Vislab Research

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MeerKAT discovers mystery clouds

G. Jozsa, M.E. Cluver, T.H. Jarrett,  et al.

Type: Press Release
An international team led by astronomers Gyula Jozsa, Michelle Cluver, and Thomas Jarrett has utilized the South African MeerKAT telescope to discover a mysterious chain of hydrogen gas clouds the size of a massive galaxy. The accumulation of elemental hydrogen without associated stellar components is the largest yet discovered. It is found close to, or within, a gravitationally-bound group of galaxies in a cosmic filament

Paper Press Release: Astronomers reveal cosmic ribbon around rare galaxy

N. Deg, R. Palleske, K. Spekkens, et al.

Type: Press Release; Paper
A team of international astronomers, including those from the University of Cape Town (UCT) and Queen’s University, have revealed a galaxy wrapped in a cosmic ‘ribbon’ using a telescope owned and operated by CSIRO, Australia’s national science agency. Published in Monthly Notices of the Royal Astronomical Society, the research presents a stunning image of a galaxy called NGC 4632 that is 56 million light-years from Earth. Thanks to our VR software, iDaVIE-v, NGC 4632 has been identified as a potential polar ring galaxy, which is one of the most spectacular types of galaxies in the universe, and among the most mysterious.

Paper Press Release: MeerKAT Discovers Mystery Clouds

G. I. G. Józsa, T.H. Jarrett, M.E. Cluver,  et al

Type: Press Release; Paper
An international team led by astronomers Gyula Józsa, Michelle Cluver, and Thomas Jarrett has utilized the South African MeerKAT telescope to discover a mysterious chain of hydrogen gas clouds the size of a massive galaxy. Indeed, the accumulation of so much elemental hydrogen without associated stellar components is the largest yet discovered. Appearing at the edge of a relatively massive group of galaxies, there is the possibility that the cloud chain is gas stripped from group-member galaxies, but it may also be primordial and gravitationally drawn into the group through a cosmic filament pathway. Whatever the case, MeerKAT is proving to be a ground-breaking telescope, and this "dark" cloud discovery should soon be followed by many such discoveries in the exciting days ahead.
Exploring and Interrogating Astrophysical Data in Virtual Reality

T.H. Jarrett, A. Comrie, L. Marchetti, A. Sivitilli, S. Macfarlane, F. Vitello, U. Becciani, A. R. Taylor, T. van der Hulst, P. Serra, N. Katz, and M. E. Cluver

Type: Paper; VR
The arrival of mainstream virtual-reality (VR) headsets and increased GPU power, as well as the availability of versatile development tools for video games, has enabled scientists to deploy such technology to effectively interrogate and interact with complex data. In this paper we present development and results from custom-built interactive VR tools, called the iDaVIE suite, that are informed and driven by research on galaxy evolution, cosmic large-scale structure, galaxy-galaxy interactions, and gas/kinematics of nearby galaxies in survey and targeted observations. In the new era of Big Data ushered in by major facilities such as the SKA and LSST that render past analysis and refinement methods highly constrained, we believe that a paradigm shift to new software, technology and methods that exploit the power of visual perception, will play an increasingly important role in bridging the gap between statistical metrics and new discovery. We have released a beta version of the iDaVIE software system that is free and open to the community.
The WISE Extended Source Catalogue (WXSC)
I: The 100 Largest Galaxies

T.H. Jarrett, M.E. Cluver, M.J.I. Brown, D.A. Dale, C.W. Tsai, and F. Masci

Type: Paper; Data Release
Mid-infrared photometry and measured global properties of the 100 largest galaxies in the sky is presented, including the well-studied Magellanic Clouds, Local Group galaxies M31 and M33, the Fornax and Virgo Galaxy Cluster giants, and many of the most spectacular Messier objects (e.g., M51 and M83). This is the first release of a larger catalog of extended sources as imaged in the mid-infrared, called the WISE Extended Source Catalogue (WXSC).

