The COLIBRE project: cosmological hydrodynamical simulations of galaxy formation and evolution

Abstract

We present the COLIBRE galaxy formation model and the COLIBRE suite of cosmological hydrodynamical simulations. COLIBRE includes new models for radiative cooling, dust grains, star formation, stellar mass loss, turbulent diffusion, pre-supernova stellar feedback, supernova feedback, supermassive black holes and active galactic nucleus (AGN) feedback. The multiphase interstellar medium is explicitly modelled without a pressure floor. Hydrogen and helium are tracked in non-equilibrium, with their contributions to the free electron density included in metal-line cooling calculations. The chemical network is coupled to a dust model that tracks three grain species and two grain sizes. In addition to the fiducial thermally-driven AGN feedback, a subset of simulations uses black hole spin-dependent hybrid jet/thermal AGN feedback. To suppress spurious transfer of energy from dark matter to stars, dark matter is supersampled by a factor 4, yielding similar dark matter and baryonic particle masses. The subgrid feedback model is calibrated to match the observed $z \approx 0$ galaxy stellar mass function, galaxy sizes, and black hole masses in massive galaxies. The COLIBRE suite includes three resolutions, with particle masses of $\sim 10^5$, $10^6$, and $10^7\,\text{M}_\odot$ in cubic volumes of up to 100, 200, and 400 cMpc on a side, respectively. The largest runs use 136 billion ($5 \times 3008^3$) particles. We describe the model, assess its strengths and limitations, and present both visual impressions and quantitative results. Comparisons with various low-redshift galaxy observations generally show very good numerical convergence and excellent agreement with the data.

Figures (32)

• Figure 1: The five cubic COLIBRE boxes, which have side lengths ranging from 25 to 400 comoving Mpc. Colour shows total surface density (in 5 Mpc thick faces) at $z=0$. The volumes available at high (m5), intermediate (m6), and low (m7) resolution are indicated. Note, however, that at the time of writing the 50 and 100 Mpc high-resolution simulations have not yet reached redshift $z=0$.
• Figure 2: The evolution of the cosmic rate of SNIa per unit time and comoving volume for the fiducial (solid) and hybrid AGN feedback (dashed) simulations of different resolutions (different colours). The data points correspond to observed rates at $z<0.2$Cappellaro1999Hardin2000Madgwick2003Strolger2003Blanc2004Mannucci2005Horesh2008Dilday2010Li2011Quimby2012Frohmaier2019, $0.2<z<0.75$Pain2002Barris2006Neill2006Botticella2008Melinder2012Cappellaro2015 and at $z>0.75$Tonry2003Dahlen2004Dahlen2008Poznanski2007Kuznetsova2008Rodney2010Graur2011Perrett2012Okumura2014Rodney2014. All simulations are in reasonable agreement with the compilation of observations.
• Figure 3: Visual impression of the dynamic range in the high-resolution COLIBRE simulation L025m5 at $z=0.1$. The top left panel shows a projection of the entire simulation with the colour encoding baryon surface density. The other panels zoom into different regions and show the stellar light in HST colours accounting for attenuation by dust. The top right and middle right panels zoom into 800 pkpc cubic regions of groups of mass $M_\text{200c} = 10^{13.4}\,\text{M}_\odot$ and $10^{13.3}\,\text{M}_\odot$, respectively. The insets in these two panels show 75 pkpc $\times$ 75 pkpc and 30 pkpc $\times$ 30 pkpc zoom-in images of galaxies with stellar mass $M_* = 10^{11.3}\,\text{M}_\odot$ and $10^{10.1}\,\text{M}_\odot$, respectively. The orientations of these two galaxies are the same as in the other images of the same regions. The two bottom rows show face- and edge-on views of four galaxies with stellar masses in the range $10^{10.8} \le M_*/\text{M}_\odot \le 10^{11.3}$. These galaxies are numbered and their locations are indicated in the top left or middle right panels. Galaxy zooms show regions of 75 pkpc $\times$ 75 pkpc for face-on orientations and 75 pkpc $\times$ 30 pkpc for edge-on orientations, except for the zoom of galaxy 1 on the bottom left, which is 50 pkpc $\times$ 50 pkpc and 50 pkpc $\times$ 20 pkpc for the face- and edge-on orientations, respectively. COLIBRE simultaneously models the large-scale cosmic web and the internal structure of galaxies.
• Figure 4: Face-on (top) and edge-on (bottom) view of a $z=0$ disc galaxy of mass $M_* = 8\times 10^{10}\,\text{M}_\odot$ and $\text{SFR} = 2.7~\text{M}_\odot\,\text{yr}^{-1}$ in the L025m5 simulation. From left to right the columns show stellar light, Hi column density, H$_2$ column density times 2, and dust surface density. The image sizes are 75 kpc $\times$ 75 kpc for face-on and 75 kpc $\times$ 30 kpc for edge-on orientations. Beyond the gas-poor centre, molecular hydrogen is more concentrated towards the centre and in the spiral arms than atomic hydrogen, while the dust distribution is intermediate between that of atomic and molecular hydrogen (compare, for example, the green in the H$_2$ map with the red in the dust map).
• Figure 5: Comparison of galaxy morphologies across different COLIBRE resolutions. Each column shows face-on and edge-on images of the same galaxy in the L025m5 (top), L025m6 (middle), and L025m7 (bottom) simulations at $z=0$. The different columns show different galaxies with stellar mass increasing from left to right. The stellar masses for m6 resolution are indicated above each column. These can differ by $\pm 0.1$ dex for the other resolutions. The images show stellar light in HST colours and account for attenuation by dust. They are 50 kpc across except for the last column, which is 75 kpc across. Higher-resolution simulations reveal more detail and predict thinner discs. Except for the lowest mass galaxy, the galaxy shape can be inferred at all resolutions.