2022A&A...664A..39K

There are only five radio-loud quasars currently known within 1 Gyr from the Big Bang (z > 6) and the properties of their host galaxies have not been explored in detail. We present a NOrthern Extended Millimeter Array (NOEMA) survey of [CII] (158 µm) and underlying continuum emission of four z > 6 radio-loud quasars, revealing their diverse properties. J0309+2717 (z = 6.10) has a bright [CII] line and underlying continuum, implying that the host galaxy is a starburst with a star-formation rate SFR = 340-1200 M_☉/yr. J1429+5447 (z = 6.18) has a SFR = 520 - 870 M_☉/yr and its [CII] profile is consistent with two Gaussians, which could be interpreted as a galaxy merger. J1427+3312 (z = 6.12) has a moderate SFR = 30-90 M_☉/yr. Notably, this is a broad absorption line quasar and we searched for the presence of high-velocity outflows in the host galaxy. Although the NOEMA data tentatively reveal a broad component of the [CII] line as wide as ∼1400 km s^–1, the sensitivity of our current data are not sufficient to confirm it. Finally, P172+18 (z = 6.82) is undetected in both [CII] and the continuum, implying a SFR < 22-40 M_☉/yr. The broad range of SFRs is similar to what is observed in radio-quiet quasars at similar redshifts. If radio jets do not significantly contribute to both [CII] and IR luminosities, this suggests there is no feedback from the jet on the star formation in the host galaxy.