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Raj's CoC

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The last five years have witnessed a substantial number of new
observational manifestations for magnetars, encompassing fast radio
burst (FRB) associations, the detection of giant flares in extragalactic
magnetars, high cadence observations of glitch epochs, and new X-ray
polarization information from IXPE. These have seeded both a growth in
understanding, and also a magnification of their mysterious character.
This talk summarizes some recent observational and theoretical advances
that address signals from their magnetospheres. First up, the
occurrence of FRBs in the Galactic magnetar SGR J1935+2154 will be
discussed, with one in association with a double glitch that is
interspersed with a rapid spin-down epoch that might be driven by a
strong, ephemeral wind. Opacity considerations for magnetar bursts and
persistent hard X-ray emission may impact our understanding of where
FRBs must be generated in magnetar magnetospheres. Next, the detection
of magnetar giant flares outside the Milky Way allows for the tracking
of spectral evolution, which can be explained by Doppler beaming due to
the star's rotation. Understanding these powerful events can inform the
environmental conditions for the winds that may be associated with
glitches that arise near some magnetar FRBs.

Although the concordance ?CDM model is mostly consistent with observations, some key components, such as dark matter and dark energy, still need to be understood at the fundamental level. Understanding how the tiny initial density fluctuations in the early universe evolve into the distribution of galaxies in the sky today provides us with more clues on the nature of dark matter and dark energy. Two of the most powerful methods for extracting information about the large-scale structure of the universe are through analysing the distribution of galaxies and their peculiar velocities. In this talk, I will describe various methods for constraining cosmological parameters using the galaxy power spectrum. I will also explain how such methods could be sped up for new galaxy surveys such as DESI. Finally, I will explain how the use of peculiar velocities of galaxies can complement their distributions to obtain tighter constraints on the growth rate of structure.

Recent research by others has shown that CI, CO and dust are
all valid methods of tracing molecular hydrogen. I show that all
three methods give surprisingly consistent results at high redshift,
but with evidence that in some high-redshift galaxies the calibraton
factors for all threee tracers are severa times less than at low redshift.
Using dust as the tracer, I show that the mean dust density in the universe
depends on redshift in a similar way to the star-formation density.
I then summarise the early results on galaxy evolution from the
Euclid Q1 data release, with a look forward to the DR1 data release.
I then describe some new methods to investigate galaxy evolution
in the era of billion-galaxy surveys. Using COSMOS as an sandpit to
test them, I show some intriguing early results.

Processing large astronomical datasets is essential for modern astrophysics and relies on compute-intensive pipelines deployed on High-Performance Computing (HPC) infrastructure. While these infrastructures are necessary for handling vast amounts of data and extensive CPU time, their programming can be challenging for non-computer scientists. Scientific workflow systems like Nextflow and DaLiuGe provide high-level scripting interfaces that simplify the design and deployment of highly parallel pipelines on multi-node HPC infrastructures.
A key challenge is predicting and optimizing the computing resources required to execute these pipelines. Given the shared nature of HPC systems, it is crucial to ensure that resource reservations closely match actual utilization. However, predicting resource utilization is complex due to the flexible computational models used in scientific workflow systems.

Leveraging experience from parallel embedded systems programming with dataflow models of computation, this work aims to build a statistical model of Nextflow's pipeline performance using previous execution traces. The objective is to predict key timing and memory characteristics of individual jobs within a pipeline, optimize resource reservations, monitor pipeline progress in real-time, and provide latency estimations for different HPC system architectures.
The proposed workflow has been extensively tested on the CELEBI Pipeline for Fast Radio Burst localization using the OzStar infrastructure, demonstrating significant improvements in resource utilization and pipeline efficiency.

TL;DR: Why is a French researcher in embedded system design automation is visiting an astronomy research center down under for 5 months?

Core-collapse supernovae (CCSNe) mark the violent deaths of massive stars and are among the most energetic explosions in the Universe. These catastrophic events are responsible for the formation of the neutron stars and black holes observed through gravitational waves. In recent years, CCSNe have emerged as key targets for gravitational-wave detection, offering a unique window into the central mechanism that powers these explosions. This talk will discuss the latest developments in CCSN numerical simulations, including the impact on the birth properties of black holes and neutron stars observed through gravitational waves, the latest CCSN gravitational waveform models, and the potential for current and next-generation gravitational-wave detectors to extract astrophysical and nuclear physics insights from these events.

The structure of galaxies we see in the sky today was seeded in the very early universe. The evolution from initial tiny density perturbations to the cosmic web of voids, clusters and filaments of galaxies tells us about what the universe is made of. There are many ways to utilise this large scale structure to probe cosmology, but measuring the growth rate itself in the nearby universe is particularly powerful. We now have access to a large set of galaxy and velocity data, with much more to come in the near future from various different surveys. Using these new and upcoming data, we may be able to distinguish between the effects of basic cosmological constant dark energy or modifications to our theory or gravity.

Ashwathi Nair MCR Review

CoC

Probing the cosmic web with Fast Radio Bursts

Improving tests of fundamental physics with Very Long Baseline Interferometry of millisecond pulsars.