A MeerKAT view of pre-processing in the Fornax A group

D. Kleiner, P. Serra, F. M. Maccagni, A. Venhola, K. Morokuma-Matsui, R. Peletier, E. Iodice, M. A. Raj,W. J. G. de Blok, A. Comrie, G. I. G. Józsa, P. Kamphuis, A. Loni1, S. I. Loubser, D. Cs. Molnár, M. Ramatsoku, 1, A. Sivitilli, O. Smirnov, K. Thorat, and F. Vitello

Type: Paper; iDaVIE research
We present MeerKAT neutral hydrogen (HI) observations of the Fornax A group, that is likely falling into the Fornax cluster for the first time. Our HI image is sensitive to 1.4 × 1019 atoms cm−2 over 44.1 km s−1, where we detect HI in 10 galaxies and a total of (1.12 ± 0.02) × 109 Msol of HI in the intra-group medium (IGM). We search for signs of pre-processing in the 12 group galaxies with confirmed optical redshifts that reside within the sensitivity limit of our HI image. The central, massive galaxy in our group (NGC 1316) underwent a 10:1 merger ∼ 2 Gyr ago, and ejected 6.6 – 11.2 × 108 Msol of HI that we detect as clouds and streams in the IGM, some forming coherent structures up to ∼ 220 kpc in length. We also detect giant (∼ 100 kpc) ionised hydrogen (Hα) filaments in the IGM, likely from cool gas being removed (and subsequently ionised) from an infalling satellite. The Hα filaments are situated within the hot halo of NGC 1316 and there are localised regions that contain HI. We speculate that the Hα and multi-phase gas is supported by magnetic pressure (possibly assisted by the NGC 1316 AGN), such that the hot gas can condense and form HI that survives in the hot halo for cosmological timescales.
HI Global Scaling Relations in the WISE-WHISP Survey

E. Naluminsa, E. C. Elson, T. H. Jarrett

Type: Paper
We present the global scaling relations between the neutral atomic hydrogen gas, the stellar disk and the star forming disk in a sample of 228 nearby galaxies that are both spatially and spectrally resolved in HI line emission. We have used HI data from the Westerbork survey of HI in Irregular and Spiral galaxies (WHISP) and Mid Infrared (3.4μm, 11.6 μm) data from the Wide-field Infrared Survey Explorer (WISE) survey, combining two datasets that are well-suited to such a study in terms of uniformity, resolution and sensitivity. We utilize a novel method of deriving scaling relations for quantities enclosed within the stellar disk rather than integrating over the HI disk and and the global scaling relations to be tighter when defined for enclosed quantities. We also present new HI intensity maps for the WHISP survey derived using a robust noise rejection technique along with corresponding velocity fields.
iDaVIE-v: immersive Data Visualisation Interactive Explorer for volumetric rendering

Marchetti, Lucia; Jarrett, Thomas H.; Comrie, Angus; Sivitilli, Alexander K.; Vitello, Fabio; Becciani, Ugo; Taylor, A. R.

Type: Paper,
iDaVIE Software Release
We present the beta release of iDaVIE-v, a new Virtual Reality software for data cube exploration. The beta release of iDaVIE-v (immersive Data Visualisation Interactive Explorer for volumetric rendering) is planned for release in early 2021. iDaVIE-v has been developed through the Unity game engine using the SteamVR plugin and is compatible with all commercial headsets. It allows the visualization, exploration and interaction of data for scientific analysis. Originally developed to serve the HI Radio Astronomy community for HI source identification, the software has now completed the alpha testing phase and is already showing capabilities that will serve the broader astronomical community and more. iDaVIE-v has been developed at the IDIA Visualisation Lab (IVL) based at the University of Cape Town in collaboration with the Italian National Institute for Astrophysics (INAF) in Catania.
Galaxy and Mass Assembly (GAMA): A WISE Study of the Activity of Emission-line Systems in G23

Yao, H. F. M.; Jarrett, T. H.; Cluver, M. E.; Marchetti, L.; Taylor, Edward N.; Santos, M. G.; Owers, Matt S.; Lopez-Sanchez, Angel R.; Gordon, Y. A.; Brown, M. J. I.; Brough, S.; Phillipps, S.; Holwerda, B. W.; Hopkins, A. M.; Wang, L.

