Near-infrared emission line diagnostics for AGN from the local Universe to z ∼ 3

Optical rest-frame spectroscopic diagnostics are usually employed to distinguish between star formation and active galactic nucleus (AGN) powered emission. However, this method is biased against dusty sources, hampering a complete census of the AGN population across cosmic epochs. To mitigate this e...

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Veröffentlicht in:Astronomy and astrophysics (Berlin) 2023-11, Vol.679, p.A80
Hauptverfasser: Calabrò, Antonello, Pentericci, Laura, Feltre, Anna, Haro, Pablo Arrabal, Radovich, Mario, Seillé, Lise-Marie, Oliva, Ernesto, Daddi, Emanuele, Amorín, Ricardo, Bagley, Micaela B., Bisigello, Laura, Buat, Véronique, Castellano, Marco, Cleri, Nikko J., Dickinson, Mark, Fernández, Vital, Finkelstein, Steven L., Giavalisco, Mauro, Grazian, Andrea, Hathi, Nimish P., Hirschmann, Michaela, Juneau, Stéphanie, Kartaltepe, Jeyhan S., Koekemoer, Anton M., Lucas, Ray A., Papovich, Casey, Pérez-González, Pablo G., Pirzkal, Nor, Santini, Paola, Trump, Jonathan, de la Vega, Alexander, Wilkins, Stephen M., Yung, L. Y. Aaron, Cassata, Paolo, Gobat, Raphael A. S., Mascia, Sara, Napolitano, Lorenzo, Vulcani, Benedetta
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Sprache:eng
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Zusammenfassung:Optical rest-frame spectroscopic diagnostics are usually employed to distinguish between star formation and active galactic nucleus (AGN) powered emission. However, this method is biased against dusty sources, hampering a complete census of the AGN population across cosmic epochs. To mitigate this effect, it is crucial to observe at longer wavelengths in the rest-frame near-infrared (near-IR), which is less affected by dust attenuation and can thus provide a better description of the intrinsic properties of galaxies. AGN diagnostics in this regime have not been fully exploited so far, due to the scarcity of near-IR observations of both AGN and star-forming galaxies, especially at redshifts higher than 0.5. Using Cloudy photoionization models, we identified new AGN – star formation diagnostics based on the ratio of bright near-IR emission lines, namely [SIII] 9530 Å, [CI] 9850 Å, [PII] 1.188 μm, [FeII] 1.257 μm, and [FeII] 1.64 μm to Paschen lines (either Pa γ or Pa β ), providing simple, analytical classification criteria. We applied these diagnostics to a sample of 64 star-forming galaxies and AGN at 0 ≤  z  ≤ 1, and 65 sources at 1 ≤  z  ≤ 3 recently observed with JWST-NIRSpec in CEERS. We find that the classification inferred from the near-IR is broadly consistent with the optical one based on the BPT and the [SII]/H α ratio. However, in the near-IR, we find ∼60% more AGN than in the optical (13 instead of eight), with five sources classified as “hidden” AGN, showing a larger AGN contribution at longer wavelengths, possibly due to the presence of optically thick dust. The diagnostics we present provide a promising tool to find and characterize AGN from z  = 0 to z  ≃ 3 with low- and medium-resolution near-IR spectrographs in future surveys.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361/202347190