MCR review for Lydia Haacke.

Online only DTR for Luisa Buzzo. Zoom details TBD.

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Update on AAL activities

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Pulsars are a type of rotating neutron star that possess some of the strongest magnetic fields in the Universe. They emit highly polarised radio waves from regions above their magnetic poles, where the smooth change in linear polarisation state can be used to infer their magnetic geometry. Yet many pulsars display unusual deviations from these expected changes in polarisation. It has been proposed that such behaviours may be related to propagation through the extreme magneto-ionic environments that surround neutron stars, something that has been largely unexplored. In this talk, I will describe several recent advancements in polarimetric modelling and their application to high sensitivity pulsar observations obtained using Murriyang, the 64-m Parkes radio telescope. This includes the discovery and characterisation of a rare propagation effect in the unstable magnetic field of a radio-loud magnetar, and on-going efforts to determine the origins of circular polarisation and orthogonal-mode jumps across the pulsar population.

The ASKAP First Large Absorption Survey in HI (FLASH) is a large-area search for neutral hydrogen (HI) in and around distant galaxies at redshift 0.4 < z < 1.0, a cosmic epoch where our knowledge of the HI content of galaxies remains patchy and incomplete.

FLASH has two main science goals: to probe the evolution of the neutral gas content of galaxies, and to investigate gas accretion and feedback processes in active galactic nuclei. Radio searches in the HI 21-cm line are unaffected by dust extinction, and FLASH provides one of the first genuine ‘HI-selected’ galaxy samples at intermediate redshift. I will give an update on the current status of the survey (which has so far covered around 3000 square degrees of the southern sky), present some new science results from papers recently submitted or in preparation, and discuss the optical properties of the HI host galaxies. I will also outline the prospects for the full (24,000 square degree) ASKAP FLASH survey which is due for completion in 2028.

This review is online only.

We study the SDSS-IV MaNGA database consisted of spatially resolved spectra of ~10,000 galaxies to understand the emission properties of the associated ionizing sources. With the help of the BPT diagrams’ classification scheme, we train Spender (Melchoir et al 2021) to distinguish between the different spectra based on the dominant ionizing mechanism with information from the spectra outside of the strong emission lines usually used for classification. We find that a large fraction of LINER-like emission spectra can be distinguished by stellar absorption features associated with an old, metal-rich stellar component. This consistent with previous work finding that LINER emission could be driven by a stellar population of old low-mass evolved stars.

Ashwathi Nair COC Review: Formation channels of heavy binary neutron stars

The first observations with the James Webb Space Telescope (JWST) have uncovered a surprising and substantial population of compact red objects at high redshift (z = 4-9), previously undetected in even the deepest Hubble data. Subsequent ultradeep spectroscopy from the UNCOVER program revealed that these objects, colloquially known as "little red dots," exhibit ubiquitous broad Balmer lines and likely host powerful active galactic nuclei (AGN). If so, we may have identified up to 99% of known AGN at z > 4. But these are not your garden-variety type 1 QSO; their properties are weird, with some estimated black hole masses comparable to the stellar masses of their host galaxies, while in other cases the spectra display clear Balmer breaks, indicative of massive evolved stellar populations. I will present what we know so far about our new intriguing little friends, and discuss implications for our picture of early galaxy and supermassive black hole evolution.

We are currently in the fourth observing run (O4) for LIGO-Virgo-KAGRA (LVK). So far, the number of gravitational-wave candidates has almost doubled compared to the total number of events reported from the first three observing runs combined. The properties we infer from these observations have broad implications for the physics and evolution of massive stars, supernova mechanisms, our understanding of different sub-populations of compact binary systems, chemical enrichment of heavy elements in the Universe, and more. Recently, the LVK announced the detection of an exceptional event from O4: it's time to meet GW230529. In this talk, I will present the properties of this compact binary and discuss the astrophysical implications of this event.

Understanding how chemical elements are distributed in time and space across the universe provides key observational markers for the first stars. I'll summarise my team's recent efforts in tracing elements in the early universe using ESO/VLT/X-shooter via the EXQR-30 survey of intervening metal absorbers towards 42 z~6 quasars. With the benefit of the long lever arm from z=1.9 to 6.4, high sensitivity, resolution and significant number statistics, we have made meaningful inroads. Metal ions trace both chemical enrichment and the ionization state of the Circumgalactic Medium (CGM). We find that the ionization of the CGM differs significantly over the short period of cosmic time from redshift 5.5 to 6. I'll show how a decline in the incidence of intervening CIV absorbers, coupled with a rise in CII and OI complements current evidence for a late reionization continuing to occur in metal-enriched and therefore biased regions of the Universe. A flat evolution in weak MgII is also found, despite a decline in cosmic metal content. Finally, in direct comparison with JWST, I will demonstrate why medium resolution ground-based spectroscopy is essential for a complete census of the high-z CGM.

