Περίληψη :
An ongoing challenge re-invigorated by the James Webb Space Telescope is to understand the formation and evolution of supermassive black holes, which is expected to have occurred primarily during heavily obscured phases. While a complete census of heavily obscured, Compton-thick, black hole growth in the early universe is currently infeasible, local analogues are also notoriously elusive; the latest literature-complete Database of Compton-thick active galactic nuclei (AGN) contains just 66 sources. To tackle such issues, I will present NuLANDS — one of the largest NuSTAR legacy surveys ever performed, dedicated to constructing an obscuration-unbiased census of AGN in the local universe with combined infrared and broadband X-ray constraints. By carefully characterising the average circum-nuclear obscuration properties of NuLANDS AGN, I will show the sample is fully consistent with predictions from the Cosmic X-ray Background, for the first time devoid of any bias corrections. NuLANDS crucially shows we are currently missing of order 200 Compton-thick AGN within 200 Mpc, proving we have barely scratched the surface of an obscured black hole growth census. A striking example is our discovery of the first Compton-thick AGN predicted to be rapidly accreting with an extremely soft intrinsic X-ray continuum. While such rapidly accreting, Compton-thick AGN are expected to be prevalent in the early universe, this source represents the first local analogue of that critical growth phase. Existing at a mere 24 Mpc and missed by all previous surveys, the source highlights the vast discovery space that remains to be explored even in our own cosmic backyard.
