2024/09/25 by M. Bierschenk, Bierschenk, M., C. Ricci +47
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2409.17334
openalex publication_date 2024/09/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We analyze the Spitzer spectra of 140 active galactic nuclei (AGN) detected in the hard X-rays (14-195 keV) by the Burst Alert Telescope (BAT) on board Swift. This sample allows us to probe several orders of magnitude in black hole masses (106-109 M\odot), Eddington ratios (10-3-1), X-ray luminosities (1042-1045\rm erg s-1), and X-ray column densities (1020-1024\rm cm-2). The AGN emission is expected to be the dominant source of ionizing photons with energies \gtrsim50 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 (\gtrsim85-90 per cent) for the mid-infrared 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 mid-infrared coronal line emission is driven by AGN activity. Interestingly, we find that the coronal lines are more tightly correlated to the bolometric luminosity (σ∼ 0.2-0.3 dex), calculated from careful analysis of the spectral energy distribution, than to the X-ray luminosity. We find that the relationship between the coronal line strengths and L14-150\rm keV is independent of black hole mass, Eddington ratio and X-ray column density. This confirms that the mid-infrared coronal lines can be used as unbiased tracers of the AGN power for X-ray luminosities in the 1042-1045\rm erg s-1 range.