Type: Paper
We present a detailed study of emission-line systems in the Galaxy And Mass Assembly (GAMA) G23 region, making use of Wide-field Infrared Survey Explorer (WISE) photometry that includes carefully measured resolved sources. After applying several cuts to the initial catalog of ∼41,000 galaxies, we extract a sample of 9809 galaxies. We then compare the spectral diagnostic Baldwin, Philips & Terlevich (BPT) classification of 1154 emission-line galaxies (38% resolved in W1) to their location in the WISE color-color diagram, leading to the creation of a new zone for mid-infrared "warm" galaxies located 2σ; above the star-forming sequence, below the standard WISE active galactic nucleus (AGN) region. Based on our findings, we have created a new diagnostic: [W1 - W2] versus [N II]/[Hα], which has the virtue of separating SF from AGNs and high-excitation sources. It classifies 3 to ∼5 times more galaxies than the classic BPT.
HI study of isolated and paired galaxies: the MIR SFR-M⋆ sequence

Bok, J.; Skelton, R. E.; Cluver, M. E.; Jarrett, T. H.; Jones, M. G.; Verdes-Montenegro, L.

Type: Paper
Using mid-infrared star formation rate and stellar mass indicators in WISE, we construct and contrast the relation between star formation rate and stellar mass for isolated and paired galaxies. Our samples comprise a selection of AMIGA (Analysis of the interstellar Medium in Isolated GAlaxies; isolated galaxies) and pairs of ALFALFA (Arecibo Legacy Fast ALFA) galaxies with HI detections such that we can examine the relationship between HI content (gas fraction, HI deficiency) and galaxy location on the main sequence (MS) in these two contrasting environments. We derive for the first time an HI scaling relation for isolated galaxies using WISE stellar masses, and thereby establish a baseline predictor of HI content that can be used to assess the impact of environment on H I content when compared with samples of galaxies in different environments.
Rising Star: a South African Astronomy Journey

S.A Macfarlane, D. Cunnama, VR Capture

Type: planetarium content, full-length fulldome film
For more details, please contact:
Sally Macfarlane
(24 minutes, VR or Fulldome, 4K or 8K unidirectional) Rising Star takes you on an astronomical journey from our beginnings through the development of astronomy research in South Africa and looks at what the future of astronomy holds for the country. In addition to introducing multi-wavelength and multi-messenger astronomy, it highlights the many remarkable facilities hosted in South Africa along with some of their latest results. The film is accessible to all ages and aims to excite both South African and International audiences about South African astronomy and inspire the next generation of astronomers in the country. As the first of its kind to be produced in Africa, Rising Star hopes to stimulate the production of many more locally produced planetarium films from multidisciplinary fields, with the goal of popularising Africa’s numerous scientific achievements.
The 2MASS redshift survey galaxy group catalogue derived from a graph-theory based friends-of-friends algorithm

Trystan S. Lambert, R. C. Kraan-Korteweg, T. H. Jarrett and L. M. Macri

Type: Paper; Cobra research
A galaxy group catalogue for the recently-completed 2MASS Redshift Survey (2MRS) is presented, consisting of 3022 groups, and 44572 redshifts, including 1041 new measurements for galaxies mostly located within the Zone of Avoidance. The catalogue is generated by using a novel, graph-theory based, modified version of the Friends-of-Friends algorithm. The results and graph-theory methods presented in this paper have been thoroughly interrogated against previous 2MRS group catalogues by making use of cutting-edge visualization techniques and the immersive visualisation facilities of the IDIA Vislab.

