Australia Telescope National Facility

Colearnium: Ivy Wong (CSIRO)
2024-11-14 12:00 - 12:30 (Australia/Sydney)
Ivy’s Trip to NRAO

This week Ivy Wong will present on “Ivy’s Trip to NRAO”.

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: Meriem Behiri (SISSA)
2024-11-13 15:00 - 16:00
SHORES: Serendipitous H-ATLAS-fields Observations of Radio Extragalactic Sources with the ATCA

Abstract

In this presentation, we explore the advantages of integrating data from the radio to the far-infrared (FIR) spectrum for characterizing dusty star-forming galaxies (DS-FGs). These galaxies are believed to be the star-forming progenitors of local massive quiescent galaxies and are pivotal in reconstructing the cosmic star formation rate density up to high redshifts (Talia+21,Enia+22,Behiri+23). Due to their heavily obscured nature by dust, DSFGs are often invisible in near-infrared/optical/UV bands, necessitating observations at longer wavelengths, primarily in the FIR band where dust emission occurs, and in the radio band, unaffected by dust absorption. By combining data from these spectral regions, even the most dust-obscured objects can be characterized, providing insights into their age, dust temperature, and star-formation activity, and enabling differentiation between various galaxy populations evolving throughout cosmic history (Behiri+24). In this context, we introduce the Serendipitous H-ATLAS fields Observations of Radio Extragalactic Sources (SHORES) survey. SHORES is a newly conducted survey at 2.1 GHz performed with the Australia Telescope Compact Array, comprising 27 shallow fields and 2 deep fields centered around a candidate lensed galaxy. These fields are complemented by Herschel observations (H-ATLAS sgp) and data from various surveys (KIDS, VIKING, Euclid, DES, eRosita..), as well as SKAO pathfinders surveys (e.g., RACS). The extensive 200+ hours of observations with the ATCA interferometer have enabled us to achieve a 33 uJy rms for the shallow fields and 5 uJy rms for the deep fields, resulting in a collection of more than 3200 sources. To fully characterize the radio spectra, the SHORES deep field is observed at 5.5, 9, and 20 GHz, providing crucial insights into various radio populations, including Active Galactic Nuclei (AGN) and Star-Forming Galaxies (SFGs) (Behiri+, in prep.). Additionally, all SHORES observations incorporate polarization measurements, offering a unique opportunity to explore the polarization nature across a substantial sample of AGN and SFGs (Galluzzi+, in prep.). This comprehensive, panchromatic approach provides a crucial perspective for unraveling the mysteries of the radio sky. The broad multi-wavelength coverage of the SHORES survey positions it as an ideal candidate for studying the diverse array of objects in the radio zoo, thereby preparing us for forthcoming SKAO observations.
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Colearnium: Emily Kerrison (USyd)
2024-11-07 12:00 - 12:30
2,000 years of twinkling: lessons learned from a brief history of astronomical scintillation

This week Emily Kerrison will present on “2,000 years of twinkling: lessons learned from a brief history of astronomical scintillation”.

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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Colearnium: Georgia Stewart (UTas)
2024-10-31 12:00 - 12:30
An (AGN) Ghost Story

This week Georgia Stewart will present on “An (AGN) Ghost Story”.

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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Colearnium: Phil Edwards (CSIRO)
2024-10-24 12:00 - 12:30
Parkrun? But I don’t run!

This week Phil Edwards will present on “Parkrun? But I don’t run!”.

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: Simon Weng (University of Sydney)
2024-10-23 15:00 - 16:00
The Distribution of Cool Gas In and Around Galaxies

Abstract

Unraveling the evolutionary paths of galaxies remains a key focus in astronomy. Over the past decade, the circumgalactic medium (CGM) has been recognised as a pivotal component in this research, serving as a record keeper of the processes of accretion and outflows, which move gas to and from the interstellar medium. In this talk, I will explore the CGM properties of galaxies, linking these properties to their stellar properties and using simulations to guide the interpretation of the observational findings.
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Colearnium: Jordan Collier (CSIRO)
2024-10-17 12:00 - 12:30
CARTA – Cube Analysis and Rendering Tool for Astronomy

This week Jordan Collier will present on “CARTA – Cube Analysis and Rendering Tool for Astronomy”.

