The High Energy X-ray Probe (HEX-P): Probing the Dusty Hearts of Dual AGN

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10 arcsec FWHM) and broad spectral coverage (0.1-150 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR), to enable revolutionary new insights into a variety of important astrophysical problems. A fundamental goal of modern-day astrophysics is to understand the connection between supermassive black hole (SMBH) growth and galaxy evolution. Merging galaxies offer one of the most dramatic channels for galaxy evolution known, capable of driving inflows of gas into galactic nuclei, potentially fueling both star formation and central SMBH activity. Dual AGNs in late-stage mergers are thus ideal candidates to study SMBH growth along the merger sequence by coinciding with the most transformative period for galaxies. However, dual AGNs can be extremely difficult to confirm. Hard X-ray studies offer a relatively contamination-free option for probing the dense obscuring environments predicted to surround the majority of dual AGN in late-stage mergers. But to date only a handful of the brightest and closest systems have been studied above 10 keV due to the demanding instrumental requirements involved. In this poster, we present a HEX-P simulation-based study with the Simulated Observations of X-ray Sources (SOXS) software package to address this issue. We demonstrate the unique capabilities of HEX-P to spatially resolve the soft and - for the first time - hard X-ray counterparts of closely separated dual AGNs in the local Universe. By incorporating state-of-the-art physical torus models with high covering factor obscurers expected in such systems, we realistically reproduce the broadband X-ray spectra expected for such deeply embedded accreting SMBHs. Hard X-ray spatially resolved observations of dual AGNs – accessible only to HEX-P – will hence transform our understanding of dual AGN in the nearby Universe and will complement next-generation optical and infrared observations from upcoming Extremely Large Telescopes over the next two decades. More information on HEX-P, including the full team list, is available at https://hexp.org.