The project contains a mixture of technical developments and scientific applications. On the technical side:
1. We have made enormous progress in the development of the SWIFT cosmological simulations code. In
collaboration with colleagues at Leiden, we have nearly completed the implementation of new ``subgrid'' physics
models that make it possible to simulate the small-scale processes that are vital for this project.
2. We had a successful test flight of SuperBIT.
3. The design, construction and deployment of the DESI survey instrumentat the Mayall telescope in Arizona were
all successfully completed in budget and on time.
We have published 73 refereed papers since the start of the project, including an extensive review of dark matter subhaloes
(Zavala and Frenk 2019) and a paper in Nature (Wang et al 2020). These papers have already been cited over 1200 times,
with 16 of them having accrued over 30, and 6 over 50, citations each since publication in 2019.
Highlights include:
1. The completion of the Auriga high-resolution simulations of Milky Way-like galaxies (Grand et al. 2018). These
represent the state-of-the art in the subject and have been used for a variety of studies of the satellites (Bose et
al. 2019, Simpson et al. 2019) and stellar halo (Monachesi et al. 2019, Fattahi et al. 2019, 2020) of the Milky Way. They are
the basis of the AuriGaia stellar mock catalogues of the GAIA DR2 data (Grand et al. 2018), which we have publicly released.
2. The most accurate determination of the mass of the Milky Way to date from a combination of satellite dynamics
using GAIA data and the Auriga simulations (Callingham et al. 2019) and, by fitting physically motivated models to the
Gaia DR2 Galactic rotation curve and other data, of its spatial distribution (Cautun et al. 2020).
3. A detailed analysis, based on a systematic set of targeted cosmological hydrodynamics simulations, of the mechanisms that can
create cores in the centres of cold dark matter haloes by baryonic effects (Benitez-Llambay et al 2019, Bose et al. 2019).
4. An analysis of the neutral hydrogen rotation curves of simulated dwarf galaxies applying the same techniques as for observational data.
The ``diversity of rotation curves'' (which we uncovered in earlier work) does not imply the presence of central cores but,
instead, could be due to non-circular velocities in the gas (Oman et al. 2019, Santos-Santos et al. 2020).
5. A variety of studies relevant to dark matter detection, from the properties of decaying dark matter (Lovell et al. 2019a, 2019b)
through the effects of the galactic disc on the velocity distribution of cold dark matter particles (Bozorgnia et al. 2019a, 2019b) to the
destruction of small subhaloes as they pass through the galactic disc (Richings et al. 2020).
6. Studies of the dynamics and spatial distribution of galactic satellites, including their peculiar arrangement in a
rotating plane of satellites (Riley et al 2019, Callingham et al. 2020, Cautun et al. 2020, Shao et al. 2019, 2020).
7. A dark matter simulation that achieves a dynamic range of 30 orders of magnitude in mass and resolves the internal structure
of Earth-mass haloes. Halo density profiles are universal over the entire mass range and are well described by the Navarro-Frenk-White
formula. Halo mass and concentration are tightly related in a way that depends on cosmology and on the nature
of the dark matter. Small halos contribute about equally (per logarithmic interval) to the dark matter annihilation luminosity,
which we find to be smaller than all previous estimates by factors ranging up to one thousand (Wang et al. 2020).
8. A physical model of the formation of the first galaxies and the prediction that dark matter halos with present-day mass less than 3x10^8 Mo
are all dark, while those with mass above 5×10^9 Mo are all luminous. The results of the model are in excellent agreement with cosmological
hydrodynamic simulations (Benitez-Llambay and Frenk 2020).
