Australia Telescope National Facility

S&A Colloquium: Michael Busch (NRAO)
2025-11-05 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
OH as a Tracer of “CO-Dark” Gas in the Interstellar Medium Near and Far

Abstract:

Molecular clouds are the birthplace of stars. It is unfortunate then that the most abundant interstellar molecule, molecular hydrogen (H2), is practically invisible in cold molecular clouds (T<100K). Astronomers typically use the second most abundant molecule, carbon monoxide (CO), to trace the bulk distribution of H2 in our galaxy and many others because of its relative brightness and abundance. CO observations alone, however, fail to trace a significant amount of molecular gas, known as “CO-dark” molecular gas. In this talk, I will review the observational evidence for the existence of a significant amount of “CO-dark” gas in the galaxy, then recount the efforts in the 2010s to use OH with the Green Bank Telescope (GBT) to observe the “CO-dark” gas in the Outer galaxy (Busch et al. 2019, 2021). Then I will present recent results on an extremely sensitive pilot survey for 18cm OH emission towards the southern disk of the Andromeda Galaxy, in which trace the large-scale galactic “CO-Dark” molecular gas with the GBT (Busch 2024). A follow-up Andromeda survey is presented. I will discuss recent efforts in combining HCO+ absorption in the diffuse ISM with OH emission to understand the properties of diffuse molecular gas in the ISM and conclude on future work with collaborators in Australia regarding OH as a tracer of “CO-dark” gas.
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Colearnium: Duy Nguyen (CSIRO)
2025-11-06 12:00 - 12:30 (Australia/Sydney) | NSW
A Single-Chip Wideband Digital Receiver for the Australia Telescope Compact Array Upgrade

This week Duy Nguyen will present on “Modernizing Legacy: Wrapping a 25+ Year Computational Fluid Dynamics Codebase“.

Modernizing Legacy: Wrapping a 25+ Year Computational Fluid Dynamics Codebase

Authors: Duy Nguyen, Tisham Dhar, Peter Wang, Jean-Michel Perraud, Klaus Joehnk.Computational Fluid Dynamics (CFD) is the science of using numerical analysis and data structures to solve many processes influencing fluid behavior. CFD requires many complex mathematical representations through various ODE and PDE solvers, and has traditionally been written in Fortran or C++, mostly for their speed in doing massively parallel computations, such as handling array operations and object-oriented features. As such, those codebases have a long-standing legacy in scientific computing, and many established CFD codes are written in them. However, as time goes on, we witness the popularity of a new generation of codebases such as Python, which stems from its simplicity, versatility, and strong community. Extensive libraries and frameworks make Python a popular choice for many developers and scientists alike. It is, however, not a preferred language for core CFD code due to performance limitations and its difficulties with parallelization. This talk explores modernizing a 25+ year-old C++ CFD model, essential for simulating lake conditions, particularly for predicting temperature variations and algal bloom dynamics, by wrapping it with [C-interop] for seamless Python interoperability. Beyond integration, we leverage [Optuna], a powerful hyperparameter optimization framework, to fine-tune models efficiently, transitioning from manual parameter tuning on a laptop to a distributed, scalable workflow powered by Dask Distributed and JupyterHub. This transformation enables automated hyperparameter optimization across many lakes in Australia, helping researchers investigate trends in tuning parameters and derive deeper environmental insights.Attendees will gain insights into:– Wrapping legacy C++ water quality models with CFFI for Python-driven analysis.– Automating and scaling hyperparameter tuning using Optuna across multiple lake ecosystems.– Utilizing Dask Distributed and JupyterHub to accelerate environmental simulations.– Extracting insights from hyperparameter trends to refine large-scale water quality predictions. For researchers, engineers, and data scientists working in environmental modeling, this session provides practical strategies for modernizing legacy systems, scaling model optimization, and enhancing predictive accuracy without sacrificing scientific integrity.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Samuel (On behalf of the co-learnium organisers)

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S&A Colloquium: Dan Rybarczyk (University of Wisconsin-Madison)
2025-11-12 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
New constraints on CO-dark molecular gas properties in the diffuse ISM: Insights from 21cm and 3mm absorption observations

Abstract:

