I'll introduce a new class of radio objects, the Odd Radio Circle (ORCs). You'll learn why they're odd; how far away they are; and some ideas for what may produce them, based on recent optical spectroscopy.

Accretion disks are common in astrophysical systems, from AGN to protostellar disks. The disks of Be stars (rapidly rotating Main Sequence B-type stars) are special: they are discretion disks, built from matter ejected by the central object. When in a binary system, the companion can affect the Be disk in many ways, exciting density waves and even causing truncation. It can also accrete material from it, as is the case for Be X-ray binaries, whose X-ray emission is powered by accretion onto a compact companion. In our work we simulate Be binaries with a smoothed particle hydrodynamics (SPH) code (Okazaki et al. 2002) in order to investigate the effects of the companion on the dynamics of the disk, the process through which it accretes matter, and how the system loses mass as whole. We employ a modified version of the code, specially updated by us to increase resolution in low density areas of the system, such as the outer disk and around the companion. We find that disks are formed around the secondary in all models, but viscosity, mass ratio and period play a significant role in their structure and kinematics. A circumbinary disk is formed around the system for all simulations, which was never before seen in simulations for coplanar, circular Be binaries, but agrees with recent observational findings of radio emission from these types of system, where an ad-hoc circumbinary disk model was employed. Our study paves the way for a better understanding of X-ray emission in Be X-ray binaries, and offers an insight in how hidden companions of Be stars can be detected observationally.

The Northern Light has been inspiring awe in humans for millennia. We mostly see three colors of light dancing in the sky: Blue aurorae at 428 nm coming from excited N2, Green aurorae at 557.7 from atomic oxygen, and red aurorae mainly at 630 nm also due to atomic oxygen. Interest in the polarization of the northern light started in 1959, but the reported measurements were quickly disputed and the results were deemed unreliable. Interest in this topic has been low, until 2008, when they again observed the red line of the Aurora and found a significant signal. However, this and the following polarization measurements of the other lines lacked spatial information. In this talk, I will present measurements of the polarization of the Aurora with our new compact instrument which can do RGB linear polarization measurements. I will discuss the main obstacles we faced, solutions such as adding an additional halfwave plate, and a preliminary view of the latest results.

I will present one of the most recent climate simulation results regarding the potential collapse of one of Earth’s most prominent tipping elements: the abrupt collapse of the Atlantic meridional overturning circulation (AMOC). AMOC is a system of ocean currents that brings warm water north and cold water south in the Atlantic. Its potential collapse could lead to abrupt cooling of the Northern Hemisphere, changes in tropical rainfall patterns, and non-linear changes in sea-level rise in the North Atlantic. Using the Community Earth System Model, Van Westen et al. (2024) simulated the first AMOC tipping event due to ocean freshwater forcing from Greenland Ice Sheet melt. From their results, they developed a physics-based and observable early warning signal of AMOC tipping. Atmospheric reanalysis products indicate that the present-day AMOC is on route to tipping, but current time series measurements do not allow us to predict when this abrupt transition might occur. Abrupt transitions occurring due to climate change might have a dramatical impact on ecosystems and living organisms on our planet.

Van Westen et al., Sci. Adv., 10, 6, 2024

The chemical evolution of distant galaxies, unlike nearby galaxies, cannot be assessed from observations of individual stars. On the other hand, the study of the interstellar medium (ISM) is an alternative way to reveal important properties of the chemical evolution of distant galaxies. The outcome of the evolutionary history of galaxies is recorded in the interstellar abundances of the chemical elements. Observations of the interstellar medium (ISM) in galaxies of various types, which differ in mass, size, metallicity, and are at different evolutionary stages, can provide a key to understanding the processes taking place in galaxies.I will present the study of the abundance patterns of the neutral ISM in 110 gas-rich mostly-metal-poor distant galaxies (Damped Lyman-alpha absorbers, DLAs) at redshifts 0.60 < z < 3.40. We observe systematic deviations from the basic abundance patterns for O, Mg, Si, S, Ti, and Mn, which we interpret as alpha-element enhancements and Mn underabundance.  We constrain for the first time the distribution of the alpha-element enhancement with metallicity in the neutral ISM in distant galaxies. Less massive galaxies show an alpha-element knee at lower metallicities than more massive galaxies. If this collective behaviour can be interpreted as for individual systems, this would suggest that more massive and metal-rich systems evolve to higher metallicities before the contribution of SN-Ia to [alpha/Fe] levels out that of core-collapse SNe, possibly explained by different SFR in galaxies of different masses. Overall, our results add important clues to the study of chemical evolution of distant galaxies.

