Marseille conference


This week I will be at the University of Aix-Provence, for a conference focussed on intergalactic medium. I will be discussing gas flows around galaxies, and highlighting the work of my student Jon Davies, who is researching the origin of diffuse X-ray emission from the circumgalactic medium.

Heidelberg workshop

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This week I am at the Internationale Wissenschaftsforum der Universität Heidelberg (IWH), to participate in a workshop concerned with the influence of star formation and feedback from the scale of molecular clouds up to the galaxy population. I’ll be giving an invited talk on our recent work on the impact of a variable IMF in cosmological simulations. The meeting will also focus heavily on the E-MOSAICS project led here at LJMU.

First self-consistent cosmological simulations with a variable IMF

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Chris Barber, Joop Schaye (both Leiden Observatory) and I have recently posted the first two papers from a series investigating the influence of a variable initial mass function on the properties of the galaxy population. We use two IMF variations – one top-heavy (more remnants with respect to a normal IMF) and one bottom-heavy (more dwarf stars) – which are calibrated to reproduce the mass-to-light ratio excess inferred in the centres of massive galaxies from dynamical and stellar population modelling. The first paper details our methodology and calibration techniques, whilst the second explores the influence on the galaxy population. A third paper, due soon, investigates radial variations within galaxies due to the variable IMF.

Reconstructing the Milky Way’s assembly history with globular clusters

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Today the E-MOSAICS team posted to the arXiv a paper [download here] demonstrating that it is possible to infer key aspects of the formation and assembly history of our own Milky Way, by analysing the age and heavy element enrichment properties of globular clusters. Our study suggests that the Milky Way is unusual when compared to galaxies of similar mass – it seems to have formed unusually early in cosmic history (a result also I also inferred with my student Ted Mackereth from analysis of the enrichment properties of disc stars – see here). We were also able to infer the properties of three satellite galaxies that merged with the Milky Way in the distant past, associating two with known relics. The third appears to have been the most massive satellite to merge with the Milky Way, likely in the interval z = 0.6-1.3. Finding a relic of this galaxy presents an exciting challenge to observational studies of our Galaxy.

ESA press release for CGM-MASS team


Today the European Space Agency (ESA) issued a press release (here) discussing results from our recent paper, in which we use the XMM-Newton X-ray observatory to measure the mass of hot, X-ray emitting gas surrounding local galaxies. The paper has important implications for the search for the “normal” matter in the Universe!

Diverse alpha-enhancement in galaxy discs

Today we posted to the arXiv a new paper, in which we use EAGLE to examine the origin of spreads (or even bimodality) in the alpha-element abundances of disc stars, as is observed in the Milky Way. We conclude that such abundance patterns are uncommon, implying that in this respect the Milky Way is not representative of similarly-massive disc galaxies. The simulations indicate that the unusual abundances are likely a consequence of the Milky Way’s dark matter halo having formed quickly, early on cosmic history.

RS Fellows Enhancement Award


I’m grateful to the Royal Society for today awarding me an “Enhancement Award” to supplement my University Research Fellowship. This funding will be used to upgrade the ARI’s high performance computing facility with high performance interconnect, dramatically increasing the flexibility of the machine and enabling further development of simulations for the E-MOSAICS, ECO and BAHAMAS suites that are led by the computational galaxy formation group.

Science Museum Lates exhibition

Yesterday, my colleague Jim Geach and I had the privilege to present our research to the public at the Science Museum in London, as part of their “Lates” themed evenings. This was a particularly special Lates event, as its purpose was to launch the Tomorrow’s World online platform, a collaboration between the Science Museum, the BBC, the Royal Society and the Wellcome Trust. The event attracted nearly 5000 members of the public, many of whom visited our exhibition to see visualisations of numerical models of galaxy evolution, and discuss our science with us. The move we presented is available to view here.