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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Samuel (On behalf of the co-learnium organisers)

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De Laeter Colloquium: Ron Ekers (CSIRO)
2024-10-10 15:00 - 16:00
Exploring the nature of scientific discoveries with examples from radio astronomy

Abstract

I will discuss the nature of scientific discoveries which are a key driver for the advancement of science. In the 90-year history of radio astronomy many of the most significant advances in our understanding of the Universe have resulted from technology enabled serendipity. I will discuss a few of these cases (quasars, pulsars and the galactic centre) in detail to illustrate how the path to discovery can be very different from the widely accepted scientific methodology. I will also comment on how the vision to explore the unknown has influenced the development of the SKA and its precursors. (Image credit: Daily Telegraph)

The de Laeter Colloquium series features distinguished national and international scientists as speakers, aimed at enhancing interaction between CSIRO, SKAO, the two ICRAR nodes, and high-profile centres of astronomical research around the world.
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S&A Colloquium: Manasvee Saraf (UWA)
2024-10-09 15:00 - 16:00
Constraining neutral hydrogen and its environment using radio interferometry

Abstract

In this talk, I will present an overview of my PhD research, conducted over the past three and a half years as a CSIRO co-supervised student. My thesis investigates the relationship between neutral atomic hydrogen gas (HI) and its environment using radio interferometric observations. I will highlight my discovery of HI absorption in the brightest cluster galaxy (BCG) of the Norma cluster, based on ATCA data, which supports the BCG’s recent arrival into the cluster core. Additionally, I will discuss my detection of 25 HI emission detections towards Norma using ASKAP data, alongside my contribution to and findings from the optimisation of the WALLABY data-processing and HI source-finding pipelines in the presence of bright continuum sources. Finally, I will contextualise my findings within a broader range of environments, focusing on my analysis of the scatter in the HI-halo mass relation of central galaxies from the xGASS survey, where I found a strong correlation with stellar specific angular momentum, offering key insights for simulations.
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Colloquium: Rhea–Silvia Remus and Lucas Kimmig (LMU Munich)
2024-10-02 14:00 - 15:00 | Kensington Lecture Theatre, WA, Australia
From Cosmic Dawn to Present-Day: Galaxy Formation and Evolution from Simulations

Abstract:

Observations of galaxies have revealed a puzzle of different properties seen from redshifts of z=10 or higher to present-day, using multi-wavebands and integral field spectroscopy to probe the stellar light, the gas, but also infer the dark matter content of galaxies at different epochs of time. However, as observations represent snapshots in time, connecting the puzzle pieces in their evolution requires simulations to bridge our understanding of galaxy formation at early and late times. We will present the results of this endeavour using one of the largest sets of fully hydrodynamical cosmological simulations, the Magneticum Pathfinder simulation suite and its adjacent simulations, going from the earliest formation of galaxies to their present-day counterparts. We will highlight how metals in the stars reveal a galaxy’s assembly history, show that most present day main sequence galaxies have experienced episodes of quiescence and rejuvenation, and demonstrate how kinematics and low surface brightness features are connected. We invite you to join us on this journey of galaxy formation through cosmic time, and discover how simulations and observations together shed light on how structures have formed in our Universe.
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Meet monazite, a pathfinder to rare earth elements
2024-09-30 08:00 - 17:00 | Kensington Lecture Theatre, WA, Australia
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S&A Colloquium: Dongjin Kim (CSIRO)
2024-09-18 15:00 - 16:00
Radio Jet and Obscuring Torus of Active Galactic Nuclei Revealed by VLBI

