Broadband X-ray Spectral Analysis of the Dual AGN System Mrk 739

Abstract

We present the result of a broadband (0.5-70 keV) X-ray spectral analysis of the late-merger galaxy Mrk 739, which contains a dual active galactic nucleus (AGN), Mrk 739E and Mrk 739W, with a separation of $\sim$3.4 kpc. The spectra obtained with NuSTAR, Chandra, XMM-Newton and Swift/BAT are simultaneously analyzed by separating the contributions from the two AGNs and extended emission with the Chandra data. To evaluate the reflection components from the AGN tori, we consider two models, a phenomenological one (pexrav and zgauss) and a more physically motivated one (XCLUMPY; Tanimoto et al. 2019). On the basis of the results with XCLUMPY, we find that the AGNs in Mrk 739E and Mrk 739W have intrinsic 2-10 keV luminosities of $1.0 \times 10^{43}$ and $7.5 \times 10^{41}\ \rm{erg}\ \rm{s}^{-1}$ absorbed by hydrogen column densities of $N_{\rm{H}} < 6.5 \times 10^{19}\ \rm{cm}^{-2}$ and $N_{\rm{H}} = 6.9^{+3.2}_{-1.7} \times 10^{21}\ \rm{cm}^{-2}$, respectively. The torus covering fraction of the material with $N_{\rm{H}} > 10^{22} \rm{cm}^{-2}$ in Mrk 739E, $C_{\rm{T}}^{(22)} < 0.50$ at a 90% confidence limit, is found to be smaller than those found for late-merger ultra/luminous infrared galaxies, $C_{\rm{T}}^{(22)} = 0.71\pm0.16$ (mean and standard deviation; Yamada et al. 2021). Considering the small star formation rate of Mrk 739E, we suggest that the gas-to-mass ratio of the host galaxy is an important parameter to determine the circumnuclear environment of an AGN in late merger.