Imaging the Elusive H-poor Gas in the High adf Planetary Nebula NGC 6778

García-Rojas, J.; Corradi, R. L. M.; Monteiro, H.; Jones, D.; Rodríguez-Gil, P.; Cabrera-Lavers, A.
Referencia bibliográfica

The Astrophysical Journal Letters, Volume 824, Issue 2, article id. L27, pp. (2016).

Fecha de publicación:
6
2016
Número de autores
6
Número de autores del IAC
5
Número de citas
52
Número de citas referidas
36
Descripción
We present the first direct image of the high-metallicity gas component in a planetary nebula (NGC 6778), taken with the OSIRIS Blue Tunable Filter centered on the O ii λ4649+50 Å optical recombination lines (ORLs) at the 10.4 m Gran Telescopio Canarias. We show that the emission of these faint O ii ORLs is concentrated in the central parts of the planetary nebula and is not spatially coincident either with emission coming from the bright [O iii] λ5007 Å collisionally excited line (CEL) or the bright Hα recombination line. From monochromatic emission line maps taken with VIMOS at the 8.2 m Very Large Telescope, we find that the spatial distribution of the emission from the auroral [O iii] λ4363 line resembles that of the O ii ORLs but differs from nebular [O iii] λ5007 CEL distribution, implying a temperature gradient inside the planetary nebula. The centrally peaked distribution of the O ii emission and the differences with the [O iii] and H i emission profiles are consistent with the presence of an H-poor gas whose origin may be linked to the binarity of the central star. However, determination of the spatial distribution of the ORLs and CELs in other PNe and a comparison of their dynamics are needed to further constrain the geometry and ejection mechanism of the metal-rich (H-poor) component and hence, understand the origin of the abundance discrepancy problem in PNe.