Nico Koning

PLANETARY NEBULAE DETECTED IN THE SPITZER SPACE TELESCOPE GLIMPSE LEGACY SURVEY

We detected and imaged 30 planetary nebulae in the Sptizer Space Telescope Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The distribution of warm dust is clearly shown in these images. From the derived fluxes at the 3.6, 4.5, 5.8, and 8.0 μm bands we are able to separate the photospheric, nebular, and dust emission components in the nebulae.

A wind–shell interaction model for multipolar planetary nebulae

We explore the formation of multipolar structures in planetary and pre-planetary nebulae from the interaction of a fast post-AGB wind with a highly inhomogeneous and filamentary shell structure assumed to form during the final phase of the high density wind. The simulations were performed with a new hydrodynamics code integrated in the interactive framework of the astrophysical modeling package SHAPE. In contrast to conventional astrophysical hydrodynamics software, the new code does not require any programming intervention by the user for setting up or controlling the code. Visualization and analysis of the simulation data has been done in SHAPE without external software. The key conclusion from the simulations is that secondary lobes in planetary nebulae, such as Hubble 5 and K3-17, can be formed through the interaction of a fast low-density wind with a complex high density environment, such as a filamentary circumstellar shell. The more complicated alternative explanation of intermittent collimated outflows that change direction, in many cases may therefore not be necessary. We consider that the wind-shell interaction scenario is more likely since the bow-shock shape expected from a strongly cooling bow-shock from jets is different from that of the observed bubbles. Furthermore, the timescales of the wind-wind interaction suggest that the progenitor star was rather massive.

THE TRUE SHAPES OF THE DUMBBELL AND THE RING

Using images centered around the 2.12 μm line of molecular hydrogen obtained with the Wide Field Infrared Camera on the Canada-France-Hawaii Telescope, we show that in spite of the different apparent morphologies, the Dumbbell Nebula and the Ring Nebula share the same intrinsic three-dimensional triple biconic structure.

Submillimeter array observation of the proto-planetary nebula CRL 618 in the CO J = 6-5 line

We report on the results of a Submillimeter Array (SMA) interferometric observation of the proto-planetary nebula CRL 618 in the 12CO J = 6-5 line. With the new capability of the SMA enabling us to use two receivers at a time, we also observed simultaneously in the 12CO J = 2-1 and 13CO J = 2-1 lines. The 12CO J = 6-5 and 13CO J = 2-1 lines were interferometrically observed for the first time toward CRL 618. The flux of the high-velocity component of the 12CO J = 6-5 line is almost fully recovered, while roughly 80% of the flux of the low-velocity component is resolved out. The low recovery rate suggests that the emission region of the low-velocity component of the 12CO J = 6-5 line is largely extended. Continuum emission is detected at both 230 and 690 GHz. The flux of the 690 GHz continuum emission seems to be partially resolved out, suggesting that dust emission partly contaminates the 690 GHz continuum flux. The cavity structure, which has been confirmed in a previous observation in the 12CO J = 2-1 line, is not clearly detected in the 12CO J = 6-5 line, and only the south wall of the cavity is detected. This result suggests that the physical condition of the molecular envelope of CRL 618 is not exactly axially symmetric.

Morphokinematic Properties of the 21 μm Source IRAS 07134+1005

We report the results of a Submillimeter Array (SMA) interferometric observation of 21 μm source IRAS 07134+1005 in the CO J = 3-2 line. In order to determine the morphokinematic properties of the molecular envelope of the object, we construct a model using the Shape software to model the observed CO map. We find that the molecular gas component of the envelopes can be interpreted as a geometrically thick expanding torus with an expanding velocity of 8 km s–1. The inner and outer radii of the torus determined by fitting Shape models are 12 and 30, respectively. The inner radius is consistent with the previous values determined by radiative transfer modeling of the spectral energy distribution and mid-infrared imaging of the dust component. The radii and expansion velocity of the torus suggest that the central star left the asymptotic giant branch about 1140-1710 years ago, and that the duration of the equatorial enhanced mass loss is about 2560-3130 years. From the absence of an observed jet, we suggest that the formation of a bipolar outflow may lag behind in time from the creation of the equatorial torus.

