Silvio Rodriguez | Searcharxiv

arXiv2026

The connection between surface brightness and satellite systems for central galaxies through Illustris TNG

We analyse different properties of central low-surface-brightness galaxies (LSBGs) and their satellite systems using the simulation Illustris TNG-100, in order to deepen our understanding of the formation mechanism of LSBGs in a $\Lambda$CDM cosmology. We find differences in the spin and the concentrations of the LSBGs haloes and the host haloes of high-surface-brightness galaxies (HSBGs), consistent with previous studies. By analysing their spatial and kinematical distribution of satellites, we find that LSBGs tend to have a larger number of satellites than HSBGs and with a larger velocity dispersion. Moreover, we obtain a continuous relation between the number of satellites and surface brightness, particularly for massive central galaxies. We also find a relation between surface brightness and the relative tangential velocity of the satellites. For a given stellar mass, the existence of LSBGs is strongly correlated with their satellite system dominated by rotation. Furthermore, the satellite system is systematically in counter-rotation with respect to the primary disc in LSBGs. We propose that this fact reflects that these galaxies have not experienced a significantly high rate of mergers, which are more likely associated with radial orbits expected in systems of galaxies with a high surface brightness.

astro-ph.GA↗

arXiv2024

The assembly of the most rotationally supported disc galaxies in the TNG100 simulations

Disc dominated galaxies can be difficult to accommodate in a hierarchical formation scenario like $\Lambda$CDM, where mergers are an important growth mechanism. However, observational evidence indicates that these galaxies are common. We seek to characterise the conditions that lead to the formation of disc dominated galaxies within $\Lambda$CDM. We use dynamical decomposition in all galaxies with stellar mass $M_*=[10^{10} \rm - 10^{11}]\; \rm M_\odot$ within the simulation Illustris TNG100. We select a sample of 43 mostly-disc galaxies having less than $\sim 10\%$ of their mass into a bulge component. For comparison, we also study two additional stellar-mass matched samples: 43 intermediate galaxies having $\sim 30\%$ of their mass in the bulge and 43 with purely spheroidal-like morphology. We find that the selection based on stellar dynamics is able to reproduce the expected stellar population trends of different morphologies, with higher star-formation rates and younger stars in disc-dominated galaxies. Halo spin seems to play no role in the morphology of the galaxies. At fixed $M_*$, our mostly-disc and intermediate samples form in dark matter haloes that are $2$-$10$ times less massive than the spheroidal sample, highlighting a higher efficiency in disc galaxies to retain and condensate their baryons. On average, mergers are less prevalent in the build up of discs than in spheroidal galaxies, but there is a large scatter, including the existence of mostly-disc galaxies with $15\%$-$30\%$ of their stars from accreted origin. Discs start forming early on, settling their low vertical velocity dispersion as early as $9$-$10$ Gyr ago, although the dominance of the disc over the spheroid gets established more recently ($3$-$4$ Gyr ago). The most rotationally supported discs form in haloes with the lowest mass in the sample and best aligned distribution of angular momentum in the gas.

astro-ph.GA↗