The evolution of the multiphase interstellar medium (ISM) drives galaxy evolution. The transition from diffuse atomic gas to denser molecular clouds sets the initial conditions for star formation, so plays a critical role in this evolution. However, since molecular hydrogen (H2) is invisible in many diffuse environments, observational constraints on the atomic-to-molecular transition remain limited. CO emission is often used to trace H2, but in the diffuse ISM, a significant fraction of H2 is not associated with any CO emission (the “CO-dark” molecular gas). Thankfully, HCO+ absorption at 3mm is an excellent tracer of diffuse molecular gas — with a stable abundance and formation/survival at low column density, HCO+ is a reliable probe of the H2 column density in the diffuse ISM. Here we report observations of HI, HCO+, and CO in absorption toward five diffuse lines of sight. In all of these directions, we detect a kinematically broad, CO-dark signature in HCO+ absorption that is associated with nearly all the cold atomic gas in these directions. We constrain the CO abundances in these directions, which are consistent with chemical model predictions and account for the non-detection of CO. In fact, we show that CO emission or absorption are unlikely to be detected where N(H2) < 7E19 cm^-2, while HCO+ absorption is readily detected for N(H2) > ~fewE18 cm^-2, opening an important window on the HI-to-H2 transition. The diffuse, CO-dark gas associated with broad HCO+ absorption has systematically different properties, including a lower fraction of cold atomic gas and a lower molecular fraction, than CO-bright gas. These observations therefore offer insights on the HI-to-H2 transition that are inaccessible with CO observations. I will briefly discuss future work aimed at uncovering the spatial structure of this diffuse, partially-molecular gas — key to understanding the physics of this critical stage of galaxy evolution.
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S&A Colloquium: Jordan Collier (Australian SKA Regional Centre)
2025-11-18 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Science with the AusSRC: Building on the Precursors Towards the SKA

Abstract:

The Australian SKA Regional Centre (AusSRC) is Australia’s portion of the international SKA Regional Centre Network (SRCNet), which aims to establish and build capability to support the Australian and international SKA science communities, thereby ushering in the next era of astronomical discovery and advanced data processing. This presentation will cover AusSRC’s science support, with highlights from our current SRCNet activities and current round of Australian SKA precursor support, including visibility compression, and the development and implementation of science workflows for representative SKA science, with particular focus on visualisation and analysis capabilities within the Cube Analysis and Rendering Tool for Astronomy (CARTA). A summary will be presented of our future plans, in transitioning toward supporting SKA science verification.
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Colearnium: Sander Voss (CSIRO)
2025-11-20 12:00 - 12:30 (Australia/Sydney) | NSW
MiniXRF: Developing a Lunar X-Ray Fluorescence payload for small platforms

This week Sander Voss will present on “MiniXRF: Developing a Lunar X-Ray Fluorescence payload for small platforms“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Samuel (On behalf of the co-learnium organisers)

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Apply for the 2026APR semester
2025-11-21 08:00 - 2025-12-16 17:00 (Australia/Sydney) | NSW
Overview

We’re pleased to announce that proposals for ATNF observing time are now open for the 2026APR semester. Grab your chance to use some of our new receivers and facilities.

Apply now for:

Our ASKAP radio telescope (including CRACO)

Our Australia Telescope Compact Array

Murriyang, our 64-m Parkes radio telescope

The Tidbinbilla radio antennas: the 70-m antenna Ballima (DSS-43) , and the 34-m (DSS-34) antenna;

The Long Baseline Array

Mark your calendars: the deadline for all proposals is 06:00 UT (17:00 Sydney local time) on Tuesday, 16 December 2025.

To submit your proposal, visit our online proposal application system, OPAL.
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S&A Colloquium: Anna Ivleva (Observatory of Munich / Ludwig Maximilian University)
2025-11-21 11:00 - 12:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Odd Radio Circles (ORCs): probing radio features at group scales with simulations

Abstract:

