMBHs are accreting, they may appear as dual or off-nucleus AGNs. Recently a novel and efficient astrometry-based method named varstrometry has been put forward to search for dual SMBHs at high redshift, as the unsynchronized flux variability of off-nucleus and dual AGNs will cause astrometric jitter detectable by Gaia without spatially resolving them. Based on varstrometry we previously selected a rare sample of 5 radio loud quasars with clear Gaia astrometric jitters. With e-MERLIN observations we have revealed a single compact radio source for each of them, and remarkably all exhibit clear Gaia-radio offsets. The detected Gaia-radio offsets suggest these candidate dual SMBHs may have projected separations as small as ~ 0.01 - 0.1'' (~ 0.1 kpc, depending on the optical flux ratio of two SMBHs). Given EVN's better sensitivity and angular resolution, we propose for 5 GHz observations to detect the radio fainter SMBH in each system, which is expected to lie along the Gaia-radio offset line.