2017MNRAS.465.1289A -
Mon. Not. R. Astron. Soc., 465, 1289-1296 (2017/February-3)
H2 in low-ionization structures of planetary nebulae.
AKRAS S., GONCALVES D.R. and RAMOS-LARIOS G.
Abstract (from CDS):
We report the detection of near-IR H2 emission from the low-ionization structures (knots) in two planetary nebulae. The deepest ever high-angular-resolution H2 (1-0) S(1) at 2.122 µm, H2 (2-1) S(1) at 2.248 µm and Brγ images of K 4-47 and NGC 7662, obtained using the Near InfraRed Imager and Spectrometer (NIRI) at Gemini-North, are analysed here. K 4-47 reveals a remarkable highly collimated bipolar structure not only in the optical but also in the molecular hydrogen emission. The H2 emission emanates from the walls of the bipolar outflows and also from the pair of knots at the tip of the outflows. The H2 (1-0) S(1)/(2-1) S(1) line ratio ranges from ∼7 to ∼10, suggesting the presence of shock interactions. Our findings can be explained by the interaction of a jet/bullet ejected from the central star with the surrounding asymptotic giant branch material. The strongest H2 line, (1-0) S(1), is also detected in several low-ionization knots located at the periphery of the elliptical planetary nebula NGC 7662, but only four of these knots are detected in the H2 (2-1) S(1) line. These four knots exhibit an H2 line ratio between 2 and 3.5, which suggests that the emission is caused by the UV ionizing flux of the central star. Our data confirm the presence of H2 gas in both fast- and slow-moving low-ionization knots, which has only been confirmed before in the nearby Helix nebula and Hu 1-2. Overall, the low-ionization structures of planetary nebulae are found to have similar traits to photodissociation regions.
Abstract Copyright:
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
ISM: molecules - planetary nebulae: general - planetary nebulae: individual: K 4-47 - planetary nebulae: individual: NGC 7662 - infrared: general - infrared: general
Simbad objects:
16
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2017MNRAS.465.1289A and select 'bookmark this link' or equivalent in the popup menu