Abstract

Active Galactic Nuclei (AGNs) are believed to play a significant role in the formation and evolution of galaxies through their energetic jet outflows. However, observational constraints are still limited when it comes to understanding how radio jets are triggered and how jet feedback operates in different types of AGNs. To gain insights into these processes, it is crucial to study both the continuum radio jet and the circumnuclear gas in AGNs. This presentation will review high-angular-resolution VLBI studies on AGN radio jets and their immediate surroundings. Specifically, I will emphasize spectroscopic studies of AGNs using molecular absorption and highlight promising scientific opportunities that can be achieved with current and future mm/sub-mm VLBI arrays. These studies provide valuable insights into the nuclear environments of AGNs, offering a better understanding of the triggering and feedback mechanisms driving radio jet outflows.
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S&A Colloquium: Oliver Oayda (University of Sydney)
2024-08-28 15:00 - 16:00
Probing the Cosmic Dipole in the Radio Sky using ASKAP for Cosmology

Abstract

The dipole of the Cosmic Microwave Background (“CMB”) is conventionally understood to be due to our heliocentric motion through the Universe at a speed of about 370 km/s. It is therefore called the kinematic dipole. If this interpretation is correct, this motion should impact other observables, for example large-scale radio galaxy surveys surveyed up to some limiting flux density. Our motion is anticipated to induce a variation in galaxy source density described by a dipole — the “cosmic dipole”. Analysing the consistency between this dipole and the kinematic dipole functions as a test of the cosmological principle, which is the assumption that our Universe is homogeneous and isotropic on large scales. We present a Bayesian analysis of two radio galaxy surveys — RACS-low and NVSS — and find that, even after accounting for local sources, the dipole points roughly in the same direction as the kinematic dipole but has an amplitude 2 to 3 times larger than anticipated. This accords with other studies in the literature and represents an ongoing challenge to the kinematic interpretation of the CMB, and therefore the cosmological principle.
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S&A Colloquium: Pascal Keller (Leiden Observatory)
2024-08-21 15:00 - 16:00
Investigating the Epoch of Reionisation with Radio Interferometers

Abstract

The Epoch of Reionisation (EoR) marks the cosmic period during which the neutral hydrogen that pervaded the Universe transitioned to an almost entirely ionised state. The most promising probe of the EoR is the redshifted 21 cm line, which has the potential to characterise the 3-dimensional distribution of neutral hydrogen. The statistical detection of its spatial fluctuations is a prime objective of modern low-frequency radio interferometers, though instrumental systematics and calibration errors pose an immense challenge. In this talk, I will discuss a calibration-independent method of detecting the cosmological signal fluctuations using the interferometric closure phase. I discuss recent developments in the interpretation of the closure phase delay power spectrum and present constraints on it obtained from a full season of HERA observations.

Additionally, I present the results of a VLA L-Band survey of 138 optically confirmed reionisation-era quasars. The survey aimed at finding quasars suitable for measuring the cosmological 21 cm signal in absorption to their bright radio emissions. The survey was further used to constrain the statistical properties of the high-redshift quasar population and their cosmic evolution.

Together, these efforts extend the required groundwork for detecting the cosmological 21 cm signal from the EoR.
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S&A Colloquium: Orsola De Marco (AAL)
2024-08-14 15:00 - 16:00
AAL member update to CSIRO Space & Astronomy

Abstract

AAL is a not-for-profit organisation, whose members are Australian universities and institutions with a significant astronomical research capability. CSIRO Space & Astronomy is one of our member institutions and we are so pleased to be delivering our member update to you all in person once more this year. During our presentation, we will provide a quick introduction on who we are, where our funding money comes from and where it goes. We will discuss some of our key projects, the bid for full membership of ESO and AAL’s strategy moving forward over the next 12 to 24 months.
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S&A Colloquium: Laura Driessen (University of Sydney)
2024-08-07 15:00 - 16:00
The Sydney Radio Star Catalogue: a new catalogue of radio stars

Abstract

I will present a new catalogue of 839 radio stars detected < 3 GHz: the Sydney Radio Star Catalogue (SRSC). Most of these stars were identified using ASKAP. The ASKAP stars in the SRSC were found using a range of techniques: circular polarisation searches, proper-motion searches, variability searches and multiwavelength cross-matching. We have also included published radio stars from e.g. MeerKAT and V-LoTSS in the SRSC. The catalogue contains stars from across the Hertzsprung-Russell diagram, from ultra-cool dwarfs to blue supergiants to Wolf Rayets. The previous best-known radio star catalogue, the Wendker catalogue, contained 228 radio stars detected < 3GHz. Hence the SRSC is a big leap forward in our understanding of the population and characteristics of radio stars. I will present an overview of the SRSC catalogue, including the search methods, the properties and types of stars, the X-ray-radio characteristics using eROSITA_DE observations, and the circular polarisation properties. I will also highlight some individual objects of particular interest. I will also present a short summary of ASKAP VAST, with some recent updates.
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S&A Colloquium: Tasso Tzioumis (CSIRO)
2024-08-02 15:00 - 16:00
34 years with CSIRO