Pressure broadening is one of the general line broadening processes in astrophysics. Indeed, it is widely used to model spectra from stelar and exoplanetary atmospheres, where the gas pressure is significantly high. However, its effect has been ignored in the field of planet formation. In this talk, we show that pressure broadening can affect line emission with high optical depths, even under a typical condition of the inner ~10 au region of protoplanetary disks, which produces very broad line wings. By taking advantage of this phenomenon, we can directly measure the gas pressure and density, which is otherwise a very difficult task. Indeed, we found that the CO molecular line spectrum from the nearest protoplanetary disk around the young star TW Hya has a very broad line wing, which is characteristic of pressure broadening. We successfully derived the gas density profile and found that the disk is gas-rich and a promising site for planet formation.

An ESO internal ALMA development study, BRAIN is addressing the ill-posed inverse problem of image analysis employing astrostatistics and astroinformatics [1,2]. These emerging fields of research offer interdisciplinary approaches at the intersection of observational astronomy, statistics, algorithm development, and data science [3]. In this study, we provide evidence of the benefits in employing these approaches to ALMA image analysis for operational and scientific purposes. We show the potentials of two techniques (RESOLVE [4,5] and DeepFocus [6]), applied to ALMA calibrated science visibilities. Significant advantages are provided with the potential to improve the quality and completeness of the data products and overall processing time. Both approaches evidence the logical pathway to address the incoming revolution in data analysis dictated by ALMA2030 [7]. Moreover, we bring to the community additional products through a new package (ALMASim) to promote advancements in these fields, providing a refined ALMA simulator usable by a large community for training and/or testing new algorithms.

[1] Guglielmetti, F. et al. "Bayesian and Machine Learning Methods in the Big Data Era for Astronomical Imaging" Phys. Sci. Forum 2022, 5(1), 50; https://doi.org/10.3390/psf2022005050

[2] Guglielmetti, F. et al. ?A BRAIN Study to Tackle Image Analysis with Artificial Intelligence in the ALMA 2030 Era? Phys. Sci. Forum 2023, 9(1), 18; https://doi.org/10.3390/psf2023009018

[3] Siemiginovska, A. et al. "Astro2020 Science White Paper: The Next Decade of Astroinformatics and Astrostatistics", arXiv 2019, arXiv:1903.06796

[4] Junklewitz. H. et al. "RESOLVE: A new algorithm for aperture synthesis imaging of extended emission in radio astronomy", A&A, 586, A76 (2016)

[5] Tychoniec, L. et al. "Bayesian Statistics Approach to Imaging of Aperture Synthesis Data: RESOLVE Meets ALMA" Phys. Sci. Forum 2022, 5(1), 52; https://doi.org/10.3390/psf2022005052

[6] Delli Veneri, M. et al. "3D detection and characterization of ALMA sources through deep learning", 518, 3 (2023); https://doi.org/10.1093/mnras/stac3314

[7] Carpenter, J.; Iono, D.; Kemper, F.; Wootten, A. "The ALMA Development Program: Roadmap to 2030", arXiv 2020, arXiv:2001.11076

Supervised learning methods are routinely used on tabular data of light-curves (either feature based or involving deep learning) to classify the origin of the variations. On the other hand, a not so commonly used approach is to classify the phased curves as "static" images themselves. We are not the first group to propose this approach but since it is still not commonly used I will present the main challenges and achievements we faced from a conceptual point of view. As this is meant to be an informal discussion, some intuitive principles will be explained regarding how our architecture works, how data have to be (and are) processed, etc

I will present some of my experiences moving from engineering to Astronomy. Some of the advantages and disadvantages of this change and also some differences between the two fields I've seen along the way. It was a good idea? We will see...

We will reminisce about the what happened leading up to the discovery of the accelerated expansion and what it took to get there. Some of the consequences of this discovery will also be presented.

Orbyts is a multi-award-winning movement that partners scientists with schools to empower school students to undertake world-leading research. We aim to address diversity issues in science and to support short-supply science teachers who have extensive time pressures. We accomplish this through multi-term partnerships that are proven to transform science inclusivity, inspire school students and teachers, and ignite scientists' leadership potential. In this discussion I will explain how the Orbyts programme works on a practical level, and share some of the highlights of our most recent impact report.

Open Access (OA) publishing has become a hot topic. Funders, research organisations, and universities are developing OA policies that researchers need to know about and adhere to. The fact that models for OA implementation vary and continue to evolve makes it difficult to stay well informed.

In this Informal Discussion, we will review the situation in OA publishing by looking at positive, but also negative aspects, along with a few issues that should be avoided altogether. We will also look at the OA models of major astronomy journals and evaluate if and how they are suited to establish a collaborative, equitable, sustainable publishing landscape.

In today's dynamic landscape, where efficiency and innovation are pivotal, the Julia programming language (https://julialang.org/) demonstrated to be a revolution in scientific and data computing. This programming language got attention for its exceptional speed, versatility and easy to use. In the same line of Python, Julia is used in fields as diverse as finance, healthcare, engineering in addition to be widely used in particle physics. Oliver Schulz (MPP), developer of BAT.jl (Bayesian Analysis Toolkit), will provide a general introduction, background, and some pros and cons of Julia programming language.

Important note, this discussion will continue with some worked examples in the AI Forum at 14:00 (10/01/2024).