The role of SPICA-like missions and the Origins Space Telescope in the quest for heavily obscured AGN and synergies with Athena
L. Barchiesi, F. Pozzi, C. Vignali, F. J. Carrera, F. Vito, F. Calura, L. Bisigello, G. Lanzuisi, C. Gruppioni, E. Lusso, I. Delvecchio, M. Negrello, A. Cooray, A. Feltre, J. A. Fernández-Ontiveros, S. Gallerani, H. Kaneda, S. Oyabu, M. Pereira-Santaella, E. Piconcelli, C. Ricci, G. Rodighiero, L. Spinoglio, F. Tombesi
In the BH-galaxy co-evolution framework, most of the star-formation (SF) and the black hole (BH) accretion is expected to take place in highly obscured conditions. Thus, obscured AGN are difficult to identify in optical or X-ray bands, but shine bright in the IR. Moreover, X-ray background (XRB) synthesis models predict that a large fraction of the yet-unresolved XRB is due to the most obscured (Compton thick, CT) of these AGN. In this work, we investigate the synergies between putative IR missions (using SPICA, proposed for ESA/M5 but withdrawn in October 2020, and Origins Space Telescope, OST, as `templates') and the X-ray mission Athena, which should fly in early 2030s, in detecting and characterizing AGN, with a particular focus on the most obscured ones. Using an XRB synthesis model, we estimated the number of AGN and the number of those which will be detected in the X-rays. For each AGN we associated an optical-to-FIR SED from observed AGN with both X-ray data and SED decomposition, and used these SEDs to check if the AGN will be detected by SPICA-like or OST at IR wavelengths. We expect that, with the deepest Athena and SPICA-like (or OST) surveys, we will be able to detect in the IR more than 90% of all the AGN (down to L2−10keV∼1042erg/s and up to z∼10) predicted by XRB synthesis modeling, and we will detect at least half of them in the X-rays. Athena will be extremely powerful in detecting and discerning moderate- and high-luminosity AGN. We find that the most obscured and elusive CT-AGN will be exquisitely sampled by SPICA-like mission or OST and that Athena will allow a fine characterization of the most-luminous ones. This will provide a significant step forward in the process of placing stronger constraints on the yet-unresolved XRB and investigating the BH accretion rate evolution up to very high redshift (z≥4).
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