Abstract

On the occasion of his retirement from CSIRO, Tasso Tzioumis will look back over his 34 year career in the Australia Telescope National Facility.
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S&A Colloquium: Hao Ding (NAOJ)
2024-07-31 15:00 - 16:00
Enhancing the studies of reference frame ties and millisecond pulsar formation channels with LBA astrometry of millisecond pulsars

Abstract

Millisecond pulsars (MSPs) are the fastest-spinning neutron stars. Thanks to their superbtime-keeping ability, MSPs have provided sharp tests of gravitational theories, and have been collectively used to constrain the stochastic gravitational-wave background (GWB). Precise astrometric studies of MSPs are desired in many ways. In this talk, I will mainly focus on two scientific prospects promised by MSP astrometry. Firstly, as I will explain in the talk, the velocity distribution of MSPs is likely multi-modal. VLBI astrometry of MSPs holds the key to constraining the MSP velocity distribution, which is directly linked to the formation channels of MSPs. Secondly, VLBI and timing observations of MSPs can jointly refine the connection between the kinematic and dynamic reference frames, which would betterquantify the systematics in pulsar timing array studies. As the major VLBI network in the southern hemisphere, the Australian Long Baseline Array is crucial for significantly enriching the astrometrically studied MSP sample. I will introduce a new LBA program focusing on MSP astrometry, and update its progress. Alongside the scientific discussions, I will describe the main challenges the two studies are facing, and outline some innovations in data reduction and analysis that may help us overcome the challenges.
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S&A Colloquium: Apurba Bera (ICRAR/Curtin)
2024-07-17 15:00 - 16:00
The curious case of twin fast radio bursts detected in the ASKAP-CRAFT survey

Abstract

Fast radio bursts (FRBs) are brilliant short-duration flashes of radio emission originating at cosmological distances. Vast diversity in the properties of currently known FRBs, complex spectro-temporal structures and the fleeting nature of these events make it difficult to understand their progenitors and emission mechanism. The Commensal Real-time ASKAP Fast Transients (CRAFT) survey, with the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope, enables high time resolution spectro-polarimetric study of FRBs that helps us probe the physics of the emission source and its surrounding medium. In the currently available CRAFT FRB sample we identified two apparently unrelated FRBs that show remarkable resemblance in pulse shape, rest-frame emission time-scales and polarization properties — which indicates that these two events are likely to have very similar progenitors. In this talk I will describe the observed properties of these two FRBs and discuss their possible interpretations.
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S&A Colloquium: Patricia Forster
2024-07-10 15:00 - 16:00
Western Australia Aboriginal Astronomy

Abstract

Traditionally, Aboriginal people used objects in the sky to establish direction, guide navigation, predict seasons and as calendars for planning social life. Their narratives linked objects in the sky to life and landforms on earth and frequently included a moral element. This talk will draw on less publicized aspects of WA Aboriginal Astronomy from my review of the topic published by Cambridge University Press for the Astronomical Society of Australia.
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S&A Colloquium: Monserrat Martinez (Swinburne)
2024-07-03 15:00 - 16:00
The role of AGN in regulating galaxy evolution in massive z~3-4 galaxies

