Multiple outflows in the planetary nebula NGC 6058
  We present narrow-band [O III]lambda5007 and H-alpha images, as well as
long-slit high-resolution echelle spectra of the planetary nebula NGC 6058. Our
data reveal that NGC 6058 is a multipolar planetary nebula of about ~45 arcsec
in extent and formed by four bipolar outflows that are oriented at different
position angles. Assuming homologous expansion for all the structures, and a
distance of 3.5 kpc, we obtain polar velocities around ~68 km s^-1 for three of
them. The estimated kinematical ages suggest that the three oldest outflows
have been ejected in intervals of ~ 1100 and ~ 400 yr during which, the
ejection axis has changes its orientation by ~ 60 degrees and ~ 40 degrees,
respectively. Although a inner ring-like structure is suggested by the direct
images, its kinematics shows that no equatorial ring or toroid exists in the
nebula. At the contrary, the long-slit spectra reveal that the ring-like
structure corresponds to a fourth outflow that is oriented almost perpendicular
to the other three. This fourth outflow is the youngest one and appears to be
interacting with the other three, creating a protruding zone that sweeps
material in a region almost perpendicular to the major axes of the oldest
outflows. This structure also presents two bright arcuate regions along the
same direction of the older outflows, and at opposite sides from the central
star. From our model, we suggest that NGC 6058 could be anintermediate
evolutionary stage between starfish planetary nebulae and multipolar planetary
nebula with apparent equatorial lobes.