Extragalactic radio astronomy has proven to be immensely useful in the study of high energy particle physics by constraining the acceleration of cosmic ray electrons and their subsequent synchrotron emission. Investigations of galaxy clusters have shown to be particularly fruitful, since such massive environments grant favourable conditions for efficient particle acceleration via merger driven shocks. Yet, a new class of radio objects discovered only a few years ago imposes the question if also merger shocks in less massive systems can accelerate CR electrons to GeV energies. Specifically, a growing number of observations is pointing towards the existence of ringlike features around small galaxy groups and even Milky Way-like objects, accordingly titled Odd Radio Circles (ORCs). Recent works have proposed that these could be interpreted as radio analogs to the merger shocks observed in more massive systems. However, ORCs are appearing in a colder and less magnetized medium than the radio features in galaxy clusters, challenging particle acceleration mechanisms in more constraining environments. Now, by interpreting multiple observed ORCs at different stages as an evolutional time sequence and comparing them to simulations of such systems, one can infer underlying properties of these unique features, while simultaneously testing the limits of diffusive shock acceleration (DSA). To this end, I will present the first of its kind magnetohydrodynamical simulation of a galaxy group, utilising on-the-fly treatment of spectral cosmic rays. I will study the emerging radio features and discuss both similarities and differences to the observed counterparts. Finally, I will review the relative importance of DSA in the formation of ORCs compared to galactic sources of high energy particles, such as supernovae and AGN.
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S&A Colloquium: Jennifer West (Dominion Radio Astrophysical Observatory)
2025-11-26 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Is the heliopause seen in radio synchrotron emission?

Abstract:

Diffuse radio synchrotron emission originating in the Milky Way fills the entire sky, even at high Galactic latitudes. The emission is highly linearly polarised, and comes from high energy CRs moving in the Galaxy’s magnetic field. Planck has measured the orientation of this emission and has mapped the magnetic field pattern across the sky, however, we do not know if the origin of the pattern is distant (tracing the large-scale magnetic field) or nearby (tracing the Local Bubble, a massive superbubble where our Sun now resides). The reality is the emission must originate at a wide range of distances. In this talk, I will present evidence that some of this emission has its origin in the interaction between the heliopause and the very local interstellar magnetic field. The emission is polarised, and traces the local interstellar magnetic field as it wraps around the heliosphere at the heliopause boundary, which is related to the Sun’s motion through space, and which has previously been revealed through a bright ribbon of emission detected by NASA’s Interstellar Boundary Explorer (IBEX).

Please note that the event timezone is AEDT (UTC+11 hrs)

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Colearnium: Adriana Parra Ruiz (CSIRO)
2025-11-27 12:00 - 12:30 (Australia/Sydney) | NSW
‘Artificial Intelligence in 2030 and beyond’: lessons from the Science and Technology in Society forum

This week Adriana Parra Ruiz will present on “‘Artificial Intelligence in 2030 and beyond’: lessons from the Science and Technology in Society forum“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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S&A Colloquium: Sam Taziaux (Ruhr University Bochum)
2025-12-03 12:00 - 13:00 (Australia/Sydney) | 26 Dick Perry Ave, Kensington WA 6151, 26 Dick Perry Avenue, Kensington, Washington, 6151
MEDUSA — Magnetic-field Evolution in Dwarf galaxies from Ultra-deep SKA Analysis

Abstract:

Dwarf galaxies are an important class of galaxies, which are known to serve as proxy for the early Universe and play a crucial role in the formation and evolution of larger galaxies. To understand the underlying emission mechanism and the physics that drive the radiation far away from their origin, we perform radio continuum polarimetry studies using deep MeerKAT observations. With the MEDUSA (Magnetic field Evolution in Dwarf galaxies Using SKA Analysis) project, we present to-date the largest radio polarimetry study of dwarf galaxies, including HI kinematics. Analysis of the spectrum reveals potential energy losses with rapid dissipation of electrons over kiloparsec scales, a phenomenon contrasting sharply with observations from grand spiral galaxies. Furthermore, small-scale dynamos in the star-fomation knots and a correlation between the level of depolarisation and the star formation histories deepen the understanding of this low mass systems. These findings provide evidence of intense material feedback into the intergalactic medium, a process expected to be prevalent in the protogalaxies of the early Universe.

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Colearnium: Phil Collins (CSIRO)
2025-12-04 12:00 - 12:30 (Australia/Sydney) | NSW
Contractor HSE Management – Procedure awareness

This week Phil Collins will present on “Contractor HSE Management – Procedure awareness“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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Colearnium: Minh Huynh (CSIRO)
2025-12-11 12:00 - 12:30 (Australia/Sydney) | NSW
Complex Projects: The Vasa, and how not to build a ship

This week Minh Huynh will present on “Complex Projects: The Vasa, and how not to build a ship“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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Colearnium: LJ Spriggs (CSIRO)
2025-12-18 12:00 - 12:30 (Australia/Sydney) | NSW
Galactic Archaeology through Chemical Cartography

This week LJ Spriggs will present on “Galactic Archaeology through Chemical Cartography“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

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Stefan Duchesne

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Colearnium: Jack Steele (CSIRO)
2026-01-22 12:00 - 12:30 (Australia/Sydney) | NSW
How CSIRO engages with government

This week Jack Steele will present on “How CSIRO engages with government“.