The DataToDome Initiative at the Iziko Planetarium in Cape Town and the IDIA Visualisation Lab

Lucia Marchetti, Thomas H. Jarrett1, Angus Comrie, Alexander K. Sivitilli1, Sally Macfarlane, Russ Taylor and MichelleCluver, 2019, ADASS XXI

Type: Paper; Digidome
With the advent of the SKA and other petabyte-scale data facilities, both the data storage and the data interrogation represent two new challenges facing the scientific community. The recently inaugurated Iziko Planetarium 8K Digital Dome and the Inter-University Institute for Data Intensive Astronomy (IDIA) Visualisation Lab are two linked, cutting-edge research facilities in Cape Town that are exploring new approaches to handle the exploration and detailed interrogation of large astronomical (and multi-disciplinary) data sets. These include development of a server-client visualisation tool, the development of Virtual Reality software to explore large 3D data-sets, and the exploitation of the Planetarium 3D immersive projection to visualise big data-sets in the context of the DataToDome initiative.
Virtual Reality and Immersive Collaborative Environments: theNew Frontier for Big Data Visualisation

Alexander K. Sivitilli, Angus Comrie, Lucia Marchetti, and Thomas H. Jarrett 2019, ADASS XXI

Type: Paper; VR
The IDIA Visualisation Laboratory based at the University of Cape Townis exploring the use of virtual reality technology to visualise and analyse astronomicaldata. The iDaVIE software suite currently under development reads from both volumetricdata cubes and sparse multi-dimensional catalogs, rendering them in a room-scaleimmersive environment that allows the user to intuitively view, navigate around andinteract with features in three dimensions.This paper will highlight how the software imports from common astronomy dataformats and processes the information for loading into the Unity game engine. It willalso describe what tools are currently available to the user and the various performanceoptimisations made for seamless use. Applications by astronomers will be reviewed in addition to the features we plan to include in future releases.
Virtual Reality and Immersive Collaborative Environments: the New Frontier for Big Data Visualisation

Alexander K. Sivitilli1 , Angus Comrie, Lucia Marchetti , Thomas H. Jarrett, 2019, ADASS XXI

Type: Poster; VR
iDaVIE immersive Data Visualisation Interactive Explorer:  The aim of the iDaVIE software suite is to render datasets in a virtual room scale 3 D space where users can intuitively view and uniquely interact with their data in ways unafforded by conventional flatscreen and 2 D solutions.

In partnership between UCT Astronomy and IDIA, a laboratory for visual analytics has been created to develop and test hardware and software solutions for interactive visualization of large astronomical data sets. Central to the Visualization Lab is the Iziko Planetarium & Digital Dome, located in the heart of Cape Town. The fulldome facility is optimal for study and investigation of the largest-area data sets, including the Cosmic Web.

The Iziko Digital Dome: June 2018 - Dec 2019

Macfarlane S.A., Jarrett T. , Marchetti L.
January 2020

Type: Report; Digital Dome
Led by UCT Professor Tom Jarrett, with the assistance of post-doctoral fellow Dr Lucia Marchetti and newly appointed 'Planetarium Research Liaison' Dr Sally Macfarlane, IPDD research work has reached increasingly diverse audiences through multiple data demonstrations and researcher interactions. Additionally, it has attracted international interest through pioneering work with the Data2Dome Initiate. New and updated multidisciplinary datasets from the University Research Consortium have been ingested and visualised using the research cluster and Digital Dome theatre, including novel studies into galactic grouping structures and cosmological simulations of the early Universe. The IPDD has also played host to a variety of important events in 2019, including a pivotal meeting of African planetarium partners which successfully launched the African Planetarium Association.
Planned and conceived as both a conventional planetarium — edutainment — and a research facility for visualisation and computing, the Iziko Planetarium 8K Digital Dome upgrade has been an unabridged success in both measures. Since its opening in May of 2017, with operations now reaching the one year stage, the Cape Town public has been dazzled with high-quality production shows, and the Research Consortium, led by the University’s of Cape Town and the Western Cape, has carried out unique and significant research that demonstrates both the power and potential of the facility. This report will highlight the activities of the memorable first year of the Digital Full-dome facility, focusing for the most part on the research side. The authors of this report are the original founders and lead researchers of the new facility.