3D Astrophysics Newsletter

9.7 Today´s new entry:

2018_garcia-diazThe Owl and other strigiform nebulae: multipolar cavities within a filled shell

Ma. T. García-Díaz, W. Steffen, W. J. Henney, J. A. López, F. García-López, D. González-Buitrago and A. Áviles

Abstract: We present the results of long-slit echelle spectroscopy and deep narrow-band imaging of the Owl Nebula (NGC 3587), obtained at the Observatorio Astronómico Nacional, San Pedro Mártir. These data allow us to construct an iso-velocity data cube and develop a 3-D morpho-kinematic model. We find that, instead of the previously assumed bipolar dumbbell shape, the inner cavity consists of multi-polar fingers within an overall tripolar structure. We identify three additional planetary nebulae that show very similar morphologies and kinematics to the Owl, and propose that these constitute a new class of strigiform (owl-like) nebulae. Common characteristics of the strigiform nebulae include a double-shell (thin outside thick) structure, low-luminosity and high-gravity central stars, the absence of a present-day stellar wind, and asymmetric inner cavities, visible in both optical and mid-infrared emission lines, that show no evidence for surrounding bright rims. The origin of the cavities is unclear, but they may constitute relics of an earlier stage of evolution when the stellar wind was active.

Journal: Monthly Notices of the Royal Astronomical Society (MNRAS), in press
URL of preprint: here
Submitted by: Wolfgang Steffen


3D Astrophysics Newsletter

2018_kaminski9.6 Today´s new entry:

Submillimeter-wave emission of three Galactic red novae:
cool molecular outflows produced by stellar mergers

T. Kaminski, W. Steffen, R. Tylenda, K.H. Young, N.A. Patel, K.M. Menten

Abstract: Red novae are optical transients erupting at luminosities typically higher than those of classical novae. Their outbursts are believed to be caused by stellar mergers. We present millimeter/submillimeter-wave observations with ALMA and SMA of the three best known Galactic red novae, V4332 Sgr, V1309 Sco, and V838 Mon. The observations were taken 22, 8, and 14 yr after their respective eruptions and reveal the presence of molecular gas at excitation temperatures of 35–200 K. The gas displays molecular emission in rotational transitions with very broad lines (full width 400 km s􀀀1). We found emission of CO, SiO, SO, SO2 (in all three red novae), H2S (covered only in V838 Mon) and AlO (present in V4332 Sgr and V1309 Sco). No anomalies were found in the isotopic composition of the molecular material and the chemical (molecular) compositions of the three red novae appear similar to those of oxygen-rich envelopes of classical evolved stars (RSGs, AGBs, post-AGBs). The minimum masses of the molecular material that most likely was dispersed in the red-nova eruptions are 0.05, 0.01, and 10􀀀4 M for V838 Mon, V4332 Sgr, and V1309 Sco, respectively. The molecular outflows in V4332 Sgr and V1309 Sco are spatially resolved and appear bipolar. The kinematic distances to V1309 Sco and V4332 Sgr are 2.1 and 4.2 kpc, respectively. The kinetic energy stored in the ejecta of the two older red-nova remnants of V838 Mon and V4332 Sgr is of order 1046 erg, similar to values found for some post-AGB (pre-PN) objects whose bipolar ejecta were also formed in a short-duration eruption. Our observations strengthen the link between these post-AGB objects and red novae and support the hypothesis that some of the post-AGB objects were formed in a common-envelope ejection event or its most catastrophic outcome, a merger.

Journal: Astronomy and Astrophysics, in press
URL of preprint: 2018arXiv180401610K
Submitted by: T. Kaminski

The 3D Astrophysics Newsletter

agiantsingin.gif9.5 Today´s new entry:

Magnetic Seismology of Interstellar Gas Clouds: Unveiling a Hidden Dimension

Aris Tritsis, Konstantinos Tassis

Abstract: Stars and planets are formed inside dense interstellar molecular clouds, by processes imprinted on the 3-dimensional (3D) morphology of the clouds. Determining the 3D structure of interstellar clouds remains challenging, due to projection effects and difficulties measuring their extent along the line of sight. We report the detection of normal vibrational modes in the isolated interstellar cloud Musca, allowing determination of the 3D physical dimensions of the cloud. Musca is found to be vibrating globally, with the characteristic modes of a sheet viewed edge-on, not a filament as previously supposed. We reconstruct the physical properties of Musca through 3D magnetohydrodynamic simulations, reproducing the observed normal modes and confirming a sheet-like morphology.