Hubble Space Telescope scale 3D simulations of MHD disc winds: a rotating two-component jet structure

We present the results of large scale, three-dimensional magneto-hydrodynamics simulations of disc-winds for different initial magnetic field configurations. The jets are followed from the source to 90 AU scale, which covers several pixels of HST images of nearby protostellar jets. Our simulations show that jets are heated along their length by many shocks. We compute the emission lines that are produced, and find excellent agreement with observations. The jet width is found to be between 20 and 30 AU while the maximum velocities perpendicular to the jet is found to be up to above 100 km/s. The initially less open magnetic field configuration simulations results in a wider, two-component jet; a cylindrically shaped outer jet surrounding a narrow and much faster, inner jet. These simulations preserve the underlying Keplerian rotation profile of the inner jet to large distances from the source. However, for the initially most open magnetic field configuration the kink mode creates a narrow corkscrew-like jet without a clear Keplerian rotation profile and even regions where we observe rotation opposite to the disc (counter-rotating). The RW Aur jet is narrow, indicating that the disc field in that case is very open meaning the jet can contain a counter-rotating component that we suggests explains why observations of rotation in this jet has given confusing results. Thus magnetized disc winds from underlying Keplerian discs can develop rotation profiles far down the jet that are not Keplerian.

THREE-DIMENSIONAL STRUCTURE OF THE CENTRAL REGION OF NGC 7027: A QUEST FOR TRAILS OF HIGH-VELOCITY JETS

We report on the results of a radio interferometric observation of NGC 7027 in the CO J = 2-1 and 13CO J = 2-1 lines. The results are analyzed with morpho-kinematic models developed from the software tool Shape. Our goal is to reveal the morpho-kinematic properties of the central region of the nebula, and to explore the nature of unseen high-velocity jets that may have created the characteristic structure of the central region consisting of molecular and ionized components. A simple ellipsoidal shell model explains the intensity distribution around the systemic velocity, but the high-velocity features deviate from the ellipsoidal model. Through the Shape automatic reconstruction model, we found a possible trail of a jet only in one direction, but no other possible holes were created by the passage of a jet.

AN OPTICAL-INFRARED STUDY OF THE YOUNG MULTIPOLAR PLANETARY NEBULA NGC 6644

High-resolution Hubble Space Telescope imaging of the compact planetary nebula NGC 6644 has revealed two pairs of bipolar lobes and a central ring lying close to the plane of the sky. From mid-infrared imaging obtained with the Gemini Telescope, we have found a dust torus which is oriented nearly perpendicular to one pair of the lobes. We suggest that NGC 6644 is a multipolar nebula and construct a three-dimensional model that allows the visualization of the object from different lines of sight. These results suggest that NGC 6644 may have similar intrinsic structures as other multipolar nebulae and the phenomenon of multipolar nebulosity may be more common than previously believed.

CO Structure of the 21 μm Source IRAS 22272+5435: A Sign of a Jet Launch?

We report the results of radio interferometric observations of the 21 μm source IRAS 22272+5435 in the CO J = 2-1 line. 21 μm sources are carbon-rich objects in the post-asymptotic-giant-branch phase of evolution, which show an unidentified emission feature at 21 μm. Since 21 μm sources usually also have circumstellar molecular envelopes, the mapping of CO emission from the envelope will be useful in tracing the nebular structure. From observations made with the Combined Array for Research in Millimeter-wave Astronomy, we find that a torus and spherical wind model can explain only part of the CO structure. An additional axisymmetric region created by the interaction between an invisible jet and ambient material is suggested.

Quark nova model for fast radio bursts

FRBs are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron stars light cylinder via