3D Astrophysics Newsletter

2016_8_Hendrix5.8 Today´s new entry:

Pinwheels in the sky, with dust: 3D modeling of the Wolf-Rayet 98a environment

Tom Hendrix, Rony Keppens, Allard Jan van Marle, Peter Camps, Maarten Baes, Zakaria Meliani

Abstract: The Wolf-Rayet 98a (WR 98a) system is a prime target for interferometric surveys, since its identification as a “rotating pinwheel nebulae”, where infrared images display a spiral dust lane revolving with a 1.4 year periodicity. WR 98a hosts a WC9+OB star, and the presence of dust is puzzling given the extreme luminosities of Wolf-Rayet stars. We present 3D hydrodynamic models for WR 98a, where dust creation and redistribution are self-consistently incorporated. Our grid-adaptive simulations resolve details in the wind collision region at scales below one percent of the orbital separation (∼ 4 AU), while simulating up to 1300 AU. We cover several orbital periods under conditions where the gas component alone behaves adiabatic, or is subject to effective radiative cooling. In the adiabatic case, mixing between stellar winds is effective in a well-defined spiral pattern, where optimal conditions for dust creation are met. When radiative cooling is incorporated, the interaction gets dominated by thermal instabilities along the wind collision region, and dust concentrates in clumps and filaments in a volume-filling fashion, so WR 98a must obey close to adiabatic evolutions to demonstrate the rotating pinwheel structure. We mimic Keck, ALMA or future E-ELT observations and confront photometric long-term monitoring. We predict an asymmetry in the dust distribution between leading and trailing edge of the spiral, show that ALMA and E-ELT would be able to detect fine-structure in the spiral indicative of Kelvin-Helmholtz development, and confirm the variation in photometry due to the orientation. Historic Keck images are reproduced, but their resolution is insufficient to detect the details we predict.

Name of Publication: Monthly Notices of the Royal Astronomical Society (MNRAS)
URL of preprint: http://adsabs.harvard.edu/abs/2016arXiv160509239H
Accepted, doi: 10.1093/mnras/stw1289
Type of submission: Peer reviewed
Submitted by: Rony Keppens


3D Astrophysics – Why it fascinates me

3-D vision is beautiful, eye-popping and revealing. Also known as stereo vision, it can not only be helpful to better grasp the structure of a nebula, but also enhance our view of video games or … the horrors of past wars. Strangely, the latter is probably how I got hooked on 3-D visualization.

What have the actual remains of World War I battlefields to do with me writing a blog on 3-D astrophysics?


Stereogram of a 3-D model with four stars embedded in a dusty nebula with a jet from a young star. See the text for instruction on how to best view the image (modeled and rendered with SHAPE)

Continue reading

3D Astrophysics Newsletter


3-D model (right) of the Ant Nebula (Mz-3, left) by Clyne et al. (2015) 

5.7 Today´s new entry:

3-D structures of planetary nebulae

Wolfgang Steffen

Abstract: Recent advances in the 3-D reconstruction of planetary nebulae are reviewed. We include not only results for 3-D reconstructions, but also the current techniques in terms of general methods and software. In order to obtain more accurate reconstructions, we suggest to extend the widely used assumption of homologous nebula expansion to map spectroscopically measured velocity to position along the line of sight.

Name of Publication: Proceedings of the 11th Pacific Rim Conference held in Hong-Kong in Dec 2015, Sun Kwok (editor)
URL of preprint: http://arxiv.org/abs/1605.03082
8 pages, 3 figures,
Type of submission: Conference proceedings, review article
Submitted by: W. Steffen


3D Astrophysics Newsletter

2016_koribalski5.6 Today´s new entry:

The Local Universe: Galaxies in 3D

Baerbel S. Koribaliski

Abstract: Here I present results from individual galaxy studies and galaxy surveys in the Local Universe with particular emphasis on the spatially resolved properties of neutral hydrogen gas. The 3D nature of the data allows detailed studies of the galaxy morphology and kinematics, their relation to local and global star formation as well as galaxy environments. I use new 3D visualisation tools to present multi-wavelength data, aided by tilted-ring models of the warped galaxy disks. Many of the algorithms and tools currently under development are essential for the exploration of upcoming large survey data, but are also highly beneficial for the analysis of current galaxy surveys.

Name of Publication: Proceedings IAU Symposium No 309, 2014, CUP
URL of preprint: http://adsabs.harvard.edu/abs/2015IAUS..309…39K
8 pages, 4 figures
Type of submission: Conference proceedings
Submitted by: Baerbel Koribalski

Shaping photorealistic spacescapes


“The four Siblings”, a volumetric dusty reflection nebula with four young stars created in Shape.

It has become very fashionable for astrophotographers to go for the most beautiful and artistic celestial snapshot. The advent of highly sophisticated CCD equipment and software at affordable prices has made this possible over the last decade or so. The Astronomy Picture of the Day is a prime exhibition hall for many wonderful skyscapes that often leave us in awe as much as the best pictures from the Hubble Space Telescope.

For computational astrophysicists, these beautiful images are a strong source of motivation, maybe also of a slight bit of envy. While in numerical astrophysics visualization is an important topic, both for scientific analysis as well as for public outreach, images that look like the real thing are rather rare.


A different view of “The four Siblings”.

We have therefore been on a quest beyond science: develop our software Shape in such a way to be able to generate photorealistic images from scientific 3-D models. Now we couldn´t resist to share different views of a nebula that we recently modeled for testing purposes. The nebula could be called The four Siblings, because it contains four young stars still illuminating their dusty cradle, with one of them ejecting a powerful jet of gas from its accreting proto-stellar disk.

To obtain the images, four stars of different sizes and temperatures were embedded in a complex dust nebula.The dust distribution was generated using a 3-D noise texture. The jet and its bowshock are emission features. The background stars have been added using a new particle object type designed to generate more realistic nebula views.

While this 3-D model nebula is generic, the real challenge is, of course, producing scientifically acceptable and convincing looking models of actually existing nebulae. We are constantly developing and improving tools to make this a bit easier.

Watch this space…hopefully soon we can  present a movie with the camera flying around or into the nebula.

Wolfgang & Nico