2023ApJ...945..121U

We report the multiwavelength properties of millimeter galaxies hosting X-ray detected active galactic nuclei (AGNs) from the ALMA Lensing Cluster Survey (ALCS). ALCS is an extensive survey of well-studied lensing clusters with ALMA, covering an area of 133 arcmin² over 33 clusters with a 1.2 mm flux-density limit of ∼60 μJy (1σ). Utilizing the archival data of Chandra, we identify three AGNs at z = 1.06, 2.09, and 2.84 among the 180 millimeter sources securely detected in the ALCS (of which 155 are inside the coverage of Chandra). The X-ray spectral analysis shows that two AGNs are not significantly absorbed ($\mathrm{log}{N}_{{\rm{H}}}/{\mathrm{cm}}^{-2}\lt 23$), while the other shows signs of moderate absorption ($\mathrm{log}{N}_{{\rm{H}}}/{\mathrm{cm}}^{-2}\sim 23.5$). We also perform spectral energy distribution modeling of X-ray to millimeter photometry. We find that our X-ray AGN sample shows both high mass-accretion rates (intrinsic 0.5-8 keV X-ray luminosities of ∼10^44–45 erg s^–1) and star formation rates (≳100 M_⊙ yr^–1). This demonstrates that a wide-area survey with ALMA and Chandra can selectively detect intense growth of both galaxies and supermassive black holes in the high-redshift universe.