The Compton-thick AGN population and the N H distribution of low-mass AGN in our cosmic backyard

Annuar, A; Alexander, D. M.; Gandhi, P.; Lansbury, G B; Rosli, M N; Stern, D; Asmus, D; Ballantyne, D R; Baloković, M; Bauer, F E; Boorman, P G; Brandt, W N; Brightman, M; Chen, C T J; Del Moro, A; Farrah, D; Harrison, F A; Koss, M J; Lanz, L; Marchesi, S; Mohanadas, P; Nardini, E; Ricci, C; Zappacosta, L

Abstract

We present a census of the Compton-thick (CT) active galactic nucleus (AGN) population and the column density () distribution of AGN in our cosmic backyard using a mid-infrared selected AGN sample within 15 Mpc. The column densities are measured from broad-band X-ray spectral analysis, mainly using data from Chandra and NuSTAR. Our sample probes AGN with intrinsic 2–10 keV luminosities of - erg s, reaching a parameter space inaccessible to more distant samples. We directly measure a 32 CT AGN fraction and obtain an distribution that agrees with that inferred by the Swift-BAT survey. Restricting the sample to the largely unexplored domain of low-luminosity AGN with , we found a CT fraction of , consistent with those observed at higher luminosities. Comparing the host-galaxy properties between the two samples, we find consistent star formation rates, though the majority of our galaxy have lower stellar masses (by dex). In contrast, the two samples have very different black hole mass () distributions, with our sample having 1.5 dex lower mean mass ( 10). Additionally, our sample contains a significantly higher number of LINERs and H ii-type nuclei. The Eddington ratio range probed by our sample, however, is the same as Swift-BAT, although the latter dominates at higher accretion rates, and our sample is more evenly distributed. The majority of our sample with 10 tend to be CT, while those with 10 are mostly unobscured or mildly obscured.

Citation

Annuar, A., Alexander, D. M., Gandhi, P., Lansbury, G. B., Rosli, M. N., Stern, D., Asmus, D., Ballantyne, D. R., Baloković, M., Bauer, F. E., Boorman, P. G., Brandt, W. N., Brightman, M., Chen, C. T. J., Del Moro, A., Farrah, D., Harrison, F. A., Koss, M. J., Lanz, L., Marchesi, S., …Zappacosta, L. (2025). The Compton-thick AGN population and the N H distribution of low-mass AGN in our cosmic backyard. Monthly Notices of the Royal Astronomical Society, 540(4), 3827-3849. https://doi.org/10.1093/mnras/staf956

• Journal Article Type: Article
• Acceptance Date: Jun 5, 2025
• Online Publication Date: Jun 14, 2025
• Publication Date: 2025-07
• Deposit Date: Jun 30, 2025
• Publicly Available Date: Jun 30, 2025
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 540
• Issue: 4
• Pages: 3827-3849
• DOI: https://doi.org/10.1093/mnras/staf956
• Keywords: galaxies: active, techniques: spectroscopic, X-rays: galaxies, galaxies: nuclei
• Public URL: https://durham-repository.worktribe.com/output/4125286