Liverpool John Moores University ARI Consolidated Grant 2021-2024

We will carry out work at the forefront of astrophysics using both observations and theory. The ARI's mission is to be a world-leading research centre at the highest international level of excellence. Our research uses the most advanced facilities and data analysis techniques. The projects in this case are technically demanding and require PDRA and other support to aid the delivery of the science.

Building on ARI's world-leading expertise in star formation (SF), we will investigate the connection between SF and gas physics in the Milky Way by mapping the SF efficiency in 3-D and studying the connection between SF and the gas distribution in the Galaxy. A second project will look at SF processes in different environments, and particularly in the conditions prevailing in the early Universe, to assess the survival probabilities of planetary systems as a function of environment and cosmological epoch.

We will determine how massive stars appear just before they die, by incorporating realistic mass-loss rates into calculations of their late-stage evolution, and building winds into the model atmospheres used to study these final phases.

We will address a major unsolved problem, the formation mechanism of globular clusters, using the recent discovery of multiple stellar populations in these systems (driven largely from ARI) to give a new perspective on this question. Globular clusters will also be used in a separate study to shed light on the evolution of their host galaxies, using a unique combination of detailed cluster formation physics embedded in world-leading cosmological simulations.

Through a joint analysis of major surveys of Milky Way (MW) stars (APOGEE, Gaia-WEAVE) and cosmological numerical simulations (EAGLE), we will address the contribution of satellite galaxies and in situ SF to the mass to the MW halo, and hence shed new light on the question of whether the MW is a typical galaxy.

Two of the proposed projects address cosmological questions. The first is a study of the long-lasting problem of the cosmological lithium abundance, which will be tackled through spectroscopic analysis of a large sample of metal-poor lower red giant branch stars. The second will look at the impact of massive neutrinos on cosmological structure formation, using a novel and highly efficient method based on non-linear cosmological perturbation theory.

Time-domain astrophysics has always been a core area of ARI research, underpinned by the world-leading 2-metre robotic Liverpool Telescope (LT). This application represents a broadening of this activity, encompassing compact object mergers and the full range of stellar explosions, from novae to GRBs. The one theoretical proposal in this area concerns modelling of nova super-remnants, motivated by the discovery of such a remnant in M31 by ARI researchers.

This work has implications for nova population studies and pathways to SNIa events. We will compute the observable characteristics of supernova explosion models ofstars with different masses, degrees of stripping and explosion energies, and compare the outcomes with observations. We will also develop and exploit the first large, uniformly-selected, spectroscopically-complete sample of optical transients using the Zwicky Transient Facility.

This will allow us to study the observational parameter space of all forms of stellar death and prepare for LSST.

A follow-up programme studying counterparts to gravitational wave events will provide a unique insight into the mergers of compact objects, combining observational studies with the development of new models for the characterisation of these events. These activities capitalise on ARI's expertise in this field and exploit our privileged access to the SN detection survey ZTF; LIGO-Virgo EM follow-up experiments, the Swift GRB satellite and observations on a range of leading astronomical facilities including the LT.