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How do cluster environments affect the molecular gas in galaxies?

Speaker: Dr Nikki Zabel
Affiliation: Kapteyn Astronomical Institute, University of Groningen
Date: 24 February 2022, 1200 SAST
Venue: Virtual, join through this Zoom link or YouTube link

Understanding galaxy formation and evolution is one of the key goals of astronomical research. With roughly half of the galaxies in the local Universe residing in dense environments, it is therefore important to study the effects of environment on galaxy evolution. It has been known for several decades that galaxy clusters harbour a relatively large fraction of early-type galaxies. This suggests that dense environments can cause the premature quenching of star formation. Several environmental processes have been suggested to contribute to this, such as ram pressure stripping, starvation, violent fly-bys, and tidal interactions. However, the relative importance of these mechanisms, and how exactly they lead to the quenching of star formation, is still poorly understood.

Typically distributed in an extended disc, atomic gas has long served as an excellent tracer for environmental processes. However, it is the molecular gas that is the direct fuel for star formation. Therefore, any direct effects of the cluster environment on the more tightly bound and centrally located molecular gas would have strong implications for galaxy evolution in dense environments.

In this talk Dr Zabel will discuss studies of the molecular gas in galaxies in the nearby Fornax cluster, and will close with some early results from the recently published paper “VERTICO: The Virgo Environment Traced in CO Survey”

SRG Orbital Observatory: Map of the entire Sky in X-Rays and its variability over time

Speaker: Prof Rashid Sunyaev
Affiliation: Space Research Institute, Moscow & Max-Planck Institute for Astrophysics, Garching
Date: 20 January 2022, 1200 SAST

SRG X-ray Orbital Observatory was launched to the second Lagrange point of the Sun-Earth system (1.5 million km from the Earth) on July 13th, 2019. It constructed four full maps of the sky and detected in X-rays more than 2 million quasars, 50 thousand clusters of galaxies, half a million stars with hot coronae, supernovae remnants, accreting neutron stars, and stellar mass black holes in our Galaxy.

Many X-ray sources demonstrate strong variability. For example, we have already detected more than 60 TDEs (Events of the Tidal Disruption of the stars in the vicinity of supermassive black holes in the centres of distant galaxies).

Technology, policy and politics: critical success factors in high-technology infrastructure projects

Speaker: Dr Rob Adam
Affiliation: SARAO
Date: 18 November 2021, 1200 SAST

The article examines critical success factors in high technology projects by comparing the Square Kilometre Array, the Pebble Bed Modular Reactor and the Reactor Conversion Project in the context of a historical view of South African technology policy. These three complex endeavours illustrate rather well what mistakes can be made in the conceptualising and in the execution of such projects. The article argues that the confluence of a range of diverse factors such as sufficient prototyping, understanding and balancing political stakeholders, getting the organisational culture right and managing ambitions and aspirations are necessary for success to be achieved.

Interferometric SETI searches with the Breakthrough Listen initiative

Speaker: Dr Cherry Ng
Affiliation: Dunlap Institute, SETI Institute & Berkeley SETI Research Center
Date: 29 September 2021, 1600 SAST

The search for technosignatures - remotely observable indicators of advanced extraterrestrial life - addresses one of the most profound questions in science: are we alone in the universe as intelligent life? The Breakthrough Listen program is leading the most concerted search for extraterrestrial intelligence (SETI) effort to-date through radio and optical surveys of nearby stars, nearby galaxies and the Milky Way galactic plane, thus representing the best chance the human race has ever had to detect a technosignature. Recently, Breakthrough Listen has partnered with the SETI Institute to develop commensal SETI search capabilities on some of the most sensitive radio inteferometers, including the Allen Telescope Array (ATA), the Very Large Array (VLA) and MeerKAT. Interferometric radio telescopes have the advantage of providing a larger field of view, maximizing the SETI survey speed. In this talk, we will present the latest updates on these surveys and conclude with a refreshed outlook on SETI search using next generation telescope facilities.

The Shapley Supercluster as seen by ASKAP and MeerKAT

Speaker: Dr. Tiziana Venturi
Affiliation: IRA/INAF, Bologna
Date: 26 August 2021, 1600 SAST

The Shapley Supercluster is the largest gravitationally bound supercluster in the nearby Universe, where cluster mergers and group accretion are taking place at the present epoch. Given the broad mass range of the clusters and groups in this region of the sky, this is an ideal place to study the signatures of minor mergers in the radio band, which have been so far unaccessible due to the limitations of the past generation of radio interferometers. In this talk new results on the central region of the Shapley Supercluster as revealed by ASKAP and MeerKAT are shown. The observations show that even minor mergers are spectacular, and can give rise to Mpc scale diffuse radio emission in galaxy clusters, as well as radio features which bear invaluable information on the formation of large scale structures in the Universe.

Radio Galaxies and the SKA: Seize the day and apologise later | Part 2

Speaker: Dr. Bernie Fanaroff
Affiliation: SARAO
Date: 29 July 2021, 1600 SAST

Dr. Bernard “Bernie” Fanaroff takes us on a retrospective journey of his collaborative work on the classification of radio galaxies, and his account of the history of the SKA, South Africa and the becoming of the MeerKAT telescope in South Africa.

Radio Galaxies and the SKA: a little bit of history about both | Part 1

Speaker: Dr. Bernie Fanaroff
Affiliation: SARAO
Date: 22 July 2021, 1600 SAST

Dr. Bernard “Bernie” Fanaroff takes us on a retrospective journey of his collaborative work on the classification of radio galaxies, and his account of the history of the SKA, South Africa and the becoming of the MeerKAT telescope in South Africa.

Algorithms for interferometric radio processing: towards 100k x 100k images

Speaker: Dr André Offringa
Affiliation: ASTRON
Date: 3 June 2021, 1600 SAST

Current and future radio telescopes like LOFAR, MeerKAT and the SKA produce extremely large data sets. Making scientific products from these large data sets is challenging but of high importance, and allow us to analyze our Universe more distant, at earlier times and with more detail than ever. Ideally, observatories make products available that are (science-) ready for astronomers to look at, but this requires efficient and automated algorithms that process the data in scientifically credible ways. In my talk I will focus on this kind of processing algorithms, and describe a few novel algorithms that I have work on, including AOFlagger, WSClean and DP3-DDECal. Together, these allow us now to make 100,000 by 100,000 pixel images with LOFAR, and prepare use for LOFAR2 and the SKA.

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Rhodes Centre for Radio Astronomy Techniques and Technologies