Europe has become a global leader in optical-near infrared astronomy through excellence in space and ground-based experimental and theoretical research. While the major infrastructures are delivered through major national and multi-national agencies (ESO, ESA) their continuing scientific competitiveness requires a strong community of scientists and technologists distributed across Europe’s nations. OPTICON has a proven record supporting European astrophysical excellence through development of new technologies, through training of new people, through delivering open access to the best infrastructures, and through strategic planning for future requirements in technology, innovative research methodologies, and trans-national coordination. Europe’s scientific excellence depends on continuing effort developing and supporting the distributed expertise across Europe - this is essential to develop and implement new technologies and ensure instrumentation and infrastructures remain cutting edge. Excellence depends on continuing effort to strengthen and broaden the community, through networking initiatives to include and then consolidate European communities with more limited science expertise. Excellence builds on training actions to qualify scientists from European communities which lack national access to state of the art research infrastructures to compete successfully for use of the best available facilities. Excellence depends on access programmes which enable all European scientists to access the best infrastructures needs-blind, purely on competitive merit. Global competitiveness and the future of the community require early planning of long-term sustainability, awareness of potentially disruptive technologies, and new approaches to the use of national-scale infrastructures under remote or robotic control. OPTICON will continue to promote this excellence, global competitiveness and long-term strategic planning.

Nuclear astrophysics studies the origin of the chemical elements: from the Big Bang, to stellar burning, and to neutron star mergers. ChETEC-INFRA networks the three types of infrastructures that, together, provide the capabilities needed for this quest: astronuclear laboratories supply reaction data, supercomputer facilities perform stellar structure and nucleosynthesis computations, and telescopes and mass spectrometers collect elemental and isotopic abundance data. ChETEC-INFRA will overcome existing barriers to progress: Specifically, we will unify access to nuclear astrophysics research infrastructures using a novel integrated web portal. We will develop improved nuclear reaction targets and detectors, open-source nucleosynthesis software tools, and three-dimensional model atmospheres for stellar spectral analysis based on up to date physics. We will pioneer complementary techniques to address the same science case, and we will link telescopes to nuclear labs and supercomputers. ChETEC-INFRA provides the community with the tools needed to address key questions on solar fusion, neutron capture nucleosynthesis, and explosive stellar processes. In a combined approach designed to facilitate and boost accessibility, synergies and training, the large amount of transnational access provided will enable projects exploiting at least two different types of infrastructures. Within ChETEC-INFRA, data are archived and catalogued for long-term sustainability beyond the end of the project, ranging from evaluated nuclear reaction rates to detailed abundance data for a multitude of stars to tracer nucleosynthesis calculations. ChETEC-INFRA will reach out to PhD students, secondary school students, and to the detector industry. The ChETEC-INFRA community builds on the success of the ChETEC COST Action CA16117 (Chemical Elements as Tracers of the Evolution of the Cosmos). ChETEC-INFRA is networked with the nuclear astrophysics communities in the United States, China, and Japan.

We propose a conceptual design study of an innovative 10-m class wide-field spectroscopic survey telescope (WST) with simultaneous operation of a large field-of-view (5 sq. degree) and high multiplex (20,000) multi-object spectrograph facility with both medium and high resolution modes (MOS), and a giant panoramic integral field spectrograph (IFS). The ambitious WST top-level requirements place it far ahead of existing and planned facilities. In just 5 years of operation, the WST MOS will target 250 million galaxies and 25 million stars at medium resolution + 2 million stars at high resolution, and 4 billion spectra with the WST IFS. Through spectroscopic characterization, WST will potentiate the understanding of the data from many other huge imaging surveys that merely detect and classify sources. WST will achieve transformative results in most areas of astrophysics: e.g. the nature and expansion of the dark Universe, the formation of first stars and galaxies and their role in the cosmic reionisation, the study of the dark and baryonic material in the cosmic web, the baryon cycle in galaxies, the formation history of the Milky Way and dwarf galaxies in the Local Group, characterization of exoplanet hosts, and the characterization of transient phenomena. WST telescope and instruments will be designed as an integrated system and mostly use existing technology, aiming to minimize its carbon footprint and impact on local environment. Our ambition is to make WST the next large ESO project after the 40m ELT. ESO is the major inter-governmental organization for European astronomy with a unique suite of large telescopes in Chile. We will perform the study together with Australian colleagues, who have an ongoing strategic partnership with ESO and plan to apply soon for full membership. We have formed a large consortium of very experienced institutes plus ESO, representing 9 European countries and Australia. The team brings 60 years of in-kind staff effort to the study.

