The radio spectra of reddened Two Micron All Sky Survey quasi-stellar objects: evidence for young radio jets

Abstract

Multifrequency radio continuum observations (1.4-22 GHz) of a sample of reddened quasi-stellar objects (QSOs) are presented. We find a high incidence (13/16) of radio spectral properties, such as low-frequency turnovers, high-frequency spectral breaks or steep power-law slopes, similar to those observed in powerful compact steep spectrum (CSS) and gigahertz-peaked spectrum (GPS) sources. The radio data are consistent with relatively young radio jets with synchrotron ages ? yr. This calculation is limited by the lack of high-resolution (milliarcsec) radio observations. For the one source in the sample that such data are available a much younger radio age is determined, ≲ 2 × 10³ yr, similar to those of GPS/CSS sources. These findings are consistent with claims that reddened QSOs are young systems captured at the first stages of the growth of their supermassive black holes. It also suggests that expanding radio lobes may be an important feedback mode at the early stages of the evolution of active galactic nuclei.