Scaling relations for MATLAS dwarfs and luminous subhaloes in the TNG50 simulation. Left: selection criteria for MATLAS-like dwarfs mock-observed in TNG50. The blue line indicates the linear cut between regular galaxies and dwarfs adopted in MATLAS (Habas et al. 2020). The green, red, and black lines respectively represent cuts on average surface brightness ⟨μ_g⟩, apparent magnitude m_g, and apparent effective radius motivated by the distribution of the MATLAS dwarfs (see upper panel). The observed dwarfs demonstrate photometric properties consistent with their TNG counterparts, except for a population at larger m_g than expected in the simulated ⟨μ_g⟩−m_g relation. This discrepancy can be explained by assuming that a fraction of the MATLAS dwarfs are background galaxies with distances up to 100 Mpc. Right: physical properties of luminous subhalos in TNG’s mock-observed fields. MATLAS-like dwarfs that satisfy the selection criteria are indicated as white circles. Distances are not available for around 85% of the MATLAS dwarfs, and they are assumed to lie at the same distance as their field’s target host galaxy. The TNG dwarfs, when making this assumption, also follow a similar extended distribution in R_e − M_g space. MATLAS dwarfs with known distances follow the true TNG distribution more closely.