Low- and intermediate-mass stars disgorge their outer layers during the asymptotic giant branch (AGB) phase, one of the last stages of their lives. Material containing newly-formed elements and a variety of dust and molecules streams out of them in what we call a stellar wind. Studies resolving the extended circumstellar environments of AGB stars have revealed spirals, discs and bipolar outflows, with the shaping of the gas attributed to interactions with a companion. However, most of these companions are not directly observed, because their light is so strongly attenuated by the dust created around the AGB star. Astrochemistry is the study of molecules, dust and the chemical reactions that link them in astrophysical environments. I will discuss new methods that combine theoretical astrochemistry with observations to allow us to deduce the nature of the companion stars in binary systems with AGB stars. From this we can begin to understand how companion stars affect the length of the AGB phase.

The dark energy which fills the Universe appears to be evolving with time, according to recent results published by the Dark Energy Spectroscopic Instrument (DESI) collaboration, in a joint analysis with supernova datasets. In this talk I will discuss: What is DESI? How does it measure the effect of dark energy? What does it mean for the properties of dark energy to "evolve", and is this related to the more famous "Hubble tension"? And what should we make of these intriguing results?

Cold (<100 K) gas and dust are essential ingredients for galaxies to form stars. Over the last two decades, constraining gas and dust content has been one of the key scientific drivers of submm/mm interferometry observations (such as the Atacama Large Millimeter/submillimeter Array (ALMA) and Northern Extended Millimeter Array (NOEMA)). Meanwhile, the James Webb Space Telescope (JWST) starts unveiling more quiescent (massive) galaxies at z>3 and allows a detailed study of z>~1.5 quiescent galaxies more efficiently. Intriguingly, not all of these quiescent galaxies are devoid of gas and dust. In this talk, I will talk about gas and dust measurements in star-forming and quiescent galaxies in the early universe (z~1 or higher, or when the age of the universe was less than ~ 6 Gyrs) and the implications. The talk will also cover a recent effort of ALMA archival data mining, called ECOGAL (ECOology for Galaxies using ALMA archive and Legacy surveys), to improve the current gas scaling relation – gas depletion time scale as a function of stellar mass, redshift and deviation from the main sequence – across cosmic time and space.

https://anu.zoom.us/j/85375551314?pwd=NnNtbHNieUZodEx6UmpweGoreDFodz09

Saurav CoC review.

Saurav's CoC committee meeting

I will discuss some of the major ideas behind galaxy formation
simulations. Detailed numerical simulations are critical to interpret and
understand observations. Unfortunately, simulations are sensitive to feedback
implementations. Interactions at wind/halo gas interfaces in the CGM occur on
scales that are much below the resolution of any current or near future galaxy
formation simulation, making a "brute force" approach not viable. To mitigate
this impasse implemented a new wind algorithm, Physically Evolved Winds (PhEW),
which explicitly models the "subgrid physics" in the wind-halo gas interaction
within a simulation, tuned to very high resolution simulations of clouds moving
through the CGM/IGM, using the cosmological simulation to provide the physical
characteristics that informs the interaction. Previous simulations using more
standard wind model approaches reproduce many observed properties of galaxies
but our new wind implementation allows us to tie empirical successes, and
failures, more securely to the underlying wind physics and to make more robust
predictions. I will show the first results of simulations using this new
feedback method, whose results are much more robust to changes in the hydro
method and numerical resolution.

https://swinburne.zoom.us/j/81452278865?pwd=M0m1ho7TNBCPkRb6ElMIxPIIgMbC8G.1
Password: 523082

Searching for Fast Radio Bursts with ASKAP

We use state-of-the-art cosmological hydrodynamical simulations of galaxies to study recent ‘hot topics’ in galaxy formation at the smallest scales: the existence of low-surface-brightness, ultra diffuse galaxies, and the role of AGN feedback in the evolution of dwarfs.

Understanding dark matter and dark energy, which make up 95% of the Universe, requires cosmological surveys to achieve percent-level precision. Yet, this precision reveals tensions between observations and the standard cosmological model, potentially stemming from systematic biases. CLONES (Constrained LOcal & Nesting Environment Simulations) are digital twins of the local Universe designed to replicate our cosmic environment and tackle these challenges. Highlighting key cosmological tensions and showcasing a few example studies of these CLONES will demonstrate how they can offer a powerful framework for bias-free analyses, advancing our understanding of galaxy evolution and large-scale structure formation.

Using state-of-the-art reduction methods, we analyze the new JWST data acquired by the NIRISS/NIRCam wide-field slitless spectroscopy (WFSS) and NIRSpec in both the multi-object spectroscopy (MOS) and slit-stepping modes. These complementary spectroscopic data sets obtained from multiple instruments open up key window on unbiased investigation of star formation, feedback, and ISM properties in and beyond the cosmic noon epoch. We bring forth the first spatially resolved analysis of high-redshift galaxies with JWST WFSS and measure the first gas-phase metallicity radial gradient with sub-kpc resolution at z?3. We extend such analysis to galaxies in the epoch of reionization, finding a swift mode transition of galaxy mass assembly and chemical enrichment in the early Universe. We invent a novel methodology of conducting 3D spectroscopy of galaxies by stepping the NIRSpec slits across their surfaces, obtaining resolved chemical and dynamical properties for a sample of 26 galaxies at z~1 and finding clear evidence for strong rotational support in galaxies showing negative metallicity gradients. Using the NIRSpec MOS in prism mode, we discover one of the highest redshift galaxies, spectroscopically confirmed at z=8.16, with PopIII-like stellar populations. This galaxy candidate hosting the first generation stars opens up new key frontiers on galaxy evolution and stellar physics in the early Universe.