Abstract :
[en] We analyze Spitzer spectra of 140 active galactic nuclei (AGN) detected in the hard X-rays (14-195 keV) by the Burst Alert Telescope on board Swift. This sample allows us to probe several orders of magnitude in black hole masses (106-109 M ⊙), Eddington ratios (10−3-1), X-ray luminosities (1042-1045 erg s−1), and X-ray column densities (1020-1024 cm−2). The AGN emission is expected to be the dominant source of ionizing photons with energies ≳50 eV, and therefore, high-ionization mid-infrared (MIR) emission lines such as [Ne v] 14.32, 24.32 μm and [O iv] 25.89 μm are predicted to be good proxies of AGN activity, and robust against obscuration effects. We find high detection rates (≳85%-90%) for the MIR coronal emission lines in our AGN sample. The luminosities of these lines are correlated with the 14-150 keV luminosity (with a typical scatter of σ ∼0.4-0.5 dex), strongly indicating that the MIR coronal line (CL) emission is driven by AGN activity. CLs are also tightly correlated to the bolometric luminosity (σ ∼0.2-0.3 dex), calculated from careful analysis of the spectral energy distribution. We find that the relationship between the CL strengths and L 14-150 keV is independent of black hole mass, AGN luminosity, and Eddington ratio, and mostly not affected by high X-ray column densities. This confirms that the MIR CLs can be used as unbiased tracers of the AGN power for X-ray luminosities in the 1042-1045 erg s−1 range.
Funding text :
We thank the referee for the suggestions and very detailed comments, which helped us improve the manuscript. We thank Teng Liu for his useful comments on our work. C.R. acknowledges support from Fondecyt Regular grant 1230345, ANID BASAL project FB210003, and the China-Chile joint research fund. M.J.T. acknowledges support from a FONDECYT postdoctoral fellowship (3220516). Y.D. acknowledges support from a FONDECYT postdoctoral fellowship (3230310). J.M.C.'s contribution was supported by an appointment to the NASA Postdoctoral Program at the NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. R.R. acknowledges support from the Fundaci\u00F3n Jes\u00FAs Serra and the Instituto de Astrof\u00EDsica de Canarias under the Visiting Researcher Programme 2023-2025 agreed between both institutions. R.R. also acknowledges support from the ACIISI, Consejer\u00EDa de Econom\u00EDa, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2021010079, and the support through the RAVET project by the grant PID2019-107427GB-C32 from the Spanish Ministry of Science, Innovation and Universities MCIU. This work has also been supported through the IAC project TRACES, which is partially supported by the state budget and the regional budget of the Consejer\u00EDa de Econom\u00EDa, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community. RR also thanks to Conselho Nacional de Desenvolvimento Cient\u00EDfico e Tecnol\u00F3gico (CNPq, Proj. 311223/2020-6, 304927/2017-1 and 400352/2016-8), Funda\u00E7\u00E3o de amparo \u00E0 pesquisa do Rio Grande do Sul (FAPERGS, Proj. 16/2551-0000251-7 and 19/1750-2), Coordena\u00E7\u00E3o de Aperfei\u00E7oamento de Pessoal de N\u00EDvel Superior (CAPES, Proj. 0001). This work was funded by ANID through CATA-BASAL FB210003 (FEB); FONDECYT Regular 1200495 (FEB) and 1241005 (FEB); and Millennium Science Initiative AIM23-0001 and ICN12_009 (FEB). K.K.G. thanks the Belgian Federal Science Policy Office (BEL- SPO) for the provision of financial support in the framework of the PRODEX Programme of the European Space Agency (ESA). A.R.L. acknowledges support from a FONDECYT postdoctoral fellowship (3210157). The work of DS was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.We thank the referee for the suggestions and very detailed comments, which helped us improve the manuscript. We thank Teng Liu for his useful comments on our work. C.R. acknowledges support from Fondecyt Regular grant 1230345, ANID BASAL project FB210003, and the China-Chile joint research fund. M.J.T. acknowledges support from a FONDECYT postdoctoral fellowship (3220516). Y.D. acknowledges support from a FONDECYT postdoctoral fellowship (3230310). J.M.C.'s contribution was supported by an appointment to the NASA Postdoctoral Program at the NASA Goddard Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. R.R. acknowledges support from the Fundaci\u00F3n Jes\u00FAs Serra and the Instituto de Astrof\u00EDsica de Canarias under the Visiting Researcher Programme 2023\u20132025 agreed between both institutions. R.R. also acknowledges support from the ACIISI, Consejer\u00EDa de Econom\u00EDa, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2021010079, and the support through the RAVET project by the grant PID2019-107427GB-C32 from the Spanish Ministry of Science, Innovation and Universities MCIU. This work has also been supported through the IAC project TRACES, which is partially supported by the state budget and the regional budget of the Consejer\u00EDa de Econom\u00EDa, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community. RR also thanks to Conselho Nacional de Desenvolvimento Cient\u00EDfico e Tecnol\u00F3gico (CNPq, Proj. 311223/2020-6, 304927/2017-1 and 400352/2016-8), Funda\u00E7\u00E3o de amparo \u00E0 pesquisa do Rio Grande do Sul (FAPERGS, Proj. 16/2551-0000251-7 and 19/1750-2), Coordena\u00E7\u00E3o de Aperfei\u00E7oamento de Pessoal de N\u00EDvel Superior (CAPES, Proj. 0001). This work was funded by ANID through CATA-BASAL FB210003 (FEB); FONDECYT Regular 1200495 (FEB) and 1241005 (FEB); and Millennium Science Initiative AIM23-0001 and ICN12_009 (FEB). K.K.G. thanks the Belgian Federal Science Policy Office (BEL- SPO) for the provision of financial support in the framework of the PRODEX Programme of the European Space Agency (ESA). A.R.L. acknowledges support from a FONDECYT postdoctoral fellowship (3210157). The work of DS was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
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