NGC 4117: A New Compton-thick AGN Revealed by Broadband X-Ray Spectral Analysis

Pavithra Mohanadas and Adlyka Annuar


In this paper, we present the broadband (0.5–195 keV) X-ray spectral analysis for one of the newly detected AGNs in the Swift-BAT 105 month Hard X-ray Survey Catalog, NGC 4117. According to our ongoing research on low luminosity AGNs from the Swift-BAT 105 month catalog, we examine whether they are indeed low luminosity or heavily obscured AGNs. One of the AGNs in our sample is NGC 4117, where we discover it could be potentially a CTAGN. Therefore to examine NGC 4117 in detail, we combined the high energy Swift-BAT data with low energy data from XMM-Newton and Swift-XRT, and fitted the spectra simultaneously using physically-motivated models. A high absorption occurred at lower energies, i.e., below 3 keV. Past studies suggested that NGC 4117 was heavily obscured with a large column density (∼1023 cm−2). Our fitting suggests that this AGN is in the Compton-thick regime with a predicted line-of-sight column density (NH,los) of 3.82 × 1024 cm−2 and a torus column density (NH,tor) of 3.07 × 1024 cm−2. Both models yield intrinsic luminosity of 1.03 × 1042 erg s−1 at 2–10 keV while our bolometric luminosity is 2.05 × 1043 erg s−1, indicating that NGC 4117 is not an intrinsically low luminosity AGN. Rather, it is a standard AGN. The value of Eddington ratio that we obtained is 0.22, suggesting a very high accretion rate for this AGN.


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