A detailed study of the planetary nebula NGC 6565 has been carried out on long-slit echellograms ( \lambda / \Delta \lambda =60000 , spectral range= \lambda \lambda 3900–7750Å ) at six , equally spaced position angles .
The expansion velocity field , the c ( H \beta ) distribution and the radial profile of the physical conditions ( electron temperature and density ) are obtained .
The distance , radius , mass and filling factor of the nebula and the temperature and luminosity of the central star are derived .
The radial ionization structure is analyzed using both the classical method and the photo-ionization code CLOUDY .
Moreover , we present the spatial structure in a series of images from different directions , allowing the reader to “ see ” the nebula in 3-D. NGC 6565 results to be a young ( 2000–2500 years ) , patchy , optically thick triaxial ellipsoid ( a=10.1 arcsec , a/b=1.4 , a/c=1.7 ) projected almost pole-on .
The matter close to major axis was swept-up by some accelerating agent ( fast wind ?
ionization ?
magnetic fields ?
) , forming two faint and asymmetric polar cups .
A large cocoon of almost neutral gas completely embeds the ionized nebula .
NGC 6565 is in a recombination phase , because of the luminosity drop of the massive powering star , which is reaching the white dwarf domain ( logT _ { * } \simeq 5.08 K ; logL _ { * } /L _ { \odot } \simeq 2.0 ) .
The stellar decline started about 1000 years ago , but the main nebula remained optically thin for other 600 years before the recombination phase occurred .
In the near future the ionization front will re-grow , since the dilution factor due to the expansion will prevail on the slower and slower stellar decline .
NGC 6565 is at a distance of 2.0 ( \pm 0.5 ) Kpc and can be divided into three radial zones : the “ fully ionized ” one , extending up to 0.029–0.035 pc at the equator ( 0.050 pc at the poles ) , the “ transition ” one , up to 0.048–0.054 pc ( 0.080 pc ) , the “ halo ” , detectable up to 0.110 pc .
The ionized mass ( \simeq 0.03 M _ { \odot } ) is only a fraction of the total mass ( \geq 0.15 M _ { \odot } ) , which has been ejected by an equatorial enhanced superwind of 4 ( \pm 2 ) \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } lasted for 4 ( \pm 2 ) \times 10 ^ { 3 } years .