EDP Sciences
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Volume 384, Number 2, March III 2002
Page(s) 603 - 619
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20011780

A&A 384, 603-619 (2002)
DOI: 10.1051/0004-6361:20011780

High resolution near-infrared spectro-imaging of NGC 7027

P. Cox1, P. J. Huggins2, J.-P. Maillard3, E. Habart1, C. Morisset4, R. Bachiller5 and T. Forveille6

1  Institut d'Astrophysique Spatiale, Bât. 121, Université de Paris XI, 91405 Orsay, France
2  Physics Department, New York University, 4 Washington Place, New York, NY 10003, USA
3  Institut d'Astrophysique de Paris, CNRS, 98b bd. Arago, 75014 Paris, France
4  Institut d'Astrophysique de Marseille, CNRS & Univ. de Provence, BP 8, 13376 Marseille Cedex 12, France
5  Observatorio Astronómico Nacional (IGN), Apt 1143, 28800 Alcalá de Henares, Spain
6  Observatoire de Grenoble, BP 53X, 38041 Grenoble Cedex, France

(Received 7 August 2001 / Accepted 5 December 2001 )

We present near-infrared spectro-imaging of the young planetary nebula NGC 7027 between 2.10 and 2.20  $\mu$m with high spatial (0.5 $^{\prime\prime}$) and high spectral ( $\rm 8.7 \, km \,
s^{-1}$ ) resolution. The observations, made using BEAR at the CFHT, reveal the detailed morphology and kinematics of the ionized nebula (in the Br $\gamma$ line and 16 other atomic lines) and the surrounding molecular envelope (in the 1-0 S(1) line of H 2). The observations show that the ionized gas forms an elongated ( ${\sim} 6
\arcsec\times 12\arcsec$ , ${\rm PA} = 32\degr$), limb-brightened shell with an expansion velocity of 19.5  along the line of sight. The shell is composed of numerous small condensations and has nearly parallel sides with flattened ends that are not well matched by a uniform ellipsoidal model. Low level Br $\gamma$ emission is detected at high red- and blue-shifted velocities ( $\pm 55$ ) along a bipolar axis at ${\rm PA} = 60\degr$ that deviates significantly from that of the main nebula. The $\rm H_2$ emission is distributed at the periphery of the ionized gas, in a limb-brightened, bi-conical shell ( ${\sim} 10\arcsec \times 13\arcsec$, ${\rm PA} = 28\degr$) with enhanced emission at the equator and complex structure at the ends of the major axis. The H 2 emission traces the inner edge of the extended molecular envelope seen in CO, and its distribution and intensity are well matched by model predictions of a high-density ( $n\rm _H \sim 10^6{-}10^5 \, cm^{-3}$) photo-dissociation region. The kinematic structure of the H 2 emission reveals a remarkable series of lobes and openings in the molecular shell. These features are point symmetric about the center, and the most prominent pair aligns with the high velocity, bipolar emission seen in Br $\gamma$. These observations demonstrate recent activity by collimated outflows in NGC 7027, with a multiple, bipolar geometry. The interaction of the outflows with the surrounding envelope has significantly affected the morphology of the developing nebula and its environment, and their presence in this well-studied archetype underscores the general importance of outflows in the early shaping history of planetary nebulae.

Key words: infrared: ISM -- ISM: lines and bands -- ISM: molecules -- planetary nebulae: general -- planetary nebulae: individual: NGC 7027

Offprint request: P. Cox, cox@ias.fr

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