Keck HIRES Spectra of the Planetary Nebula NGC 7009

Abstract

With strategically important diagnostic lines of, e.g., [O II], [O III] and [S II], secured with the Keck I HIRES, we obtained electron densities and temperatures, while retaining 3-D spatial information for the well-known elliptical nebula NGC 7009: we found that the temperature fluctuations exceeded those reported in the HST imaging study, i.e. T_e ~9500 – 11500 K; we also found large velocity dispersions in the [S II] maps (with extremely high density fluctuations, i.e. log N_e = 3.8 – 4.5), but not in the [O II] ones. The [S II] map indicates that this emission is from numerous small-scale blobs of size ~ 1″ spread over a wider region, while [O II] shows no such evidence. The [S II] emission is likely to be due to shock excitation, while the [O II] emission is perhaps due to photoionization.