Journal: Science
URL of preprint: https://arxiv.org/pdf/1805.03664.pdf
Comments: accepted 14 March 2018, 24 pages, 8 figures

3D Astrophysics Newsletter

2018_Izquierdo9.4 Today´s new entry:

Radiative transfer modelling of W33A MM1: 3-D structure and dynamics of a complex massive star forming region

Andres F. Izquierdo, Roberto Galván-Madrid, Luke T. Maud, Melvin G. Hoare, Katharine G. Johnston, Eric R. Keto, Qizhou Zhang, Willem-Jan de Wit

Abstract: We present a composite model and radiative transfer simulations of the massive star forming core W33A MM1. The model was tailored to reproduce the complex features observed with ALMA at $\approx 0.2$ arcsec resolution in CH$_3$CN and dust emission.
The MM1 core is fragmented into six compact sources coexisting within $\sim 1000$ au. In our models, three of these compact sources are better represented as disc-envelope systems around a central (proto)star, two as envelopes with a central object, and one as a pure envelope. The model of the most prominent object (Main) contains the most massive (proto)star ($M_\star\approx7~M_\odot$) and disc+envelope ($M_\mathrm{gas}\approx0.4~M_\odot$), and is the most luminous ($L_\mathrm{Main} \sim 10^4~L_\odot$). The model discs are small (a few hundred au) for all sources.
The composite model shows that the elongated spiral-like feature converging to the MM1 core can be convincingly interpreted as a filamentary accretion flow that feeds the rising stellar system. The kinematics of this filament is reproduced by a parabolic trajectory with focus at the center of mass of the region. Radial collapse and fragmentation within this filament, as well as smaller filamentary flows between pairs of sources are proposed to exist.
Our modelling supports an interpretation where what was once considered as a single massive star with a $\sim 10^3$ au disc and envelope, is instead a forming stellar association which appears to be virialized and to form several low-mass stars per high-mass object.

Journal: Monthly Notices of the Royal Astronomical Society
URL of preprint: https://arxiv.org/abs/1804.09204
Comments : 22 pages, 13 figures, 3 tables. Accepted on April 20, 2018
Submitted by: Andres Izquierdo

3D Astrophysics Newsletter

2018_Pachoulakis9.3 Today´s new entry:

Realistic Multimedia Tools based on Physical Models: II. The Binary 3D Renderer (B3dR)

I. Pachoulakis

Abstract: The present article reports on the second tool of a custom-built toolkit intended to train astronomers into simulating and visualizing the composite 3D structure of winds from hot close double stars by implementing a technique which is similar to multi-directional medical tomography. The flagships of the toolkit are the Spectrum Analyzer and Animator (SA 2) and the Binary 3D Renderer (B3dR). Following application of the first tool, SA 2 as detailed in paper I, the composite wind structure of the binary has been recovered and the B3dR is subsequently employed to visualize the results and simulate the revolution of the entire system (stars, winds and wind-interaction effects) around the common centre of mass. The B3dR thus repackages the end product of a lengthy physical modeling process to generate realistic multimedia content and enable the presentation of the 3D system from the point of view of an observer on Earth as well as from any other observer location in the Galaxy.

Publication: 2008 International Conference on Telecommunications and Multimedia (TEMU’08), Ierapetra, Crete, Greece
URL of preprint: https://arxiv.org/abs/1805.00211
Submitted by:
 Ioannis Pachoulakis

3D Astrophysics Newsletter

2018_dykes9.2 Today´s new entry

Interactive 3D Visualization for Theoretical Virtual Observatories

Tim Dykes, Amr Hassan, Claudio Gheller, Darren Croton, Mel Krokos

Abstract: Virtual Observatories (VOs) are online hubs of scientific knowledge. They encompass a collection of platforms dedicated to the storage and dissemination of astronomical data, from simple data archives to e-research platforms offering advanced tools for data exploration and analysis. Whilst the more mature platforms within VOs primarily serve the observational community, there are also services fulfilling a similar role for theoretical data. Scientific visualization can be an effective tool for analysis and exploration of datasets made accessible through web platforms for theoretical data, which often contain spatial dimensions and properties inherently suitable for visualization via e.g. mock imaging in 2d or volume rendering in 3d. We analyze the current state of 3d visualization for big theoretical astronomical datasets through scientific web portals and virtual observatory services. We discuss some of the challenges for interactive 3d visualization and how it can augment the workflow of users in a virtual observatory context. Finally we showcase a lightweight client-server visualization tool for particle-based datasets allowing quantitative visualization via data filtering, highlighting two example use cases within the Theoretical Astrophysical Observatory.

Journal: Monthly Notices of the Royal Astronomical Society
URL of preprint: https://arxiv.org/abs/1803.11399
Comments: Accepted for publication 28/03/18
Submitted by: Tim Dykes

3D Perception in Astronomy

Dear Friends of 3D Astronomy,

as we have discussed earlier in this blog, spatial perception of astronomical imagery is more difficult than in our everyday surrounding, since there are fewer cues to 3D information that our brain can process to obtain spatial information.

There is surprisingly little research on this subject and we would like change that. But we need your help! To improve on this situation we have developed a questionnaire as starting point to better understand 3D perception of astronomical objects and hopefully will help the astronomical community to produce more effective visualizations for outreach and research.

To participate we invite you to select ONE of the following two links to the online questionnaires. It will take approximately 20-30 minutes of your time to complete the 15 questions.


Please feel free to share this message with friends and family. Every reply helps!
We very much value your contribution and thank you for the time invested.

All the best,

Urban Eriksson (University of Lund, Sweden)
Wolfgang Steffen (Institute of Astronomy, UNAM, Mexico)