Accretion/jet activity and narrow [O III] kinematics in young radio galaxies

We estimate black hole masses and Edenton ratios for a sample of 81 young radio galaxies, which includes 42 compact steep-spectrum (CSS) and 39 gigahertz-peaked spectrum (GPS) sources. We find that the average black hole (BH) mass of these young radio galaxies is 〈log Mbh〉 ∼8.3, which is less than that of radio loud QSOs and low redshift radio galaxies (〈log Mbh〉 ∼9.0). The CSS/GPS sources have relatively high Eddington ratios, with an average value of 〈log Lbol/LEdd〉 = −0.75, which are similar to those of narrow line Seyfert 1 galaxies (NLS1s). This suggests that young radio galaxies may not only be in the early stages of their radio activity, but also in the early stage of their accretion activity. We find that the young radio galaxies, as a class, systematically deviate from the Mbh-σ relation defined by nearby inactive galaxies, when using σ[O III] as a surrogate for stellar velocity dispersion σ. We also find that the deviation of the [O III] line width, Δσ =σ[O III]−σ[pred], is correlated with the Eddington ratio; sources with Lbol/LEdd∼1 have the largest deviations, which are similar to those of radio quiet QSOs/NLS1s (i.e., sources in which the radio jets are absent or weak), and where σ[pred] is calculated from the Tremaine et al. relation using our estimated BH masses. A similar result has been obtained for 9 linear radio Seyfert galaxies. On the basis of these results, we suggest that, in addition to the possible jet-gas interactions, accretion activities may also play an important role in shaping the kinematics of the narrow [O III] line in young radio galaxies.