The aim of this ambitious research project is to produce the most realistic computer simulations of the assembly of gaseous protoplanetary accretion discs, and to understand which of their traits are inherited from and/or affected by their direct interstellar context. Owing to ground-breaking instruments such as VLT/Sphere or the ALMA telescope array, we now have a first extensive census of disk populations. Moving beyond the core characterisation of relatively isolated disks in the calm Class II stage, the time has come to shift the focus towards the wider context of these systems, that is, the actively star-forming stellar associations, such as the archetypal Taurus, Orion or Lupus regions. Stellar ages of disks with substructure of (likely) planetary origin point to the fact that planet formation is not merely an ubiquitous process, but figuratively speaking happens within the blink of an eye. This mandates to abandon the assumption of the disk as a quiescent entity detached from its surroundings, and instead place it in the context of a collapsing cloud core. Key aspects here are i) the external UV radiation field that can drive powerful photochemical reactions on the surface, ii) perturbations from stellar flybys, iii) gas self-gravity, and iv) magnetic field lines that are self-consistently anchored in the local interstellar medium (ISM); the latter aspect requiring adaptive-mesh technology, provided by the NIRVANA III code, co-developed by the applicant. At the same time, the early appearance of planets poses questions about the solid constituents potentially being inherited from the ISM and “primed” during the protostellar precursor phase. Finally, with the pivotal exchange of angular momentum during the collapse regulated by non-ideal MHD effects, the evolution of microphysical coefficients (i.e., through an ionisation chemistry with recombination on small grains) needs to be followed through the collapse phase, accounting for dust growth by coagulation.

The second data release of the Gaia satellite has revealed much complexity in the structure and kinematics of stars in the Milky Way than previously appreciated. In the disc, Gaia has shown that our Galaxy is still enduring the effects of a collision that set millions of stars moving like ripples on a pond. In the stellar halo, the data uncovered a large single debris structure pointing to a massive accretion event 10 billion years ago, at a time when the disc was in its infancy. Our basic assumptions of dynamical equilibrium and axisymmetry at the basis of nearly all mathematical models of the Galaxy are now falling short to make further progress on our inference on the Galaxy’s formation or the distribution of dark matter. Understanding the detailed time-dependent non-axisymmetric phase-space structure of the Galaxy would open new pathways to understand its detailed accretion history, potentially dating its most major perturbations. This proposal aims to explore the deep coupling between the stellar halo and the Milky Way disc and bulge, to gain new insights on the formation history of the Milky Way through its most major accretion events through a number of state-of-the-art computing techniques. Study 1 will look into studying the formation of the inner-halo through a combination of cosmological genetically modified (constrained) simulations and idealised simulations to constrain the mass and accretion time of the Gaia-Sausage progenitor galaxy (and its potential satellite population which came with it) as well as its impact on the formation of the ``thick disc'' and growth of the Galaxy past z~3-2. Study 2 will look into the impact of known satellites on the dynamical and chemical and age populations’ evolution of the Milky Way using both cosmological/isolated hydrodynamical simulations and idealised numerical N-body simulations, particularly focusing on the role of the Sagittarius dwarf in seeding the perturbations in the disc we see today.