What are ‘Estimates’ and what is CSIRO’s role? How do we deal with ‘our’ Minister? What’s the latest on the Strategic Examination of R&D and the CSIRO parliamentary inquiry? What does it mean to say that CSIRO is part of government, and how does that affect our engagement with them?

At this co-learnium hear from one of CSIRO’s government experts, Jack Steele, on how and why CSIRO works with government and Ministers across a range of issues. There will be plenty of useful tips and time for questions.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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S&A Colloquium: Ashna Gulati (University of Sydney)
2026-01-28 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
From Jets to Mergers: Multiwavelength Signatures of Synchrotron Transients

Abstract:

Synchrotron transients arise from some of the most energetic explosions in the Universe and trace the interaction of relativistic or sub-relativistic outflows with their surrounding environments. These interactions generate shocks that accelerate particles and amplify magnetic fields, producing broadband synchrotron emission. While the underlying emission mechanism is broadly similar across sources, differences in progenitor systems give rise to a wide range of outflow velocities, energies, and light-curve behaviours. Broadband observations are therefore a powerful tool for probing the physics of these extreme events, from compact object interactions to stellar explosions.

In this talk, I present results from three complementary approaches to studying synchrotron transients: targeted wide-field radio surveys, untargeted extreme transient searches, and rapid response follow-up. I discuss late-time ASKAP searches for radio afterglows from compact object mergers detected by LIGO–Virgo, the discovery and detailed characterisation of the luminous and long-lived extragalactic radio transient ASKAP J0055–2558, and a comprehensive radio-to-X-ray study of the exceptionally bright GRB 240825A. Together, these studies demonstrate how broadband observations enable robust constraints on relativistic outflows and establish radio surveys and electromagnetic follow-up as a critical tool for exploring the extreme transient Universe in the SKA era.

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Colearnium: Carmen Martinez Harris & Michael Cowley (QUT)
2026-01-29 12:00 - 12:30 (Australia/Sydney) | NSW
A Framework for Preserving Indigenous Astronomy in SEQ

This week Carmen Martinez Harris & Michael Cowley will present on “A Framework for Preserving Indigenous Astronomy in SEQ“.

Please let me know if you’re willing to present at a future Co-learnium or have requests for specific talks, thanks!

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Stefan Duchesne

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S&A Colloquium: Kovi Rose (University of Sydney)
2026-02-04 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Probing the Timescales of Radio Variability: From Late-time Supernovae Re-Brightening to Long Period Transients

Abstract:

We have entered the age of big data in astrophysics and radio astronomy is no exception. Wide-field surveys with the Australian SKA Pathfinder (ASKAP) radio telescope are finding millions of radio-bright sources in the southern skies. In this talk I will speak about three recent discoveries and their implications on our understanding of stellar magnetism in fully convective stars, binary evolution in accreting systems, and the mass-loss history of supernova progenitors. The first comes from our detection of periodic bursts from an ultracool brown dwarf, the latest spectral type star ever found to produce radio emission. Second, we have found orbitally-modulated X-ray and radio pulses from a newly discovered long period transient. And finally, we are finding supernovae re-brightening years after their optical discovery, as the blast wave interacts with shells of circumstellar material. Finding and studying these rare transients is helping us explore astrophysical environments that cannot be studied on Earth.

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S&A Vacation Student Symposium
2026-02-05 00:00 - 23:59 (Australia/Sydney) | NSW
One day symposium where undergraduate students will give a short talk on the project they have worked on over the summer

The symposium will be held in person at two locations and also online, commencing with an introductionfrom S&A Director, Dr Douglas Bock.Marsfield Lecture Theatre, NSW at 11:30 am AEDTKensington Auditorium, WA at 8:30 am AWSTLink to the program

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Colearnium: Tisham Dhar (CSIRO)
2026-02-12 12:00 - 12:30 (Australia/Sydney) | NSW
Earth Observation and Helio physics foundation models

This week Tisham Dhar will present on “Earth Observation and Helio physics foundation models“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

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Stefan Duchesne

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ATNF Futures 2030 Workshop
2026-02-18 10:00 - 2026-02-19 17:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Overview

This workshop invites the Australian community to present science and technology ideas for the post-2030 era that deliver transformational advances with existing or upgraded facilities and new demonstrators in the SKA era.