In this presentation, we 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. We 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.

Akhil's CoC review talk.

The majority of the baryons in the universe are in diffuse gaseous form and the quest to understand how the gas transitions to star formation fuel in a galaxy continues. I will discuss several projects that use observations and simulations to further understand this process (letting the audience choose which they would like to hear about). 1. How can we associate the phases of gas observed with different methods? 2. Are the cold clouds within a dark matter halo growing or being destroyed? 3. What does the interface between the disk and halo look like in simulations?, 4. Do dwarf galaxies have a CGM and what happens to it as a satellite galaxy?, 5. Related to the previous question, what is the census of gaseous satellites around spiral galaxies in the local Universe compared to the Local Group?

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 mergers, extreme mass ratio inspiral (EMRI) and tidal disruption events (TDE). ii) For active galactic nuclei (AGN), we study how the presence of an accretion disc modified the light curves of exploding supernovae and their relation to other nuclear transients. iii) We examine in detail the gravitational torques in AGN discs that drive BH's radial migration. We find that thermal torques greatly alter 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. Finally, We combine the AGN disc modelling with merger recoil kicks to further explore the parameters space and constrain the efficiency of BH mergers for different generations.

We are living in a golden age of extragalactic astronomy: observations over broad wavelength ranges, wide fields and unprecedented depth are allowing us to uncover important details on the formation and evolution of galaxies. Yet, key quantitative aspects on the properties of galaxies remain not well constrained. The most important such aspects are the stellar mass, the star formation efficiency (how much of the initial reservoir of gass is turned into stars), and the dark matter distribution of galaxies. Lack of precise knowledge on these quantities is limiting our progress in both galaxy evolution and cosmology.
Gravitational lensing is one of the most reliable tools to measure galaxy masses at cosmological distances, and therefore offers a solution to this problem. Ongoing and upcoming missions such as Euclid and the Chinese Space Station Telescope (CSST) will enable the discovery of tens of thousands of strong lenses, opening up the era of statistical strong lensing. I will discuss the opportunities that statistical strong lensing will bring for our understanding of galaxies, as well as the challenges associated with it.

The Universe started without the heavy elements that make the complexity of our surrounding world (e.g. carbon, oxygen). In this talk, I will showcase ground-breaking advances in the numerical modelling of how these chemical elements are produced in stars, how they are dispersed around galaxies by energetic events, and how they get ionized to power the emission and absorption lines we observe in the spectra of distant objects. Leveraging these new prediction capabilities will take us from interpreting the highest-redshift emission lines observable by JWST to the most local chemical abundances of Galactic stars, shedding a new light on how metal-poor stars enriched the Universe in the process.

When talking about interference sometimes the point gets a bit fuzzy. Do we lock onto the physics of waves? Or particles? Or somehow use both? My PhD has focused on developing appropriate language, activities and more to remove most of the challenging questions we face when talking about quantum science. I have developed a series of lessons for Year 9 students (aged 14-15) and their science teachers, that step them through the uncertainty in interference. Concepts covered include photons as packets of light energy, wave and particle models (including an improved description), probability, and momentum. The activities form a sequence of lessons from Year 3 to 10 as part of the Einstein-First program. Through tests and interviews I have found that the students understanding changed because of the program. Students became more certain in their understanding of the uncertainty of quantum science.

Observations of stellar nurseries, and massive stars and their fates have led to stellar evolution models of ever-increasing complexity. These models also predict the existence of stars with more than 100 solar masses, which may have no analogues in the local Universe, and exotic types of stellar explosions. One of those predicted, yet not securely discovered object classes, are pair-instability supernovae (PISNe). Confirming or refuting their existence and measuring their properties are critical for stellar evolution theory, supernova science and gravitational wave astronomy. In this talk, I will give an overview of the current search efforts for PISNe, discuss the properties of the most promising candidate and the challenges it imposes on theoretical models and how we can leverage that to find PISNe with the Vera Rubin Observatory Legacy Survey of Space and Time and upcoming space missions.

We have collected stellar spectra for more than 210 million stars in our galaxy. In this talk I will argue that there is good reason for that: stellar spectra are uniquely informative tracers of cosmic evolution. The age and composition of stars trace the formation of the universe across many orders of magnitude in both space and time. For example, in our local neighbourhood the most ancient stars can tell us about star formation at redshifts higher than what is possible with JWST, and the more common stars are explaining missing physics in stellar evolution, nucleosynthesis, and planet formation. I will describe our efforts to collect even more spectra through SDSS-V. I will include some stunning results from the new Local Volume Mapper instrument. And I'll explain some broadly applicable data analysis methods that we have developed to enable this stellar science.