Accretion Properties of High- and Low-Excitation Young Radio Galaxies
  Young radio galaxies (YRGs) provide an ideal laboratory to explore the
connection between accretion disk and radio jet thanks to their recent jet
formation. We investigate the relationship between the emission-line
properties, the black hole accretion rate, and the radio properties using a
sample of 34 low-redshift (z < 0.4) YRGs. We classify YRGs as high-excitation
galaxies (HEGs) and low-excitation galaxies (LEGs) based on the flux ratio of
high-ionization to low-ionization emission lines. Using the H{\alpha}
luminosities as a proxy of accretion rate, we find that HEGs in YRGs have \sim1
dex higher Eddington ratios than LEGs in YRGs, suggesting that HEGs have higher
mass accretion rate or higher radiative efficiency than LEGs. In agreement with
previous studies, we find that the luminosities of emission lines, in
particular H{\alpha}, are correlated with radio core luminosity, suggesting
that accretion and young radio activities are fundamentally connected.
