3D Astrophysics Newsletter

Neutral Hydrogen of an interacting galaxy pair seen in 3D

Neutral Hydrogen of an interacting galaxy pair seen in 3D (Punzo et al., 2015)

3.3 Today´s new entry:

The role of 3-D interactive visualization in blind surveys of HI in galaxies

D. Punzo, J.M. van der Hulst, J.B.T.M. Roerdink, T.A. Oosterloo, M. Ramatsoku, M.A.W. Verheijen

Abstract: Upcoming HI surveys will deliver large datasets, and automated processing using the full 3-D information (two positional dimensions and one spectral dimension) to find and characterize HI objects is imperative. In this context, visualization is an essential tool for enabling qualitative and quantitative human control on an automated source finding and analysis pipeline. We discuss how Visual Analytics, the combination of automated data processing and human reasoning, creativity and intuition, supported by interactive visualization, enables flexible and fast interaction with the 3-D data, helping the astronomer to deal with the analysis of complex sources. 3-D visualization, coupled to modeling, provides additional capabilities helping the discovery and analysis of subtle structures in the 3-D domain. The requirements for a fully interactive visualization tool are: coupled 1-D/2-D/3-D visualization, quantitative and comparative capabilities, combined with supervised semi-automated analysis. Moreover, the source code must have the following characteristics for enabling collaborative work: open, modular, well documented, and well maintained. We review four state of-the-art, 3-D visualization packages assessing their capabilities and feasibility for use in the case of 3-D astronomical data.

Journal: Astronomy and Computing
URL of preprint: http://arxiv.org/abs/1505.06976
Submitted by: Davide Punzo
Comments: Accepted on 25 May 2015, # 19 pages,  6 figures, 2 tabular.

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A different way of looking at the 3D universe

Constraining the 3D cosmic Web (Aragón et al., 2014)

Constraining the 3D cosmic Web (Aragón et al., 2014)

Miguel Aragón has his own way of looking the large scale universe, literally. He develops cutting edge 3D visualization techniques to get to new insight about the distribution and dynamics of galaxies from cosmological simulations. His visualizations are so unusual and revealing that they have featured on some of the top science outlets, such as the cover of Science and National Geographic and other documentaries. His work also won the 2011 Visualization Challenge. I had the chance to speak to him extensively during a visit of his here in Ensenada, which is just a few hours drive from Riverside where he is working. So he told me about the way he looks at 3D visualization as a tool for research in cosmology…me hoping to learn something that would help us in our own quest for better 3D simulations and visualizations of interstellar nebulae. One of the recurrent topics is, of course, how to constrain the third dimension. For more on Miguel´s work on this, read on…

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Front and back: The Pillars of Creation

The rough 3D structure of the "Pillars of Creation" in M16 according to Leod et al. (2015)

The rough 3D structure of the “Pillars of Creation” in M16 according to Leod et al. (2015)

A recent press release by the European Southern Observatory announced “Using the MUSE instrument on ESO’s Very Large Telescope (VLT), astronomers have produced the first complete three-dimensional view of the famous Pillars of Creation in the Eagle Nebula, Messier 16.” The corresponding scientific paper by Leod et al. (2015) is a very detailed analysis of the radiative structure of the nebula with the integral field spectrograph MUSE. One of their results is to decide the order in which the pillars are located along the line of sight. When there is no nice kinematic information that tells the structure, how do we know when parts of a nebula are closer or further away than others? How “complete” is the 3D view they produced? Read on to find out… Continue reading

3D Astrophysics Newsletter

Interactive 3D feature

Click on image to go to interactive 3D feature.

