Discovery of rare double-lobe radio galaxies hosted in spiral galaxies
  Double-lobe radio galaxies in the local Universe have traditionally been
found to be hosted in elliptical or lenticular galaxies. We report the
discovery of four spiral-host double-lobe radio galaxies (J0836+0532,
J1159+5820, J1352+3126 and J1649+2635) that are discovered by cross-matching a
large sample of 187005 spiral galaxies from SDSS DR7 to the full catalogues of
FIRST and NVSS. J0836+0532 is reported for the first time. The host galaxies
are forming stars at an average rate of 1.7 $-$ 10 M$_{\odot}$ yr$^{-1}$ and
possess Super Massive Black Holes (SMBHs) with masses of a few times 10$^{8}$
M$_{\odot}$. Their radio morphologies are similar to FR-II radio galaxies with
total projected linear sizes ranging from 86 kpc to 420 kpc, but their total
1.4 GHz radio luminosities are only in the range 10$^{24}$ $-$ 10$^{25}$ W
Hz$^{-1}$. We propose that the formation of spiral-host double-lobe radio
galaxies can be attributed to more than one factor, such as the occurrence of
strong interactions, mergers, and the presence of unusually massive SMBHs, such
that the spiral structures are not destroyed. Only one of our sources
(J1649+2635) is found in a cluster environment, indicating that processes other
than accretion through cooling flows e.g., galaxy-galaxy mergers or
interactions could be plausible scenarios for triggering radio-loud AGN
activity in spiral galaxies.
