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Latin American Chinese European Galaxy Formation Network

Periodic Reporting for period 1 - LACEGAL (Latin American Chinese European Galaxy Formation Network)

Reporting period: 2017-03-01 to 2019-02-28

Spectacular breakthroughs in astronomy have been driven by a combination of observational advances and groundbreaking computer simulations. Simulations are now accepted as being essential for the interpretation and exploitation of data. Europe is a world leader in this area. The aim of this RISE project is to build on the highly successful FP7 LACEGAL IRSES to avoid fragmentation of expertise and concentration of supercomputer resources in a few groups. Our research program addresses key questions in galaxy formation and the large-scale structure of the Universe and is divided into 4 scientific work packages, covering different scales and physical processes: 1) Simulations of Milky-Way like galaxies 2) Simulations of the galaxy population 3) Dark matter physics 4) Large-scale structure of the universe/Cosmology.

This is important for society because astronomy has long held an interest for the general public and brings science to new audiences. The scientific focus of this RISE project is computer simulation of the formation of cosmic structures. These provide visually striking media that we have used to engage people at various outreach events. A further benefit for society is the training of early stage researchers in high performance computing and data science; computational cosmology and astronomy are challenging scientific problems that develop computing and analysis skills that are readily transferable outside academia.

The overall objectives of the LACEGAL RISE are to 1) avoid fragmentation of expertise across Europe 2) to build a new state-of-the-art in the simulation of cosmic structures from dwarf galaxies, through Milky Way analogues to the largest structures in the Universe 3) to build new research collaborations between leading European research centres and third countries.
Our research program has been underpinned by a vigorous series of secondments. Almost 43 researchers have undertaken secondments for a period of 124 months (note that some of these are underway and extend beyond the end of this reporting period). The results of the project have been disseminated in 21 papers submitted for publication in peer reviewed journals, all of which are available on the open access preprint server arXiv and in two conferences which received significant support from LACEGAL.

The main results so far are:

• An explanation of the origin of the observed decline in [O/Fe] (and [Mg/Fe]) with Galactocentric distance for high-metallicity stars ([Fe/H] > -1.1) based on a sample of halo stars selected within the Apache Point Observatory Galactic Evolution Experiment (APOGEE) fourteenth data release (DR14).

• The use of the state-of-the-art EAGLE simulation to study the oxygen abundance gradients of gas discs in galaxies at z = 0.

• The study of the evolution of assembly bias using a semi-analytical model of galaxy formation implemented in the Millennium-WMAP7 N-body simulation.

•The study of cosmic voids in the normal-branch Dvali-Gabadadze-Porrati (nDGP) braneworld models that are representative of a class of modified gravity theories where deviations from General Relativity are usually hidden by the Vainshtein screening in high-density environments.
To date 43 researchers have benefited from the LACEGAL RISE secondments, gaining training in high performance computing and data analysis techniques. The research projects carried out during these secondments have led to progress beyond the current state-of-the-art: 1) the generation of galaxy catalogues from cosmological N-body simulations of standard and modified gravity models. 2) the establishment of the role of the environment in shaping galaxy properties. 3) the public release of a code to model the propagation of Lyman-alpha photons through the interstellar and intergalactic medium 4) the proposal of a new explanation for the magnitude of the cosmological constant 5) the elucidation of the physical process that shape the galaxy population.