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Example depiction of the importance of the alpha channel. When projected onto each other, the alpha channel allows the galaxies to appear as diffuse objects, hiding the sharp edges.
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![Figure 1. Comparison of Halo Mass to Stellar Mass relations from [19]...](publication/346120205/figure/fig1/AS:1021110313308171@1620463078674/Comparison-of-Halo-Mass-to-Stellar-Mass-relations-from-19-compared-to-21_Q320.jpg)
In this work we present “Astera’’, a cosmological visualization tool that renders a mock universe in real time using Unreal Engine 4. The large scale structure of the cosmic web is hard to visualize in two dimensions, and a 3D real time projection of this distribution allows for an unprecedented view of the large scale universe, with visually accur...
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... alpha channel was assigned in this case using the sum of the RGB layers, appropriately normalized "by eye" to appear visually realistic. The importance of this channel is demonstrated in Figure 4. Using this method, a few hundred distinct galaxies were extracted and processed from the SDSS dataset. ...
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... Data ingestion for simulations is not limited to terrain, and examples exist of how meteorological data can be imported to visualize real-time volumetric clouds using Python and Unreal Engine [34]. Researchers have gone beyond the earth and have even modeled real-time cosmological visualizations using Unreal Engine and galaxy image data [35]. Other rarer examples exist of actual simulators implemented such as a vehicle traffic simulator created in Unreal Engine [36]. ...
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One core aspect of immersive visualization labs is to develop and provide powerful tools and applications that allow for efficient analysis and exploration of scientific data. As the requirements for such applications are often diverse and complex, the same applies to the development process. This has led to a myriad of different tools, frameworks, and approaches that grew and developed over time. The steady advance of commercial off-the-shelf game engines such as Unreal Engine has made them a valuable option for development in immersive visualization labs. In this work, we share our experience of migrating to Unreal Engine as a primary developing environment for immersive visualization applications. We share our considerations on requirements, present use cases developed in our lab to communicate advantages and challenges experienced, discuss implications on our research and development environments, and aim to provide guidance for others within our community facing similar challenges.
To address the global warming problem, one of the space-based geoengineering solutions suggests the construction of an occluding disc that can work as a solar curtain to mitigate solar irradiation penetration to the earth atmosphere. A widely discussed concept needs the construction of a large-scale sunshade system near the Sun–Earth L1 equilibrium point in order to control the average global temperature. However, to improve the accuracy of theoretical estimations, more consistent modeling of the Sun-Curtain-Earth system and solar irradiance reduction rate are required. This study revisits the mathematical modeling of the solar irradiance reduction system and considers the fundamentals of shading physics. Simplified mathematical modeling of solar irradiance reduction rate is derived based on the solar flux density. For the climate control, controllability of the reduction rate by using some physical parameters (e.g., flux reflection rate and angle of the curtain) is discussed. Based on the results of this model, the technical challenges and feasibility of constructing a sunshade system at L1 Lagrange point are evaluated. Some technologically feasible, near-future options for the warming problem are discussed briefly.
One core aspect of immersive visualization labs is to develop and provide powerful tools and applications that allow for efficient analysis and exploration of scientific data. As the requirements for such applications are often diverse and complex, the same applies to the development process. This has led to a myriad of different tools, frameworks, and approaches that grew and developed over time. The steady advance of commercial off-the-shelf game engines such as Unreal Engine has made them a valuable option for development in immersive visualization labs. In this work, we share our experience of migrating to Unreal Engine as a primary developing environment for immersive visualization applications. We share our considerations on requirements, present use cases developed in our lab to communicate advantages and challenges experienced, discuss implications on our research and development environments, and aim to provide guidance for others within our community facing similar challenges.
The Universe at its largest scales remains still almost a mystery for most of the people not working in this field. With Astera, we present an educational video game that can teach about the cosmos whilst providing a thrilling and fun gaming experience. Astera allows the user to fly through the Universe up to the most distant galaxies, and “build” the Universe by growing and merging galaxies according to the most recent findings in astrophysics. As our results show, games like Astera can have a positive impact on players attitude towards galaxy evolution and science in general, and the player’s willingness to follow up on related activities.