Abstract

An excess of massive quiescent galaxies (MQGs) is found at the early universe (z~3-4). MQGs at this epoch suggest their stellar content was already in place in the first 1.5 Gyr of the Universe. These findings indicate that MQGs must have experienced an event that caused rapid quenching. Although observational evidence is scarce, AGNs are the most suitable candidate for quenching these galaxies. In this talk, we present a sample of massive galaxies (10 < log(𝑀★/𝑀⊙ ) < 11) at 3 < z < 4 from JWST NIRSpec and the ZFOURGE survey with K–band spectra of the Keck/MOSFIRE, VLT/KMOS. We find that a large fraction have strong [OIII]5007 and H𝛽 emission lines with large line widths (𝜎 100 – 450 km/s). These results show a significantly high AGN fraction in massive galaxies, ranging from 60–70%, pointing to the period between 3 < z < 4 being a time of heightened activity for the development of supermassive black holes in the massive end of the galaxy population and provide evidence for their role in the emergence of the first massive quenched galaxies at this epoch.
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S&A Colloquium: Benjamin Roberts (University of Queensland)
2024-06-26 15:00 - 16:00
A brief history of time(keeping): atomic clocks at the precision frontier of fundamental physics

Abstract

Atomic clocks are the most precise instrucments ever constructed. The best atomic clocks today have a precision that corresponds to losing no more than a second over the lifetime of the universe. In this talk, I’ll discuss the role of atomic clocks at the forefront of fundamental physics, with a particular focus on dark matter, and how precision atomic physics allows us to extend the search for dark matter (and other exotic physics) to lower and lower masses. (Image credit: N. Hanacek, NIST)
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S&A Colloquium: Susmita Sett (Curtin)
2024-06-12 15:00 - 16:00
Imaging pulsar census of the Galactic Plane using MWA VCS data

Abstract

Pulsars play a crucial role in exploring a wide range of physics and astrophysics, such as probing dense-matter physics and testing strong-field gravity. Traditional pulsar surveys have mostly used time-domain periodicity searches, but these methods can be hindered by scattering, eclipses, and orbital motion, especially at low radio frequencies (<300 MHz). In contrast, image domain searches for pulsars are more effective against these effects, enabling new discoveries in the parameter space unreachable by traditional methods. To exploit the capability of image-based pulsar searches, a pipeline has been developed to form 1-second full Stokes images from high-time-resolution data (Voltage Capture System, VCS) from the Murchison Widefield Array (MWA). This led to the exploration of image-based techniques for identifying new pulsar candidates. In this talk, I will describe a low-frequency image-based pulsar census of the Galactic Plane (GP) with the MWA focused on detecting the known pulsars in the observed region of the sky using both image-based and beamformed methods. This effort led to our detection of known pulsars, with some being detected for the first time at low-frequency (150 MHz). The continuum flux densities of the pulsars detected in our image-based GP survey are significantly more reliable than the timing flux densities and therefore offer an additional benefit as flux densities are not readily available or are unreliable for many known pulsars at low frequencies. Therefore, imaging is an effective approach for discovering new pulsars in less-explored regions of the DM space and improving the spectral modelling of the known detected pulsars. Upcoming facilities like SKA-Low will enhance the success of such image-based pulsar searches and aid in identifying new pulsar candidates.
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S&A Colloquium: Evgeni Grishin (Monash)
2024-06-05 15:00 - 16:00
Stellar Death and Compact Object mergers in Galactic nuclei

Abstract

The dynamical and hydrodynamical evolution of stars and stellar remnants is greatly affected by the dense galactic nuclei (GN) environment. We explore the complex interplay of several physical processes that shape the properties, rates and environments of nuclear transients and black hole (BH) mergers and gravitational-wave (GW) events: i) We show how stellar dynamics shape the rate and properties of stellar BH and NS dynamical evolution and mergers ii) For active galactic nuclei (AGN), we study how the presence of an accretion disc modifies the light curves of exploding supernovae and their relation to other nuclear transients. iii) We examine the gravitational torques in AGN discs that drive BH’s radial migration. We find that thermal diffusion greatly alters the existence and nature of migration traps in AGN discs, which are believed to be responsible for massive hierarchical GW mergers. We find that GW mergers predominantly occur in low-luminosity AGNs. We use detailed recoil kicks and AGN models to study the efficiency of BH mergers for different generations. iv) If time permits, we show how exotic axion dark-matter theories could be constrained via pulsar timing of pulsar binaries in galactic cores.
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S&A Colloquium: Ellie Sansom (ICRAR/Curtin)
2024-05-29 15:00 - 16:00
A Global Fireball Observatory for planetary defence: a multidisciplinary approach