Inyarrimanha Ilgari Bundara, our Murchison Radio-astronomy Observatory is one of the best sites for radio astronomy observations in the world, and the ATNF should take advantage of its unique environment. With SKA-Mid and SKA-Low telescopes coming online towards the end of the decade for science verification and full operations, and DSA-2000 operating from the late 2020s, it is timely for the community to start planning for post-2030 science and technology pathways.

The ASKAP telescope was built to:

Help establish an observatory site for the SKA Observatory’s SKA-Low telescope, and

Demonstrate SKA survey science technologies.

Following the construction of ASKAP, CSIRO ran an open proposal process, and initiated the 5-year Science Survey Projects, which are still in progress.

The first two aims have been achieved, and the surveys are planned to be completed by the end of the decade.

We have supplied a document outlining a set of broad facility and technology concepts, and the boundary conditions for the discussion. An ASKAP upgrade path is one of the concepts provided for discussion:
Concept documentPDF450 KB
We will then invite abstracts for presentations that take one or more of these concepts and present a scientific and/or technology vision. These can be submitted via the registration form.

Aims of the Workshop

To canvas ideas on the unique and world-leading science that ATNF can do in the 2030s

To bring the Australian community into the conversation about the future of mid-high frequency radio astronomy

To generate new ideas and collaborations within Australia and internationally.

Location

In-person at Marsfield and online

Registration

Abstract submission has closed. Any abstracts proposed through the form will not be considered. Registration for in-person attendance has now closed. Online registration remains open.

Online registration
Online details will be provided closer to the date.

Organiser

Organising Committee:

Cathryn Trott

George Hobbs

Kelly Gourdji

Josh Preston Pritchard

Aidan Hotan

Nithya Thyagarajan

Keith Bannister

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S&A Colloquium: Joe Grundy (Curtin University)
2026-02-25 12:00 - 13:00 (Australia/Sydney) | CSIRO – Kensington, Australian Resources Research Centre (ARRC), 26 Dick Perry Ave, Kensington, WA, 6101, Australia
Investigating the Complex Radio Spectra and Infrared-Radio Correlation in Nearby Starforming Galaxies

Abstract:

In my recently accepted thesis, I examined the radio continuum emission of galaxies to determine how the physical processes that occur within galaxies modify the radio spectral energy distribution and physical distribution of radio emission. I studied the resolved radio continuum emission of 27 nearby star forming galaxies with facilities including MWA, ASKAP, ATCA and ALMA to examine the impact of cosmic ray electron energy loss and radio continuum absorption mechanisms as well as cosmic ray transport on the radio spectral energy distribution and their relations to a galaxies physical properties. I have also examined the relationships between radio continuum emission and star formation through the infrared to radio correlation and how these relationships are affected by physical processes within galaxies. Overall I find that the radio continuum emission of star forming galaxies is much more complex than simple two component synchrotron and free-free power law emission with factors such as ionisation losses, synchrotron losses and free-free absorption impacting the radio emission differently in each galaxy depending on a galaxies size, star formation rate and gas properties. A thorough understanding of the links between the physical properties of a galaxy and its radio spectral energy distribution is vital to be able to better calibrate radio star formation rate measures in preparation for future broad-band, all-sky radio surveys with telescopes like the SKA.

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Colearnium: Andrew Bolin (CSIRO)
2026-02-26 12:00 - 12:30 (Australia/Sydney) | NSW
A peek inside Port Kembla Steelworks

This week Andrew Bolin will provide “A peek inside Port Kembla Steelworks“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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Colearnium: Phil Edwards (CSIRO)
2026-03-05 12:00 - 12:30 (Australia/Sydney) | NSW
What was the ATCA built for (and what has it actually done)?

