Revealing the Photodissociation Region:<i>HST</i>/NICMOS Imaging of NGC 7027

Latter, William B.; Dayal, Aditya; Bieging, John H.; Meakin, Casey; Hora, J. L.; Kelly, Douglas; Tielens, A. G. G. M.

doi:10.1086/309252

Cited by 97 publications

(145 citation statements)

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“…Aside from faint [O i] emission, the outer lobes are seen only in scattered light at visual wavelengths (Balick 1999). This structure, with [Fe ii] bulbs inside a thin H 2 skin, is similar to the double-shell structure in the nebula surrounding Car (Smith 2002 ( Welch et al 1999;Hora & Latter 1996) and NGC 7027 (Latter et al 2000). In HST images, the outer and inner shells of M2-9 distinguish themselves in low-and high-excitation emission lines like [O i] and [O iii], respectively (Balick 1999).…”

Section: Introductionsupporting

confidence: 57%

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9

Smith

Balick

Gehrz³

2005

Astron J

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We present new high-dispersion, long-slit, infrared (IR) spectra of the double-shell bipolar planetary nebula M2-9 in the emission lines [ Fe ii] k16435 and H 2 v ¼ 1 0 S(1) k21218. H 2 spectra reveal for the first time the kinematic structure of the outer shell in M2-9. Kinematics of the inner shell, traced by [Fe ii], resemble those of optical forbidden lines like [N ii] k6583, although we note subtle differences. [Fe ii] and H 2 shells have expansion speeds roughly proportional to distance from the star (''Hubble'' flows) and share the same dynamical age of 1200-2000 yr, depending on the distance to M2-9. Thus, the inner ionized lobes and outer molecular lobes, as well as the molecular torus and ''outer loops'' measured by other observers, were all formed around the same time. Consequently, their nested structure likely arises from an excitation gradient rather than independent ejections. H 2 and [Fe ii] emission is distributed more uniformly than [N ii], and IR lines are not dominated by the moving ionization pattern like visualwavelength lines. We suggest that this is because IR lines of [Fe ii] and H 2 are excited by relatively isotropic far-UV radiation (Balmer continuum), whereas optical lines respond to a directed rotating beam of Lyman continuum. Finally, we highlight intriguing similarities between M2-9 and the Homunculus of Car, despite the different central engines powering the two nebulae.

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Section: Introductionsupporting

confidence: 57%

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9

Smith

Balick

Gehrz³

2005

Astron J

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“…Morphologically, NGC 7027 consist of a bright rim-like structure with an attached faint shell, surrounded by a molecular shell seen in emission from H 2 (Latter et al 2000, Fig. 7 therein).…”

Section: Ngc 7027mentioning

confidence: 99%

The evolution of planetary nebulae

Schönberner

Jacob

Steffen

2005

A&A

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Abstract.A detailed theoretical study of the basic internal kinematics of planetary nebulae is presented, based on 1D radiationhydrodynamics simulations of circumstellar envelopes around central stars of 0.595 and 0.696 M . By means of observable quantities like radial surface-brightness distributions and emission-line profiles computed from the models, a comparison with real objects was performed and revealed a reasonable agreement. This allowed to draw important conclusions by investigating the kinematics of these models in detail. Firstly, it is shown that the determination of kinematical ages, normally considered to be simple if size and expansion rate of an object are given, can seriously be flawed. Secondly, the expansion law of a planetary nebula is different from what is assumed for deriving spatio-kinematical models. Thirdly and most importantly, our hydrodynamical models help to correctly use existing angular expansion measurements for distance determinations. The mere combination of the angular expansion rates with the spectroscopic expansion velocities leads always to a serious underestimate of the distance, the degree of which depends on the evolutionary state of the object. The necessary correction factor varies between 3 and 1.3. Individual correction factors can be estimated with an accuracy of about 10% by matching our hydrodynamical models to real objects. As a result, revised distances for a few objects with reliable angular expansion rates are presented. But even these corrected distances are not always satisfying: they still appear to be inconsistent with other distance determinations and, even more disturbing, with the accepted theory of post-asymptotic giant branch evolution. As a byproduct of the angular expansion measurements, the transition times from the vicinity of the asymptotic giant branch to the planetary-nebula regime could be estimated. They appear to be shorter than assumed in the present evolutionary calculations.

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“…1a). The core region clearly suffers a large degree of spatially irregular (clumpy) extinction in the optical, whereas, in the near-infrared (Kastner et al 1994;Latter et al 2000, hereafter L2000) and radio (Masson 1989), the ionized region is revealed to be an elliptical shell. Surrounding this shell, but largely interior to the system of concentric rings, is a photodissociation region with a remarkable cloverleaf or double-ring morphology that is best seen in near-infrared H 2 and polycyclic aromatic hydrocarbon emission (Graham et al 1993;Kastner et al 1996;L2000).…”

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confidence: 99%

Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL]

Kastner

Vrtilek

Soker

2001

The Astrophysical Journal

116

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We report the discovery of X-ray emission from NGC 7027, a prototypical object for the study of the formation and evolution of planetary nebulae. Observations with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-Ray Observatory show that the X-ray emission from NGC 7027 is extended and is bipolar in morphology. The ACIS spectrum displays strong emission from highly ionized Ne and weaker emission features, which we attribute to O, Mg, and Si. Model fits to this spectrum suggest a characteristic temperature T ∼ 3 # X K and an intrinsic (unabsorbed) X-ray luminosity of ergs s Ϫ1 . The intranebular absorption of 6 32 10 L ∼ 1.3 # 10 X X-ray emission is highly nonuniform, but the modeling indicates an average column density cm Ϫ2 , 21 N ∼ 6 # 10 H consistent with previous measurements of relatively large visual extinction within the nebula. We suggest that the X-ray emission from NGC 7027 is or was generated by a hitherto undetected fast wind from the central star of NGC 7027 or from a companion to this star. Chandra's detection of extended, high-temperature X-ray emission from BD ϩ30Њ3639, NGC 6543, and now NGC 7027 suggests that such emission is a common feature of young planetary nebulae.

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Revealing the Photodissociation Region:HST/NICMOS Imaging of NGC 7027

Cited by 97 publications

References 50 publications

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9

The evolution of planetary nebulae

Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL]

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Revealing the Photodissociation Region:HST/NICMOS Imaging of NGC 7027

Cited by 97 publications

References 50 publications

Kinematic Structure of H2and [Feii] in the Bipolar Planetary Nebula M2-9

Kinematic Structure of H2and [Feii] in the Bipolar Planetary Nebula M2-9

The evolution of planetary nebulae

Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL]

Contact Info

Product

Resources

About

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9

Kinematic Structure of H₂and [Feii] in the Bipolar Planetary Nebula M2-9