Abstract

When asteroids hit the Earth’s atmosphere, they produce light, heat and shock waves. Observing these phenomena, from the fireball to the seismic and infrasound, gives us a huge amount of information about the impacting object. We can calculate where they came from (their orbit), what they’re made of (geochemistry), size of the object, and even where any meteorites might land. Large, hazardous asteroid impacts are rare, and civilisation-ending events from km-sized asteroids are relatively well constrained. But, metre sized objects are still capable of posing a threat to people and property. Understanding these larger (>1 m diameters) events is fundamental to understanding the numbers of hazardous objects in the inner solar system; a key component to planetary defence. The Global Fireball Observatory is a planetary-scale observational facility for rare, fireball events occurring when asteroids hit our atmosphere. Multi-sensor observations allows us to characterise these objects and inform the size frequency distribution of near Earth objects, underlying planetary defence efforts.
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S&A Colloquium: Aman Chokshi (University of Melbourne)
2024-05-22 15:00 - 16:00
Instrumental Challenges of an Epoch of Reionization Detection

Abstract

All-sky satellite measurements of Murchison Widefield Array beams reveal significant asymmetric sidelobe distortions at an ~10% level, attributed to a range of environmental effects. In this talk I present the experiment used to carry out satellite beam measurements, and the Bayesian MCMC framework developed to incorporate these satellite measurements into a simulation test-bed to understand and propagate the effects of distorted beams on Epoch of Reionization (EoR) Science. I demonstrate how mismatches between realistically deformed beams and the perfect beam assumed during calibration lead to unavoidable spectral contamination between 100-1000 times brighter than the expected EoR signal. I also outline methods which will enable next-generation telescopes such as the Square Kilometre Array to implement parallel and affordable beam monitoring systems, facilitating the highest fidelity science outputs.
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S&A Colloquium: Kai Polsterer (HITS gGmbH, Heidelberg)
2024-05-15 15:00 - 16:00
From Supervised to Unsupervised ML: lessons learned from learning machines

Abstract

The amount, size, and complexity of astronomical data-sets is growing rapidly in the last decades. Now, with new technologies and dedicated survey telescopes, the databases are even growing faster. Besides dealing with poly-structed and complex data, sparse data has become a field of growing scientific interest. By applying technologies from the fields of computer sciences, mathematics, and statistics, astronomical data can be accessed and analysed more efficiently.

A specific field of research in astroinformatics is the estimation of the redshift of extra-galactic sources, a measure of their distance, by just using sparse photometric observations. Observing the full spectroscopic information that would be necessary to directly measure the redshift, would be too time-consuming. Therefore, building accurate statistical models is a mandatory step, especially when it comes to reflecting the uncertainty of the estimates. Statistics and especially weather forecasting has introduced and utilized proper scoring rules and especially the continuous ranked probability score to characterize the calibration as well as the sharpness of predicted probability density functions.

After presenting how this work led from well calibrated redshift estimates to an improvement in statistical post-processing of weather forecast simulations, an example of interdisciplinarity in data-science, we continue with unsupervised machine learning techniques. We start with the challenge of classifying morphologies of radio-galaxies, talk about star-formation history in LMC, discuss the difficulties in representing time-series, and end with a discussion on novel explorative science platforms for e.g. spectral data. In this part of the talk, we show-case how machine learning can be used as a machinery of discovery to access large data-sets. Several examples are presented to provide examples for the individual researchers in the audience.
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S&A Colloquium: Anna Scaife (Uni of Manchester, UK); Jayaram N Chengalur (TIFR, India); Scott Ransom (NRAO, USA)
2024-05-08 15:00 - 16:00
CSIRO Space & Astronomy Special Mini-Symposium

Abstract

This week a special mini-symposium will be held in-person at Marsfield, and on-line, with the three international members of the ATNF Steering Committee each giving a short presentation.

