Accretion/Jet Activity and Narrow [O III] Kinematics in Young Radio Galaxies

TL;DR

This study investigates the black hole properties, accretion activity, and narrow [O III] line kinematics in young radio galaxies, revealing early-stage accretion and deviations from the M_bh- relation linked to accretion activity.

Contribution

It provides the first comprehensive analysis of black hole masses, Eddington ratios, and [O III] kinematics in a sizable sample of young radio galaxies, highlighting the role of accretion in line kinematics.

Findings

Young radio galaxies have lower black hole masses than QSOs.

They exhibit high Eddington ratios similar to NLS1s.

[O III] line width deviations correlate with Eddington ratio.

Abstract

We estimate black hole masses and Eddington ratios for a sample of 81 young radio galaxies (42 CSS +39 GPS). 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. 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 deviate systematically from M_bh-\sigma relation defined by nearby inactive galaxies, when using [O III] as a surrogate for stellar velocity dispersion, \sigma_* . We also find that the deviation of the [O III] line width is correlated with the Eddington ratio and sources with Lbol/LEdd~1 have the largest deviations, which are similar to those of radio quiet QSOs/NLS1s (radio jets is absent or weak). 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 and linear radio Seyferts.