This week Phil Edwards will tell us “What was the ATCA built for (and what has it actually done)?“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

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Stefan Duchesne

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S&A Colloquium: Eric Burt (NASA/JPL, 2025 IEEE Distinguished Lecturer on Frequency Control)
2026-03-12 12:00 - 13:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
Frequency Standard Contributions to Limitations on the Signal-to-Noise Ratio of Very Long Baseline Interferometry Observations

Abstract:

Since its observation in 2019, the first image of a super-massive black hole using Very Long Baseline Interferometry (VLBI) between a network of Earth-based radio telescopes has generated much scientific and public interest, including the possible extension to include one or more space-based radio antennas in order to obtain higher image resolution. The VLBI technique assumes that each radio telescope has its own frequency standard or “clock,” and a key requirement for that frequency standard is that it have sufficient stability and precision to enable the phase-coherent combination of signals from the independent radio telescopes. For ground-based radio telescopes, the state-of-practice is to have a hydrogen maser co-located. The number of frequency standards that are both space-qualified and perform well enough for this type of VLBI is a small subset of those available on the ground. Among these, it will be necessary to determine what type of frequency standard performance is really required. In addition, given the high cost of launching instruments into space, it may be necessary to make difficult trade-offs between instrument size, and performance. To facilitate this trade space, we derive a metric that directly links frequency standard noise characteristics to the signal-to-noise (S/N) ratio as a function of averaging time for the central VLBI observable, known as the “visibility.” Using this metric, we find that among the existing space clock candidates, only an Ultra-Stable Oscillator (USO) and space hydrogen maser are potentially viable. Furthermore, a USO will only be effective for relatively short integration times for the high observational frequencies required, which are typically of order 100 GHz or higher. While a hydrogen maser can extend the averaging time, it is likely to have prohibitive size and cost for a space VLBI node. We also investigate emerging frequency standards, including optical clocks, and find that the best option may be the optical local oscillator used in an optical clock by itself without the atomic reference. This approach can greatly reduce size and complexity of the frequency standard by eliminating the atomic reference while providing a limit on VLBI visibility S/N significantly higher than what is possible with a hydrogen maser.

Please note that the event timezone is AEDT (UTC+11 hrs), and it will be held at Payne Scott room instead of the lecture theatre.
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ATUC Open Day
2026-03-19 09:00 - 17:00 (Australia/Perth) | Kensington Auditorium, 26 Dick Perry Avenue, Kensington, Western Australia, 6151, Australia
Overview

The ATUC Open Day on 19 March 2026 will be held in the Auditorium at Kensington. Remote attendance will be made available via Teams. All are welcome to attend.

If you, as a user (or potential user) of the ATNF, are aware of any issues that need to be raised at the next ATUC meeting, or would like to offer feedback on ATNF activities and facilities, you can do so via the ATUC Community Submission Form or by contacting any member of ATUC.

To participate in the ATUC Open Session, please register in advance using the button below. The registration deadline is 17:00 AWST on 5 March 2026.
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S&A Colloquium: Luca Ighina (Harvard Center for Astrophysics)
2026-03-25 12:00 - 13:00 (Australia/Sydney) | CSIRO – Kensington, Australian Resources Research Centre (ARRC), 26 Dick Perry Ave, Kensington, WA, 6101, Australia
A New Radio Window on the Growth of the First Supermassive Black Holes

Abstract:

From reionizing the Universe to quenching star formation in massive galaxies, accreting supermassive black holes (SMBHs), or active galactic nuclei (AGN), are thought to play a pivotal role in early galaxy evolution. Growing observational evidence, including recent results from JWST, suggests that accreting black holes are both more abundant and more massive at than predicted by current theoretical models. In this talk I will present recent observational results on accreting black holes in the early Universe, with a particular focus on radio-powerful AGN. I will show how relativistic jets can play an important role in both the rapid assembly of very massive black holes and the regulation of star formation in their host galaxies in the early Universe.

While exciting, current studies focus on optically luminous AGN, which likely represent only the tip of the iceberg of the SMBH population at early cosmic times. Heavily obscured AGN, whose accretion signatures are hidden at optical and near-infrared wavelengths, are predicted to dominate the high-z AGN population, yet these sources remain largely unconstrained from an observational point of view. The synergy between next-generation radio and near-infrared wide-area surveys will soon open a new window on this elusive population. In particular, radio observations can reveal the presence of relativistic jets, and therefore ongoing black hole accretion, even in systems that are obscured at optical wavelengths. The combination of ASKAP/EMU and EUCLID-wide surveys will provide the deepest multi-wavelength view of the extra-Galactic southern sky, enabling the construction of the first large, unbiased census of accreting black holes at z>6. As an example of the power of this synergy, I will present a preliminary cross-match of EMU and Euclid over the EUCLID deep field South (∼25 deg2).