Scaling laws and self-supervised learning in AI for astrophysics – Anna Scaife (University of Manchester)

As the current trend in deep-learning tends towards more data, more compute and more parameters, we ask: how large can astrophysical deep-learning models get? Using the largest dataset of labelled astronomy data available, we examine the scaling laws for supervised problems in astrophysics and conclude that self-supervised learning is a more promising direction for large-scale deep-learning in astronomy given the available label volumes; however, we also conclude that using in-domain (astronomy) data for pre-training results in better performance for the down-stream tasks from these self-supervised representations. Finally, I will show how we are building self-supervised foundation models for radio astronomy and a variety of the downstream tasks where we have applied them in practice.

The evolution of the HI content of galaxies – Jayaram Chengalur (TIFR)

Over cosmic time, galaxies grow by merger, and/or by the accretion of matter via inflows. As galaxies evolve they also convert their gas into stars. On a cosmic scale, it is well established that the star formation peaked about 10 billion years ago and that the average star formation rate per unit volume has declined sharply since then. Hydrogen is dominant baryonic component of galaxies, and atomic hydrogen is also the primary fuel for star formation. Stars form as the gas cools to become molecular hydrogen, and then cools further and collapses into stars under self gravity. Understanding the evolution of the atomic hydrogen content of galaxies is hence key to understanding the evolution of the star formation rate with cosmic time. The recent upgrade to the Giant Metrewave Radio Telescope (GMRT), has allowed significant progress to be made in observing HI in galaxies at redshifts around 1 using the stacking method. In this talk, I will discuss some of the results from ongoing atomic hydrogen surveys of star forming galaxies using the upgraded GMRT.

New Exotic and Massive Pulsars in Globular Clusters – Scott Ransom (NRAO)

In the past five years, the number of known globular cluster pulsars, most of them of the millisecond variety, has blossomed by more than 130 to a total of over 300. The main reasons were the commissioning of the extremely sensitive FAST and MeerKAT radio telescopes, and increased computing power applied to the searches themselves. In this talk I’ll mention some of the fascinating exotic systems that have been found, discuss the importance of long-term timing of these systems, and hint at the astrophysics and basic physics those systems will provide.
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S&A Colloquium: Ophelia Renaud (INSA-IETR, France)
2024-04-24 15:00 - 16:00
Design and programming of heterogeneous and high-performance computing systems in astronomy

Abstract

In this presentation, I address the difficult problem inherent in SKA of deploying complex astronomical applications under development on efficient target architectures that have not yet been built. Resource allocation in such scenarios has a significant impact on multiple factors such as latency, memory, energy, and cost among others. Solutions such as rapid prototyping make it possible to reliably simulate and generate efficient code for this purpose. At INSA-IETR, we are developing the PREESM rapid prototyping tool to automate and accelerate this process. The tool is based on numerous thesis and internship projects as well as numerous collaborations such as Rising Stars, which is the subject of my presentation. This presentation will give an overview of the project’s progress in our team. I propose methods based on the SDF (Synchronous Dataflow) model and clustering techniques to facilitate the deployment of applications on complex architectures such as CPUs, GPUs, and FPGAs on one or more machines. By providing a quick and easy solution to this NP-hard problem, our methods significantly improve the efficiency of astronomical application deployment.
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S&A Colloquium: Jordan Collier (AusSRC/CIRA)
2024-04-17 15:00 - 16:00
Clouds over middle-earth: using ilifu to combine the MeerKAT and the EMU for ORCs

Abstract

Combining ASKAP’s EMU survey and MeerKAT enables complementary science; ASKAP’s large FoV enables the discovery of new/rare types of objects, like Odd Radio Circles (ORCs), while MeerKAT’s sensitivity enables deep follow up of such objects. I will speak about both instruments and how they are being used to open up new phase spaces of discovery, with a particular focus on the spectral indices and polarisation of ORCs, and my experience using these telescopes within the clouds across the continents of middle-earth! As an essential part of this research, I will speak about a number of tools and systems that have been developed or adopted to deal with the PB scale of MeerKAT data at the Inter-University Institute for Data Intensive Astronomy (IDIA). I will present a number of these tools and underlying systems, deployed on IDIA’s ilifu facility, including those for storage, processing, visualisation, and data transfers.
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