The Spatial Orientation of Planetary Nebulae within the Milky Way

Weidmann, W. A.; Díaz, Rubén

doi:10.1086/587788

Cited by 10 publications

(25 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results are in agreement with Grinin & Zvereva (1968) and, since B is toroidal at low galactic latitudes, i.e. the field lies on the galactic plane, they are also in agreement with Melnick & Harwit (1975); Phillips (1997); Weidmann & Díaz (2008); Rees & Zijlstra (2013). At larger galactic radii and at high latitudes B is either weak or unrelated to the galactic plane, therefore we consider that our results also agree with Corradi, Aznar & Mampaso (1998).…”

Section: Discussionsupporting

confidence: 92%

On the alignment of PNe and local magnetic field at the Galactic centre: magnetohydrodynamical numerical simulations

Falceta‐Gonçalves

Monteiro

2014

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

For the past decade observations of the alignement of PNe symmetries with respect to the galactic disk have led to conflicting results. Recently the first direct observational evidence for a real alignment between PNe and local interstellar magnetic fields in the central part of the Galaxy (b < 5 • ) has been found. Motivated by the recent dicovery we studied the role of the interstellar magnetic field on the dynamical evolution of a planetary nebula by means of an analytical model and from 3D MHD numerical simulations. In our models the nebula is the result of a short-time event of mass ejection with its surrounding medium. The nebula asphericity is assumed to be due to an intrinsic shaping mechanism, dominated by the latitude-dependent AGB wind, and not the ISM field. We test under what conditions typical ejecta would have their dynamics severely modified by an interstellar magnetic field. We found that uniform fields of > 100µG are required in order to be dynamically dominant. This is found to occur only at later evolutionary stages, therefore being unable to change the general morphology of the nebula. However, the symmetry axis of bipolar and elliptical nebulae end up aligned to the external field. This result can explain why different samples of PNe result in different conclusions regarding the alignment of PNe. Objects located at high galactic latitudes, or at large radii, should present no preferential alignment with respect to the galactic plane. PNe located at the galactic centre and low latitudes would, on the other hand, be preferentiably aligned to the disk. Finally, we present synthetic polarization maps of the nebulae to show that the polarization vectors, as well as the field lines at the expanding shell, are not uniform even in the strongly magnetized case, indicating that polarization maps of nebulae are not adequate in probing the orientation, or intensity, of the dominant external field.

show abstract

Section: Discussionsupporting

confidence: 92%

On the alignment of PNe and local magnetic field at the Galactic centre: magnetohydrodynamical numerical simulations

Falceta‐Gonçalves

Monteiro

2014

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Shain 1956;Grinin & Zvereva 1968;Akhundova & Seidov 1970;Melnick & Harwit 1975;Phillips 1997;Corradi et al 1998;Weidmann & Díaz 2008). It provides information about mechanisms capable of explaining the various shapes of PNe such as bipolar and elliptical objects.…”

Section: The Galactic Orientation Of Ipnementioning

confidence: 99%

Interacting planetary nebulae

Ali

Sabin

Snaid

et al. 2012

A&A

View full text Add to dashboard Cite

We discuss the classification and orientation of planetary nebulae that interact with the interstellar medium throughout the Milky Way. A sample of 117 confirmed interacting planetary nebulae is used for this purpose. Our results indicate that the majority of interacting objects are located close to the Galactic plane, and ∼77% of them are located inside the Galactic thin disk. One third of the sample is less than 100 parsec from the Galactic plane and thus may interact with molecular and cold neutral clouds. There is a tendency for the planetary nebula interaction region to be parallel to the Galactic plane. We found that ∼73% of interacting planetary nebulae have inclination angles (defined as the angles that join the planetary nebula centroid and the interaction area or bow shock with the Galactic plane) larger than 45 • and ∼38% larger than 70 • , which highlights the possible effect of interstellar magnetic fields. While it is sometime believed that the interaction preferentially occurs in old planetary nebulae, our analysis indicates that the majority of observed planetary nebulae are in the mid stage of their evolution. The mean inclination angle, Galactic height, linear size, and dynamical age are estimated for each stage of interaction. The results indicate strong correlations between the mean inclination angle and the above parameters.

show abstract

“…There has been no convincing evidence for an alignment among nearby Galactic PNe, although there have been some claims for a preferential alignment of the polar axis with the Galactic plane (Melnick & Harwit 1975). The evidence of Weidmann & Díaz (2008) is based on a sample of 440 PNe that were either bipolar, or elliptical with a major to minor axis ratio greater than 1.2 : 1 of which 262 were in the direcc 0000 RAS tion of the Galactic centre. Within that group they found an excess of PNe with galactic position angle (GPA) ∼ 100 • .…”

Section: Introductionmentioning

confidence: 99%

Alignment of the angular momentum vectors of planetary nebulae in the Galactic Bulge

Rees

Zijlstra

2013

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We use high-resolution H α images of 130 planetary nebulae (PNe) to investigate whether there is a preferred orientation for PNe within the Galactic Bulge. The orientations of the full sample have an uniform distribution. However, at a significance level of 0.01, there is evidence for a non-uniform distribution for those planetary nebulae with evident bipolar morphology. If we assume that the bipolar PNe have an unimodal distribution of the polar axis in Galactic coordinates, the mean Galactic position angle is consistent with 90 • , i.e. along the Galactic plane, and the significance level is better than 0.001 (the equivalent of a 3.7σ significance level for a Gaussian distribution).The shapes of PNe are related to angular momentum of the original star or stellar system, where the long axis of the nebula measures the angular momentum vector. In old, low-mass stars, the angular momentum is largely in binary orbital motion. Consequently, the alignment of bipolar nebulae that we have found indicates that the orbital planes of the binary systems are oriented perpendicular to the Galactic plane. We propose that strong magnetic fields aligned along the Galactic plane acted during the original star formation process to slow the contraction of the star forming cloud in the direction perpendicular to the plane. This would have produced a propensity for wider binaries with higher angular momentum with orbital axes parallel to the Galactic plane. Our findings provide the first indication of a strong, organized magnetic field along the Galactic plane that impacted on the angular momentum vectors of the resulting stellar population.

show abstract

The Spatial Orientation of Planetary Nebulae within the Milky Way

Cited by 10 publications

References 15 publications

On the alignment of PNe and local magnetic field at the Galactic centre: magnetohydrodynamical numerical simulations

On the alignment of PNe and local magnetic field at the Galactic centre: magnetohydrodynamical numerical simulations

Interacting planetary nebulae

Alignment of the angular momentum vectors of planetary nebulae in the Galactic Bulge

Contact Info

Product

Resources

About