Molecular Hydrogen Microstructures in Planetary Nebulae

Akras, S.; Gonçalves, Denise R.; Ramos-Larios, G.; Aleman, Isabel

doi:10.3390/galaxies8020030

Cited by 5 publications

(2 citation statements)

References 28 publications

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“…Most observational studies of jets report the spatial and kinematic properties in one single object or a small sample of sources (e.g., Balick et al 1987;Miranda & Solf 1992;Lopez et al 1993;Guerrero et al 1999;Corradi et al 2000;Akras & López 2012, among many others). Only a few studies have dealt with averaged properties for a sample of PNe, considering the morphological and kinematic properties (Gonçalves et al 2001;Akras & Gonçalves 2016) or the linear momenta of the jets (Tocknell et al 2014). The real space velocity of a jet could provide basic insights on its formation mechanisms and interactions with the nebular envelope, but it is unknown due to projection effects because the angle between the velocity vector and the line of sight cannot be determined.…”

Section: Introductionmentioning

confidence: 99%

Space Velocity and Time Span of Jets in Planetary Nebulae

Guerrero

Rechy-García

Ortiz

2020

ApJ

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Fast highly-collimated outflows including bipolar knots, jet-like features, and point-symmetric filaments or string of knots are common in planetary nebulae (PNe). These features, generally named as jets, are thought to play an active role in the nebular shaping immediately before or at the same time that fast stellar winds and D-type ionization fronts shock and sweep up the nebular envelope. The space velocity, radial distance from the central star and kinematic age of jets in PNe cannot be determined because the inclination angle with the line-of-sight is usually unknown. Here we have used the large number of jets already detected in PNe to derive orientation-independent properties from a statistical point of view. We find that jets in PNe can be assigned to two different populations: a significant fraction (≃70%) have space velocities below 100 km s −1 , whereas only ≃30% have larger velocities. Many jets move at velocities similar to that of their parent PNe and are found close to the nebular edge. We propose that these jets have been slowed down in their interaction with the nebular envelope, contributing to the expansion of their PN. The time span before a jet dissolves is found to be generally shorter than 2,500 yrs. Since most jets are found in young PNe of similar (1,000-3,000 yrs) age, it can be concluded that jets are mostly coeval with their PNe.

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Section: Introductionmentioning

confidence: 99%

Space Velocity and Time Span of Jets in Planetary Nebulae

Guerrero

Rechy-García

Ortiz

2020

ApJ

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“…Actually, recent observations have unveiled that LISs in PNe are also made of molecular hydrogen (H 2 ) (e.g., [15,16,[23][24][25]). These discoveries have provided a confirmation of the scenario proposed by [11] that LISs are dense molecular structures similar to the cometary knots of PNe like Helix and Dumbbell [26,27]; see Akras et al's contribution in [28]).…”

Section: Preliminary Results and Discussionmentioning

confidence: 52%

The Web of Micro-Structures in IC 4593

2020

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In addition to large-scale structures, planetary nebulae (PNe) show small-scale structures that emit mainly in low-ionization species such as [N ii], [S ii], [O ii], and [O i], known as LISs. Here, we present the analysis of optical long-slit spectra, for three slit positions, of the PN IC 4593, which possesses a pair of knots and an isolated low-ionization knot. The motivation for this work is the need to characterize LISs completely to evaluate their impact on the PNe studies. These data allow us to derive the physical properties and ionization state for each morphological component of the nebula, including its pair of knots and individual knot. Due to the large uncertainties in the [S ii] derived electron densities, we cannot confirm any contrast between the LISs’ electron densities and the surrounding nebula, found in numerous other LISs. Though the lack of spatially-resolved physical parameters in the literature prevents further comparisons, in general, our results derived for the entire nebula agree with previous studies.

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Detection of the [C I] λ8727 emission line

Akras,

Monteiro,

Walsh

et al. 2024

A&A

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We report the first spatially resolved detection of the near-infrared lambda 8727 emission from the outer pair of low-ionization structures (LISs) in the planetary nebula NGC 7009 from data obtained by the Multi Unit Spectroscopic Explorer (MUSE) integral field unit. This atomic carbon emission marks the transition zone between ionized and neutral gas and for the first time offers direct evidence that LISs are photodominated regions. The outer LIS pair exhibits intense lambda 8727 emission, but is absent. Conversely, the inner pair of knots shows both lines, likely due to the host nebula emission. Furthermore, the lambda 8727 line is absent in the host nebula emission, but lambda 8733 is present. Although the origin of the lambda 8727 line is still debated, its detection supports the scenario of photoevaporated dense molecular clumps.

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Molecular Hydrogen Microstructures in Planetary Nebulae

Cited by 5 publications

References 28 publications

Space Velocity and Time Span of Jets in Planetary Nebulae

Space Velocity and Time Span of Jets in Planetary Nebulae

The Web of Micro-Structures in IC 4593

Detection of the [C I] λ8727 emission line

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