The tidal evolution of satellite galaxies in cosmological simulations: insights from COLIBRE

Abstract

We investigate the co-evolution of the stellar and dark matter mass of satellite galaxies using the COLIBRE cosmological hydrodynamical simulations with subhaloes resolved by the history-based HBT-HERONS subhalo finder. We identify a universal tidal track connecting stellar mass loss to subhalo mass loss characterized by two distinct phases, which can be well described by the two-parameter model. The initial phase consists primarily of dark matter stripping, whereas stellar stripping becomes significant only after the subhalo bound mass fraction drops below a critical value ($\sim 0.057$). We find a bimodal mass loss rate distribution of subhaloes. In satellites with modest mass loss rates, the stellar mass is largely frozen. By contrast, the galaxy quickly becomes unresolved, along with the dark matter component for the extreme-mass-loss population, naturally explaining the lack of ``orphan'' galaxies in previous hydrodynamical simulations. Our model also predicts the formation condition for dark-matter-deficient galaxies (DMDGs), whose abundance peaks at $m_{*}\sim 10^{9.5}\,\rm{M}_{\odot}$. The abundance of DMDGs can be very sensitive to numerical effects, with COLIBRE resolving a much larger DMDG population than previous hydrodynamical simulations. We also estimate the influence of artificial disruption on the satellite stellar mass function, which can amount to 20 (50) per cent at $m_* \sim 10^{9} (10^{8}) \, \rm M_\odot$, given a baryonic mass resolution of $\sim 10^{6}\,\rm{M}_{\odot}$.

Figures (18)

• Figure 1: The mass and orbit evolution of example satellite subhaloes after reaching their peak mass $m_{\rm sub,peak}$. The left column shows the mass evolution. Different colours represent the mass evolution of different components, while the black line indicates the total bound mass of the subhalo. The grey vertical dotted line marks the accretion time $t_{\rm{acc}}$, defined as the time when the subhalo falls into the host halo. The upper two rows show resolved satellites that survive at $z=0$. The lower two rows show lost satellites; the DM mass resolution is indicated by the grey horizontal dashed line. The middle column shows the evolution of the distance to the host halo. The grey dashed line in this column shows the growth of the $R_{\rm vir}$ of the host halo for reference. The right column shows satellite orbit projection on the X-Y panel. The trajectory starts from the black dot and ends at the red cross, with the evolution time colour-coded. The centre of the host halo is presented by the black cross. The $R_{\rm vir}$ of the host halo at $t_{\rm start}$ ($t_{\rm{end}}$) is shown by a grey(red) dashed circle for reference.
• Figure 2: The stellar evolutionary (from right to left) tidal tracks of satellite galaxies in clusters with $M_{\rm host}>10^{14}\rm{M}_{\odot}$ from colibre L200m6. The solid line indicates the median distribution of tidal tracks, with the shaded region representing the 16th–84th percentile distribution. Blue and red colours correspond to resolved and lost subhalo populations, respectively. The black dashed line shows the tidal track given by Smith2016.
• Figure 3: Joint and marginal distributions of the tidal track parameters $f_{\rm d}$ and $b$ for satellites in the L200m6 simulation. The sample is restricted to systems with a peak stellar mass $m_{\rm *,peak} > 10^{8}\,\rm{M}_{\odot}$ and a minimum remaining stellar mass fraction $f_{*, \rm min} < 0.5$. In the top and right sub-panels, the blue stepped histograms represent the probability density functions of $f_{\rm d}$ and $b$, respectively. The solid black curves denote the corresponding best-fitting log-normal distributions. Physically, a lower $f_{\rm d}$ value indicates a more delayed onset of stellar stripping relative to the DM. A lower $b$ value reflects a lower stellar stripping efficiency, characteristic of a more tightly bound and resilient stellar structure. The red dashed vertical and horizontal lines show the parameters found by Smith2016 for reference.
• Figure 4: Comparison between the raw simulation data and the extrapolated tidal stripping model for satellite galaxies in cluster-scale haloes ($M_{\rm{host}} > 10^{14}\,\rm{M}_{\odot}$). All selected satellites have $m_{\rm{sub,peak}} > 10^{10}\,\rm{M}_{\odot}$. In all panels, thick solid lines and shaded regions represent the median and 16th–84th percentile ranges, while thin lines show the trajectories of 100 randomly selected individual systems. Blue and red colours denote the resolved and lost populations, respectively. Top-left: Subhalo mass fraction ($f_{\rm sub}$) measured directly from the simulation. Top-right: The same subhalo sample, but with the mass loss of the lost population reconstructed using our exponential extrapolation model (Eq. \ref{['eq:masslossrate']}$\&$\ref{['eq:extra']}). Bottom-left: Stellar mass fraction ($f_*$) measured directly from the simulation. Many lost satellites still possess significant stellar components at the moment of being lost. Bottom-right: Predicted stellar mass evolution using the universal tidal track (Eq. \ref{['eq:He26']}) applied to the extrapolated subhalo mass.
• Figure 5: The distribution of subhalo mass loss and rates.