The structure of the compact planetary nebulae Cn 3-1 and M 3-27 and their extended haloes

Abstract

We present long-slit optical spectroscopy and VLA-B radio continuum (lambda = 3.6 cm) observations of the compact planetary nebulae Cn 3-1 and M 3-27, The data allow us to distinguish different regions in both objects, to study their kinematical and emission properties, and to deduce different physical parameters in both nebulae, The radio and optical data show that the ionized shell of Cn 3-1 is an ellipsoid containing a bright, ring-like equatorial zone (size similar or equal to 2.6 arcsec, expansion velocity similar or equal to 14 km s(-1)). Two bright, point-symmetric arcs have been detected in the core of Cn 3-1, extending from the equator towards the polar regions of the ellipsoid. The arcs seem to be filamentary structures located on the ellipsoid, The origin of the arcs could be related to some sort of collimated bipolar ejections along a rotating axis, Relatively high mean [N II]/H alpha similar or equal to 0.83 and [S II]/H alpha similar or equal to 0.056 line intensity ratios are found in Cn 3-1, Maximum values of [S II]/H alpha of similar or equal to 0.083 are found in the arcs. The estimated kinematical age and ionized mass of Cn 3-1 are similar or equal to 1300 yr and similar or equal to 4 x 10(-2) M., respectively. M 3-27 is unresolved at 3.6 cm (size less than or equal to 0.6 arcsec), The detected [N II] and [S II] emission lines arise in a compact (size less than or equal to 1.4 arcsec), probably non-spherical region, which is identified with the ionized shell of M 3-27, The Ha emission from M 3-27 is dominated by strong stellar emission and exhibits a type III P Cygni profile with very extended wings (similar or equal to 3000 km s(-1)). A kinematical age of less than or equal to 530 yr and an ionized mass of similar or equal to 3 x 10(-4) M. are estimated for M 3-27, Extended haloes (size similar or equal to 36 arcsec in Cn 3-1, similar or equal to 24 arcsec in M 3-27) have been spectroscopically detected in both objects through their [N II] and/or H alpha emissions, An analysis of the kinematical and emission properties of the haloes strongly suggests that they are reflection nebulosities and contain large amounts of neutral material, and that the distribution of neutral material in them is largely isotropic.