3.2 Today´s new entry:

Galaxy Interactions in Compact Groups II: abundance and kinematic anomalies in HCG 91c

F.P.A. Vogt, M.A. Dopita, S. Borthakur, L. Verdes-Montenegro, T.M. Heckman, M.S. Yun, K.C. Chambers

Abstract:
Galaxies in Hickson Compact Group 91 (HCG 91) were observed with the WiFeS integral field spectrograph as part of our ongoing campaign targeting the ionized gas physics and kinematics inside star forming members of compact groups. Here, we report the discovery of HII regions with abundance and kinematic offsets in the otherwise unremarkable star forming spiral HCG 91c. The optical emission line analysis of this galaxy reveals that at least three HII regions harbor an oxygen abundance ~0.15 dex lower than expected from their immediate surroundings and from the abundance gradient present in the inner regions of HCG 91c. The same star forming regions are also associated with a small kinematic offset in the form of a lag of 5-10 km/s with respect to the local circular rotation of the gas. HI observations of HCG 91 from the Very Large Array and broadband optical images from Pan-STARRS suggest that HCG 91c is caught early in its interaction with the other members of HCG 91. We discuss different scenarios to explain the origin of the peculiar star forming regions detected with WiFeS, and show that evidence point towards infalling and collapsing extra-planar gas clouds at the disk-halo interface, possibly as a consequence of long-range gravitational perturbations of HCG 91c from the other group members. As such, HCG 91c provides evidence that some of the perturbations possibly associated with the early phase of galaxy evolution in compact groups impact the star forming disk locally, and on sub-kpc scales.

Journal: Monthly Notices of the Royal Astronomical Society
Comments: MNRAS accepted, 25 pages, 21 figures. Until publication of the article, the interactive component of Figure 4 is available at this URLhttp://www.mso.anu.edu.au/~fvogt/website/misc.html
Submitted by: Frédéric Vogt

3D Astrophysics Newsletter

3D Spiral (Homan et al., 2015)

Position-velocity diagrams from a 3D-Spiral  (Homan et al., 2015)

3.1 Today´s new entry:

Simplified models of stellar wind anatomy for interpreting
high-resolution data

Analytical approach to embedded spiral geometries

W. Homan, L. Decin, A. de Koter, A.J. van Marle, R. Lombaert, W. Vlemmings

Abstract:
Context: Recent high-resolution observations have shown that stellar winds harbour complexities that strongly deviate from spherical symmetry, which generally is assumed as standard wind model. One such morphology is the Archimedean spiral, which is generally believed to be formed by binary interactions, as has been directly observed in multiple sources.
Aims: We seek to investigate the manifestation in the observables of spiral structures embedded in the spherical outflows of cool stars. We aim to provide an intuitive bedrock with which upcoming ALMA data can be compared and interpreted.
Methods: By means of an extended parameter study, we modelled rotational CO emission from the stellar outflow of asymptotic giant branch stars. To this end, we developed a simplified analytical parametrised description of a 3D spiral structure. This model is embedded into a spherical wind and fed into the 3D radiative transfer code LIME, which produces 3D intensity maps throughout velocity space. Subsequently, we investigated the spectral signature of rotational transitions of CO in the models, as well as the spatial aspect of this emission by means of wide-slit position-velocity (PV) diagrams. Additionally, we quantified the potential for misinterpreting the 3D data in a 1D context. Finally, we simulated ALMA observations to explore the effect of interefrometric noise and artefacts on the emission signatures.
Results: The spectral signatures of the CO rotational transition v=0 J=3-2 are very efficient at concealing the dual nature of the outflow. Only a select few parameter combinations allow for the spectral lines to disclose the presence of the spiral structure. If the spiral cannot be distinguished from the spherical signal, this might result in an incorrect interpretation in a 1D context. Consequently, erroneous mass-loss rates would be calculated. The magnitude of these errors is mainly confined to a factor of a few, but in extreme cases can exceed an order of magnitude. CO transitions of different rotationally excited levels show a characteristical evolution in their line shape that can be brought about by an embedded spiral structre. However, if spatial information on the source is also
available, the use of wide-slit PV diagrams systematically expose the embedded spiral. The PV diagrams also readily provide most of the geometrical and physical properties of the spiral-harbouring wind. Simulations of ALMA observations prove that the choice
of antenna configuration is strongly dependent on the geometrical properties of the spiral. We conclude that exploratory endeavours should observe the object of interest with a range of different maximum-baseline configurations.
Journal: Astronomy & Astrophysics
Submitted by: Ward Homan