2019AJ....158..134M

Direct imaging surveys have discovered wide-orbit planetary-mass companions that challenge existing models of both star and planet formation, but their demographics remain poorly sampled. We have developed an automated binary companion point-spread function (PSF) fitting pipeline to take advantage of Spitzer's infrared sensitivity to planetary-mass objects and circum(sub)stellar disks, measuring photometry across the four Infrared Array Camera (IRAC) channels of 3.6, 4.5, 5.8, and 8.0 µm. We present PSF fitting photometry of archival Spitzer/IRAC images for 11 young, low-mass (M ∼ 0.044-0.88 M_☉; K3.5-M7.5) members of three nearby star-forming regions (Chameleon, Taurus, and Upper Scorpius; d ∼ 150 pc; τ ∼ 1-10 Myr) that host confirmed or candidate faint companions at ρ = 1.''68-7.''31. We recover all system primaries, six confirmed, and two candidate low-mass companions in our sample. We also measure nonphotospheric [3.6]-[8.0] colors for three of the system primaries, four of the confirmed companions, and one candidate companion, signifying the presence of circumstellar or circum(sub)stellar disks. We furthermore report the confirmation of a ρ = 4.''66 (540 au) companion to [SCH06] J0359+2009 which was previously identified as a candidate via imaging over five years ago, but was not studied further. Based on its brightness (M_[3.6] = 8.53 mag), we infer the companion mass to be M = 20 ± 5 M_Jup given the primary's model-derived age of 10 Myr. Our framework is sensitive to companions with masses less than 10 M_Jup at separations of ρ = 300 au in nearby star-forming regions, opening up a new regime of parameter space that has yet to be studied in detail, discovering planetary-mass companions in their birth environments and revealing their circum(sub)stellar disks.