NIR Fabry-Perot Imaging Spectroscopy of PNe

Arias, L.; Rosado, M.

doi:10.1017/s0074180900208668

Cited by 4 publications

(6 citation statements)

References 6 publications

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“…The latter is known to be very strong in the NIR and MIR, with some evidence for weak extension to the north and south (see e.g. Zuckerman et al 1990; Arias & Rosado 2002; Rosado & Arias 2003; Hiriart 2005, and our discussion in ). It is also interesting to note that the edge of the elliptical envelope is very sharply defined, and forms a higher surface brightness annulus.…”

Section: Mir Mapping and Profiles For Ngc 6781mentioning

confidence: 69%

“…Levels of CO and H 2 emission appear to be extremely high compared to many other PNe, for instance (see e.g. Bachiller et al 1993; Bell et al 2007 for CO and CO + , and Zuckerman et al 1990; Arias & Rosado 2002; Rosado & Arias 2003; Hiriart 2005 for H 2 emission), whilst the ionized and molecular shells have similar dimensions and structures. There is also evidence that that H 2 S(1) emission extends slightly outside of the [N ii ] shell (e.g.…”

Section: Introductionmentioning

confidence: 88%

“…S(1)2–1/S(1)1–0 is typically ∼0.1–0.3 for shocks, and ∼0.5 for fluorescent excitation. This has been used to suggest that the NIR v = 1–0 transitions in NGC 6781 are shock excited, and used to determine total H 2 masses in the region of ∼0.09–0.4 M ⊙ (Arias & Rosado 2002; Rosado & Arias 2003; Hiriart 2005; see also Zuckerman et al 1990). However, it has also been noted that similarly low S(1)2–1/S(1)1–0 ratios can arise where UV excitation occurs in a dense nebular environment (Sternberg & Dalgarno 1989), so that this ratio is not the decisive parameter which has often been assumed in studies of this kind.…”

Section: The Excitation Temperature Of Molecular Hydrogenmentioning

confidence: 99%

“…Mavromatakis, Papamastorakis & Paleologou 2001; Rosado & Arias 2003), may imply that the source is similar to NGC 7026, and represents a bipolar outflow oriented nearly pole‐on to the line of sight (see e.g. Kastner et al 1994, 1996; Arias & Rosado 2002).…”

Section: Introductionmentioning

confidence: 99%

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Optical and mid-infrared observations of the planetary nebula NGC 6781

Phillips¹,

Ramos-Larios²,

Guerrero

2011

Monthly Notices of the Royal Astronomical Society

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Although the planetary nebula NGC 6781 appears to possess an elliptical morphology, its kinematic and emission characteristics are in many ways unusual, and it is possible that it may represent a bipolar source oriented close to the line of sight. We shall present deep imaging of this nebula in [O iii]λ5007, Hα and [N ii]λ6584, and using broad‐band (F555W and F814W) filters centred at λ8269 and λ5252. These were taken with the 2.56‐m Nordic Optical Telescope and Hubble Space Telescope. This is combined with mid‐infrared (MIR) imaging and spectroscopy acquired with the Spitzer Space Telescope (Spitzer), and near‐infrared spectroscopy deriving from the Infrared Space Observatory. These reveal details of the complex [N ii] structure associated with extended shell emission, perhaps associated with highly inclined bipolar lobes. We also note the presence of narrow absorbing filaments and clumps projected against the surface of the envelope, components which may be responsible for much of the molecular emission. We point out that such clumps may be responsible for complex source structure in the MIR, and give rise to asymmetries in emission along the major axis of the source. Although most of the MIR H2 v= 0–0 emission is clearly concentrated in the bright interior shell, we shall also find evidence for extended emission to the north and south, and determine rotational excitation temperatures of order ∼980 K.

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Section: Mir Mapping and Profiles For Ngc 6781mentioning

confidence: 69%

Section: Introductionmentioning

confidence: 88%

Section: The Excitation Temperature Of Molecular Hydrogenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optical and mid-infrared observations of the planetary nebula NGC 6781

Phillips¹,

Ramos-Larios²,

Guerrero

2011

Monthly Notices of the Royal Astronomical Society

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“…The expansion velocity of the [NII] is about 10 km s −1 (Arias & Rosado 2002). A typical velocity for the red giant wind of a carbon star is 12.5 km s −1 , as was determined by Olofsson et al (1993) based on CO observations.…”

Section: Molecular Hydrogen Kinematicsmentioning

confidence: 70%

Molecular hydrogen kinematics in the ring-like planetary nebula NGC 6781

Hiriart¹

2005

A&A

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Abstract. This paper presents the radial velocity mapping of the molecular hydrogen in the ring-like planetary nebula NGC 6781. Observations of the H 2 v = 1−0 S (1) emission line (2.122 µm, ∆λ = 0.02 µm) were obtained by Fabry-Pérot spectroscopy. These observations provide a very detailed map of the kinematic structure of the molecular hydrogen envelope in NGC 6781. The kinematic structure is explained with a model consisting of a thin hollow cylinder whose axis is tilted with respect to the line of sight, and gas expanding radially outward with a velocity proportional to the distance to the central star. Molecular hydrogen emission was detected at LSR velocities ranging from −6.2 to +57.1 km s −1 , with peak intensities between +15.7 and +25.5 km s −1 . There is evidence that the molecular hydrogen envelope is excited by shocks from the ionization front. The mass of molecular gas is estimated to be of the order of 0.2 M . The emergent picture from the H 2 kinematic structure supports the scenario where the structure of NGC 6781 was formed from the ionization and destruction of an ellipsoidal molecular envelope that began with the destruction and ionization of the least dense polar caps and will continue until the densest molecular material at nebular waist is fully ionized.

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