Galaxy evolution is still relatively poorly understood. Specifically, star formation, mergers and the influence of a central supermassive black hole are all thought to be key drivers in regulating galaxy formation and evolution, but their relative contributions are not well constrained. Velocity dispersion ( σ ), a measure of the statistical variance of stellar motions in a galaxy, is known to be a key galaxy property, effectively tracing a galaxy’s gravitational potential well. The evolution of σ with cosmic time is also not well understood, despite having the potential to shed light on the relative importance of mergers versus star formation in building galaxies. σ is also known to be closely connected to the mass of the central supermassive black hole, via a tight correlation with slope of ∼ 4−6, which theories suggest could be a result of energetic winds/jets from active galactic nuclei (AGN) impacting onto the surrounding interstellar medium. In this work, I present a comprehensive semi-empirical approach to compute σ via detailed Jeans modelling, assuming, for the first time, both a constant and scale-dependent mass-to-light ratio M∗/L . I compare with a large sample of local galaxies from the MaNGA survey and find that both models can reproduce the Faber-Jackson relation and the weak dependence of σ with bulge-to-total ratio. I also explore the dynamical-to-stellar mass ratio within R ≲ Re , and show that the full dynamical mass within the effective radius can be fully accounted for by a gradient in M∗/L or a dark matter halo with an NFW profile. I then build velocity dispersion evolutionary histories, using the average histories of main progenitor dark matter haloes, assigning stellar masses, effective radii and Sersic indices via a variety of abundance matching, and empirically motivated relations. I find clear evidence for downsizing in velocity dispersion histories along the progenitor tracks, and a steady increase in velocity dispersion at fixed stellar mass with increasing redshift. I extract comparable velocity dispersion tracks from the TNG50 hydrodynamic simulation. The relative ‘flatness’ of these tracks is shown to be driven by the increasing dark matter fraction within Re , whilst showing a steeper evolution in the presence of a stellar gradient. I then show that a combination of mergers and internal star formation are likely responsible for the constant or increasing σap[ M∗,z ] with time. I then present new evidence for the fundamental nature of the relationship between black hole mass and σ, and show that my σ ap[ M∗, z ] tracks are consistent with a nearly constant and steep Mbh − σ relation at z ≲ 2, as predicted by AGN feedback models, with black hole masses derived from the LX − M∗ relation. I also show that AGN clustering can place new constraints on black hole-galaxy scaling relations, and explore the creation of AGN mock catalogs. Finally, I present an outcome of these mock catalogs, Astera, my cosmological visualization tool, which presents a real-time rendering of the large scale universe. Astera can represent an invaluable tool for survey planning and, due to its high user interactivity, also for gaming and educational and outreach activities.
Velocity dispersion (σ) is a key driver for galaxy structure and evolution. We here present a comprehensive semi-empirical approach to compute σ via detailed Jeans modelling assuming both a constant and scale-dependent mass-to-light ratio M*/L. We compare with a large sample of local galaxies from MaNGA and find that both models can reproduce the Faber-Jackson (FJ) relation and the weak dependence of σ on bulge-to-total ratio B/T (for B/T ≳ 0.25). The dynamical-to-stellar mass ratio within R ≲ Re can be fully accounted for by a gradient in M*/L. We then build velocity dispersion evolutionary tracks σap[M*, z] (within an aperture) along the main progenitor dark matter haloes assigning stellar masses, effective radii and Sérsic indices via a variety of abundance matching and empirically motivated relations. We find: 1) clear evidence for downsizing in σap[M*, z] along the progenitor tracks; 2) at fixed stellar mass σ∝(1 + z)0.2 − 0.3 depending on the presence or not of a gradient in M*/L. We extract σap[M*, z] from the TNG50 hydrodynamic simulation and find very similar results to our models with constant M*/L. The increasing dark matter fraction within Re tends to flatten the σap[M*, z] along the progenitors at z ≳ 1 in constant M*/L models, while σap[M*, z] have a steeper evolution in the presence of a stellar gradient. We then show that a combination of mergers and gas accretion are likely responsible for the constant or increasing σap[M*, z] with time. Finally, our σap[M*, z] are consistent with a nearly constant and steep Mbh − σ relation at z ≲ 2, with black hole masses derived from the LX − M* relation.
