NuSTAR unveils a heavily obscured low-luminosity Active Galactic Nucleus in the Luminous Infrared Galaxy NGC 6286
C. Ricci, F. E. Bauer, E. Treister, C. Romero-Canizales, P. Arevalo, K. Iwasawa, G. C. Privon, D. B. Sanders, K. Schawinski, D. Stern, M. Imanishi
Abstract
We report the detection of a heavily obscured Active Galactic Nucleus (AGN) in the luminous infrared galaxy (LIRG) NGC 6286, identified in a 17.5 ks NuSTAR observation. The source is in an early merging stage, and was targeted as part of our ongoing NuSTAR campaign observing local luminous and ultra-luminous infrared galaxies in different merger stages. NGC 6286 is clearly detected above 10 keV and, by including the quasi-simultaneous Swift/XRT and archival XMM-Newton and Chandra data, we find that the source is heavily obscured [
N
H
≃(0.95−1.32)×
10
24
c
m
−2
], with a column density consistent with being Compton-thick [CT,
log(
N
H
/c
m
−2
)≥24
]. The AGN in NGC 6286 has a low absorption-corrected luminosity (
L
2−10keV
∼3−20×
10
41
erg
s
−1
) and contributes
≲
1\% to the energetics of the system. Because of its low-luminosity, previous observations carried out in the soft X-ray band (
<10
keV) and in the infrared did not notice the presence of a buried AGN. NGC 6286 has multi-wavelength characteristics typical of objects with the same infrared luminosity and in the same merger stage, which might imply that there is a significant population of obscured low-luminosity AGN in LIRGs that can only be detected by sensitive hard X-ray observations.