High resolution near-infrared spectro-imaging of NGC 7027

Abstract

Abstract. We present near-infrared spectro-imaging of the young planetary nebula NGC 7027 between 2.10 and 2.20 µm with high spatial (0.5 ) and high spectral (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 Brγ line and 16 other atomic lines) and the surrounding molecular envelope (in the 1-0 S(1) line of H2). The observations show that the ionized gas forms an elongated (∼6 × 12 , PA = 32• ), limb-brightened shell with an expansion velocity of 19.5 km s −1 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 Brγ emission is detected at high red-and blue-shifted velocities (±55 km s −1 ) along a bipolar axis at PA = 60• that deviates significantly from that of the main nebula. The H2 emission is distributed at the periphery of the ionized gas, in a limb-brightened, bi-conical shell (∼10 × 13 , PA = 28• ) with enhanced emission at the equator and complex structure at the ends of the major axis. The H2 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 (nH ∼ 10 6 −10 5 cm −3 ) photo-dissociation region. The kinematic structure of the H2 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 Brγ. 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.

On the Asymmetries of Extended X‐Ray Emission from Planetary Nebulae

“…7). Indeed, the morphology of high-velocity Br emission is very similar to that of the X-ray emission (Cox et al 2002). Similarly, both the optical emission and the diffuse soft X-ray emission from NGC 6543 appear to be point-symmetric (see Fig.…”

“…1 of KVS01). Emission from the X-rayemitting '' lobe '' projected northwest of the central star-a direction corresponding to blueshifted atomic and molecular gas (Cox et al 2002)-dominates the nebula in both the soft-and medium-band images. In the hard-band image, the emission is more balanced between the northwest (forwardfacing) and southeast (rearward-facing) X-ray lobes, and the northwest X-ray lobe has a smaller opening angle than in the medium-band image.…”

Binary planetary nebulae nuclei towards the Galactic bulge

“…Indeed, Kwok et al (2008) found excellent agreement between a narrowband H 2 image of NGC 6583 and the Spitzer IRAC band 4 image while demonstrating the bipolar (double-coned) morphology of NGC 6583. Another dramatic case where H 2 emission unambiguously identifies bipolar morphology not necessarily evident in optical emission lines can be seen in the velocity integrated H 2 image of NGC 7027 (Cox et al 2002).…”

High Dispersion Spectra of the Young Planetary Nebula NGC 7027

“…Note that the derived expansion velocity values are very different from those for the CO shell or photo-dissociation region. The CO or photo-dissociation emissions are prominent mostly along the bipolar axis (Fong et al, 2006;Cox et al, 2002). The kinematics of the major axis or the overall geometry involving the outer halo molecular zone is beyond the present study.…”

“…For example, Baines et al (2003) (Walsh et al, 1997), and 212 km s −1 (Ershov and Berulis, 1989). Fong et al (2006) derived the expansion velocity of 13-16 km s −1 in the CO shell, while Cox et al (2002) found an evidence of 55 km s −1 from the line widths in the photo-dissociation region along the bipolar axis. Such results derived by the earlier studies seem to disobey the general law for lines formed near the central star, such as [ArIV]: such high excitation lines usually march out slowly but those emitted in the outer zones, such as [N II], expand swiftly.…”