2014A&A...563A..42R

Most spectroscopic studies of planetary nebulae (PNe) are based on data from specific parts of the objects. Considering the high complexity of their morphological structures, integrated or average values across an observed region can only provide limited information of their ionic, density, and temperature structures. We investigate the spatial variation of the physical and chemical properties of NGC 6302, a high-ionization PNe, with a complex bipolar structure. Spatially resolved long-slit spectroscopic data were obtained from 11 parallel and equally spaced directions over the nebula. Maps of emission line fluxes, line ratios, electron temperature T_e, electron density N_e, and ionic abundances (He⁺, He²⁺, N⁰, N⁺, O⁰, O⁺, O²⁺, S⁺, S²⁺, Ne²⁺, Ar²⁺, Ar³⁺, and Ar⁴⁺ relative to H⁺) were constructed with a spatial resolution of 1.45''x1'' for a large portion of the nebula over an area of 11''x250''. Electron densities were estimated from the [SII]λ6716/λ6731 and [ArIV]λ4711/λ4740 line ratios, and electron temperatures were estimated from the [OIII](λ4959+λ5007)/λ4363 and [NII](λ6548+λ6584)/λ5755 ratios. Integrated spectra were also obtained and 142 lines were identified. The electron density maps show a peaked distribution, with the densest area at the circumstellar region, reaching N_e≃40000cm^–3, and decreasing to N_e≤1000cm^–3 at the lobes. Knots were observed in the N_e (SII) map, with 2000cm^–3<N_e<3000cm^–3. The N_e (ArIV) map suggests the presence of an inner region with N_e≃20000cm^–3 that extends from the center through the east lobe. A homogeneous temperature distribution was found for both T_e(OIII) and T_e(NII). Small temperature fluctuations on the plane of the sky of t_s²(NII)=0.0071 and t_s²(OIII)=0.0043 were estimated. In general, the total abundances obtained are similar to the maximum found in the ionic abundance maps of the dominant ionic species. This demonstrates the potential of spatially resolved abundance studies for establishing lower limits of the total abundances based on ionic abundances, for checking the ionization correlation factors, and in some cases, for determining the total abundances directly from maps of ionic abundances.