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S&A Colloquium: Matt Miles (Vanderbilt University)
2026-03-26 12:00 - 13:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
All Models Are Wrong: Noise Modelling in Pulsar Timing

Abstract:

Pulsar timing arrays are only as good as the timing residuals they produce — and those residuals are only as clean as the method used to extract them. Traditional template-matching approaches measure pulse time-of-arrival (TOA) by fitting a single fixed or radio-frequency dependent template to observed profiles, but this leaves a critical vulnerability: any stochastic variation in pulse shape is silently absorbed into the TOA as a systematic bias, quietly corrupting the signals we are trying to extract.

SCULPT is a new technique built of old ideas that fixes this at its source. By constructing a basis directly from observed profiles via SVD, SCULPT learns the true structure of pulse shape variability from the data itself — no analytic assumptions, no oracle knowledge required. Stochastic shape changes are absorbed into nuisance amplitude coefficients within this basis, keeping them out of the timing solution. The result is a variational profile basis that is optimally adapted to the actual pulse morphology: expressive where it needs to be, simple everywhere else.

I will present the methodology behind this process and explore with the audience what it is we’re trying to achieve and why it’s an important goal.

Please note that the event timezone is AEDT (UTC+11 hrs) and will be held in the Faraday room
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S&A Colloquium: Valentina Di Marco (University of Melbourne)
2026-03-31 15:00 - 16:00 (Australia/Sydney) | Marsfield Lecture Theatre, 26 Pembroke Road, Marsfield, NSW, 2122, Australia
All Models Are Wrong: Noise Modelling in Pulsar Timing

Abstract:

Pulsar timing arrays, like any experiment, depend on accurate noise modelling to detect nanohertz gravitational waves. But the noise itself is much more complex than in some other experiments. It is multi-component and, due to the astrophysical origin of several noise processes, often uncertain and difficult to model accurately. In this talk, I explore what happens when our noise models are wrong.

I show that misspecified noise can bias gravitational-wave inference and distort spectral estimates. While these effects are sometimes conservative, they can also lead to systematically incorrect conclusions, highlighting the need to account for model uncertainty properly.

I then present a transdimensional Bayesian approach for noise analysis that lets the data decide which noise processes are present in the signal. By jointly performing model selection and parameter estimation, this framework provides a more robust and statistically consistent way to analyse pulsar timing data.

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S&A Colloquium: Yuxiang Qin (Australian National University)
2026-04-01 12:00 - 13:00 (Australia/Perth) | CSIRO – Kensington, Australian Resources Research Centre (ARRC), 26 Dick Perry Ave, Kensington, WA, 6101, Australia
Inferring properties of the first galaxies and intergalactic medium with 21-cm cosmology

Abstract:

The redshifted 21-cm signal provides a unique probe of the first galaxies and their imprint on the thermal and ionization state of the intergalactic medium (IGM) during the Cosmic Dawn and Epoch of Reionization. In this talk, I present a unified inference framework that jointly interprets constraints from low-frequency interferometers (e.g., HERA and MWA) and global-signal experiments such as EDGES, in combination with complementary galaxy and CMB observations.

By jointly modelling these datasets, we find converging evidence that the IGM was heated early, ruling out a broad class of cold reionization scenarios and placing new constraints on the X-ray emissivity of the first galaxies. Within a galaxy-driven framework, these results imply enhanced high-redshift X-ray production relative to local scaling relations, potentially driven by metal-poor stellar populations and their remnants. In parallel, global-signal analyses provide independent constraints on the timing and amplitude of the cosmic dawn signal, and serve as a critical test of its astrophysical interpretation.

As these early sources are likely beyond the reach of direct detection, even for facilities such as JWST, the 21-cm signal remains a uniquely powerful probe of their collective impact. Looking ahead, I will show how the Square Kilometre Array (SKA) will transform this field, enabling precision constraints on the thermal history of the IGM and the properties of the first galaxies.

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Colearnium: Mark Wieringa (CSIRO)
2026-04-02 12:00 - 12:30 (Australia/Sydney) | NSW
“Overview of my time at ATNF: 35 years in 25 minutes”

This week Mark Wieringa will provide an “Overview of my time at ATNF: 35 years in 25 minutes“.

Please let me know if you’re willing to present at a future co-learnium or have requests for specific talks, thanks!

Kind regards,

Stefan Duchesne

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