Near-infrared photometry of Galactic planetary nebulae with the VVV Survey

WEIDMANN, W.; GAMEN, R. C.; VAN HOOF, P.A.M.; ZIJLSTRA, A.; MINNITI, D.; VOLPE, M.G.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2013 vol. 552A p. 74 - 84

0004-6361

Context. Planetary nebulae (PNe) are powerful tracers of evolved stellar populations. Among the 3000 known PNe in the Galaxy,about 600 are located within the 520 square-degree area covered by the VVV survey. The VVV photometric catalogue provides animportant new dataset for the study of PNe, with high-resolution imaging in five near-infrared bands.Aims. There are various colour-colour diagrams that can be obtained from the VVV filters. We investigate the location of PNe in thesediagrams and the separation from other types of objects. This includes the new Y−J vs. Z−Y diagram.Methods. Aperture photometry of known PNe in the VVV area was retrieved from source catalogues. Care was taken to minimiseany confusion with field stars. The colours of the PNe we are determined for (H−Ks ), (J−H), (Z−Y), and (Y−J), and compared to starsand to other types of emission line objects. Cloudy photo-ionisation models were used to predict colours for typical PNe.Results. We present near-infrared photometry for 353 known PNe. The best separation from other objects is obtained in the (H−Ks )vs. (J−H) diagram. We calculated the emission-line contribution to the in-band flux based on a model for NGC 6720: we find thatthis is highest in the Z and Y bands at over 50%, lower in the J band at 40%, and lowest in the H and Ks bands at 20%. A new viewof PNe in the wavelength domain of the Z and Y bands is shown. Photo-ionisation models are used to explore the observed coloursin these bands. The Y band is shown to be dominated by He i 1.083 μm and He ii 1.012 μm, and colours involving this band are verysensitive to the temperature of the ionizing star.Conclusions. The VVV survey represents a unique dataset for studying crowded and obscured regions in the Galactic plane. Thediagnostic diagrams presented here allow one to study the properties of known PNe and to uncover objects not previously classified.