Keywords

We present a broadband (0.4–70 keV) X-ray spectral analysis of the luminous infrared galaxy (LIRG) system Mrk 463 observed with Nuclear Spectroscopic Telescope Array (NuSTAR), Chandra, and XMM-Newton, which contains double active galactic nuclei (AGNs; Mrk 463E and Mrk 463W) with a separation of ∼3.8 kpc. Detecting their transmitted hard X-ray >10 keV continua with NuSTAR, we confirm that Mrk 463E and Mrk 463W have AGNs with intrinsic luminosities of (1.6–2.2) × 10⁴³ and (0.5–0.6) × 10⁴³ erg s⁻¹ (2–10 keV) obscured by hydrogen column densities of 8 × 10²³ and 3 × 10²³ cm⁻², respectively. Both nuclei show strong reflection components from cold matter. The luminosity ratio between X-ray (2–10 keV) and [O iv] 25.89 μm of Mrk 463E is ∼5 times smaller than those of normal Seyfert galaxies, suggesting that the intrinsic SED is X-ray weak relative to the UV luminosity. In fact, the bolometric AGN luminosity of Mrk 463E estimated from L'-band (3.8 μm), [O iv] 25.89 μm, and [Ne v] 14.32 μm lines indicate a large bolometric-to-X-ray luminosity ratio, κ_{2–10 keV} ≈ 110–410, and a high Eddington ratio, λ_Edd ∼ 0.4–0.8. We suggest that the merger triggered a rapid growth of the black hole in Mrk 463E, which is not yet deeply "buried" by circumnuclear dust. By contrast, the L'-band luminosity of Mrk 463W is unusually small relative to the X-ray luminosity, suggesting that the Eddington ratio is low (<10⁻³) and it might be still in an early phase of merger-driven AGN activity.

We present optical and near-IR Integral Field Unit (IFU) and ALMA band 6 observations of the nearby dual active galactic nuclei (AGNs) Mrk 463. At a distance of 210 Mpc, and a nuclear separation of ∼4 kpc, Mrk 463 is an excellent laboratory to study the gas dynamics, star formation processes and supermassive black hole (SMBH) accretion in a late-stage gas-rich major galaxy merger. The IFU observations reveal a complex morphology, including tidal tails, star-forming clumps, and emission-line regions. The optical data, which map the full extent of the merger, show evidence for a biconical outflow and material outflowing at >600 km s⁻¹, both associated with the Mrk 463E nucleus, along with large-scale gradients likely related to the ongoing galaxy merger. We further find an emission-line region ∼11 kpc south of Mrk 463E that is consistent with photoionization by an AGN. Compared to the current AGN luminosity, the energy budget of the cloud implies a luminosity drop in Mrk 463E by a factor of 3–20 over the last 40,000 years. The ALMA observations of ¹²CO(2–1) and adjacent 1 mm continuum reveal the presence of ∼10⁹ M_☉ in molecular gas in the system. The molecular gas shows velocity gradients of ∼800 km s⁻¹ and ∼400 km s⁻¹ around the Mrk 463E and 463W nuclei, respectively. We conclude that, in this system, the infall of ∼100s M_⊙ yr⁻¹ of molecular gas is in rough balance with the removal of ionized gas by a biconical outflow being fueled by a relatively small, <0.01% of accretion onto each SMBH.