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Abstract Cold Jovian planets play an important role in sculpting the dynamical environment in which inner terrestrial planets form. The core accretion model predicts that giant planets cannot form around low-mass M dwarfs, although this idea has been challenged by recent planet discoveries. Here, we investigate the occurrence rate of giant planets around low-mass (0.1–0.3M_⊙) M dwarfs. We monitor a volume-complete, inactive sample of 200 such stars located within 15 pc, collecting four high-resolution spectra of each M dwarf over six years and performing intensive follow-up monitoring of two candidate radial velocity variables. We use TRES on the 1.5 m telescope at the Fred Lawrence Whipple Observatory and CHIRON on the Cerro Tololo Inter-American Observatory 1.5 m telescope for our primary campaign, and MAROON-X on Gemini-North for high-precision follow up. We place a 95% confidence upper limit of 1.5% (68% confidence limit of 0.57%) on the occurrence ofM_Psini> 1M_Jgiant planets out to the water snow line and provide additional constraints on the giant planet population as a function ofM_Psiniand period. Beyond the snow line (100 K <T_eq< 150 K), we place 95% confidence upper limits of 1.5%, 1.7%, and 4.4% (68% confidence limits of 0.58%, 0.66%, and 1.7%) for 3M_J<M_Psini< 10M_J, 0.8M_J<M_Psini< 3M_J, and 0.3M_J<M_Psini< 0.8M_Jgiant planets, respectively; i.e., Jupiter analogs are rare around low-mass M dwarfs. In contrast, surveys of Sun-like stars have found that their giant planets are most common at these Jupiter-like instellations. 

Abstract We have observed thez= 4.3 protocluster SPT2349−56 with the Australia Telescope Compact Array (ATCA) with the aim of detecting radio-loud active galactic nuclei (AGNs) among the ∼30 submillimeter (submm) galaxies (SMGs) identified in the structure. We detect the central complex of submm sources at 2.2 GHz with a luminosity ofL_2.2= (4.42 ± 0.56) × 10²⁵W Hz⁻¹. MeerKAT and the Australian Square Kilometre Array Pathfinder also detect the source at 816 MHz and 888 MHz, respectively, constraining the radio spectral index toα= −1.45 ± 0.16, implyingL_1.4,rest= (2.2 ± 0.2) × 10²⁶W Hz⁻¹. The radio observations do not have sufficient spatial resolution to uniquely identify one of the three Atacama Large Millimeter/submillimeter Array (ALMA) galaxies as the AGN, however the ALMA source properties themselves suggest a likely host. This radio luminosity is ∼100× higher than expected from star formation, assuming the usual far-infrared–radio correlation, indicating an AGN driven by a forming brightest cluster galaxy. None of the SMGs in SPT2349−56 show signs of AGNs in any other diagnostics available to us, highlighting the radio continuum as a powerful probe of obscured AGNs. We compare these results to field samples of radio sources and SMGs, along with the 22 gravitationally lensed SPT-SMGs also observed in the ATCA program, as well as powerful radio galaxies at high redshifts. The (3.3 ± 0.7) × 10³⁸W of power from the radio-loud AGN sustained over 100 Myr is comparable to the binding energy of the gas mass of the central halo, and similar to the instantaneous energy injection from supernova feedback from the SMGs in the core region. The SPT2349−56 radio-loud AGNs may be providing strong feedback on a nascent intracluster medium.