arXiv subjects

Bruno M. Celiz

Publications and source records attributed to Bruno M. Celiz.

4 recordsLinked to original sources

arXiv2026

The origin of the stellar mass-size relation of satellite galaxies in the COLIBRE simulations

We study the stellar mass-size relation of satellite galaxies in the COLIBRE suite of cosmological hydrodynamical simulations. Satellites deviate from the relation that holds for centrals galaxies, where at the high mass end, $\log (M_*/{\rm M}_\odot) > 10.5$, sizes (defined as the 3D half-mass radius $r_{\rm h,*}$) increase systematically with mass ($r_{\rm h,*} \propto M_*^{0.5}$), whereas at lower masses, $8 < \log(M_*/{\rm M}_\odot) < 10.5$, the relation flattens and galaxy size becomes, on average, almost independent of mass ($r_{\rm h,*} \approx 3$ kpc). At $z=0$, dwarf satellites (defined as those with $8 < \log(M_*/{\rm M}_\odot) < 9$) are systematically larger than centrals of similar $M_*$. This trend reverses for bright satellites ($9 < \log(M_*/{\rm M}_\odot) < 10.5$), which are typically smaller than centrals of similar mass. We trace these trends to evolutionary processes affecting satellites after infall into the haloes of more massive hosts. At infall, dwarf satellites are typically gas-rich, dark matter-dominated systems with relatively large baryon-induced cores. These satellites quench rapidly after losing their gas to ram pressure, which prompts an immediate impulsive expansion due to the shallowing central potential, followed by secular expansion as their cored dark matter haloes are gradually stripped by tides. In contrast, the inner regions of bright satellites are baryon-dominated and resilient to tides. Centrally concentrated star formation increases their stellar mass, leading to smaller sizes and higher stellar metallicities (by $\approx 0.2$ dex) than those of centrals of similar mass. These distinct satellite evolutionary pathways lead to identifiable features in the mass-size-metallicity relations that may be compared with observations.

astro-ph.GA↗

arXiv2026

Mass-morphology relation of TNG50 galaxies

We used the cosmological hydrodynamical simulation TNG50 to study the galaxy mass-morphology relation, as measured by the rotational support of the stellar component of simulated galaxies. For isolated galaxies with a stellar mass in the range of $8<\log(\mathit{M_{*}/M_{\odot}}) < 11$, rotational support increases with $\mathit{M_*}$, from dispersion-supported spheroidal dwarfs to massive galaxies with prominent, rotationally supported discs. Our results indicate that this correlation arises from the spatial distribution of star formation in TNG50 galaxies, which occurs primarily in two distinct regions: an unresolved, non-rotating central baryonic clump $(r \lesssim 1~\mathrm{kpc})$ and a rotationally supported outer disc, separated by a quiescent region. This explains why dwarfs have less rotational support than massive galaxies and why all dwarfs have similar stellar half-mass radii, regardless of $\mathit{M_*}$. It also explains why massive galaxies in TNG50 appear to form inside-out (as the outer disc grows), whereas dwarfs form outside-in, as star formation in the dominant inner clump moves progressively inward. The clump-disc segregation of star formation in TNG50 galaxies is probably numerical in origin. Inner clumps are formed by the accumulation of low-angular-momentum gas supported by the equation of state introduced to prevent artificial fragmentation. The decoupled-wind feedback implementation in TNG50 helps to preserve the clumps, but disrupts disc formation in its immediate surroundings. This hinders the formation of discs in (dwarf) galaxies whose sizes are not substantially larger than the clump, but it has little effect on the larger discs of more massive systems. Our results argue in favour of taking caution when interpreting the dependence on stellar mass of TNG50 galaxy morphologies, or the evolution of galaxy sizes, especially at the dwarf end.

astro-ph.GA↗

arXiv2025

Accreted stars and stellar haloes of simulated galaxies in TNG50

We use the TNG50 cosmological hydrodynamic simulation to study the accreted stellar component and stellar haloes of isolated galaxies spanning a wide range of masses ($10^8<M_*/M_\odot<10^{11}$). We find that stars formed in the main progenitor (i.e., in-situ stars) typically dominate the inner regions as far as $\sim$10 half-light radii from the centre, implying that detecting uncontrovertible evidence for the presence of an accreted stellar halo requires probing the far outskirts of a galaxy. Stars from accreted, disrupted satellites (i.e., ex-situ stars) dominate beyond that radius (roughly $25\%$ of the virial radius, $r_{200}$), which we identify as the inner boundary of the outer stellar halo. The fraction of accreted stars decreases monotonically with decreasing galaxy mass, $M_*$, from $\sim$$20\%$ on average in $\sim$$2\times 10^{12}\, M_\odot$ haloes ($M_*\sim$$10^{11}\, M_\odot$) to $2$-$3\%$ in $\sim$$2\times 10^{10}\, M_\odot$ haloes ($M_*\sim$$10^{8}\, M_\odot$). The outer halo has a mass comparable to roughly $10\%$ of all accreted stars. Fewer than $\sim$$30\%$ of stars in the outer halo are in-situ stars, many of which originate from star-forming satellites during the late stages of disruption, especially in low-mass systems. Accreted stars are systematically more metal poor in less massive systems, which makes the outer haloes of dwarf galaxies a fertile hunting ground for extremely metal-poor stars. At given galaxy mass, the more massive stellar haloes are systematically more concentrated (smaller $R_{\rm eff}$) and have steeper density profiles (larger $n$). Our results provide a blueprint for interpreting observations of the outskirts of isolated galaxies in terms of their assembly histories.

astro-ph.GA↗

arXiv2025

Compact groups of galaxies in the TNG100 simulation

Using the TNG100 cosmological simulation, we study the formation and evolution of compact groups of galaxies. Over a redshift range of $0 \lesssim z \lesssim 0.2$, we identify these compact groups as FoF galaxy groups with high mean surface brightness ($\overlineμ_r < 26.33 ~ \mathrm{mag~arcsec^{-2}}$) and a minimum of 4 galaxy members. Typically, our compact groups have a median characteristic size of $\sim$$150$ kpc, 1D velocity dispersions of $150 ~ {\rm km ~ s^{-1}}$, and stellar masses around $2\times 10^{11} ~ M_{\odot}$. Roughly 1\% of galaxies of stellar mass above $10^9 ~ M_{\odot}$ lie in physically dense compact groups. We found that these systems do not constitute a separate category within the broader population of galaxy groups; instead, they represent the lower end of the size distribution in the sequence of galaxy group sizes. We traced their evolution backward in time, revealing that they initially form as galaxies systems with a mean low surface brightness that systematically increases to a peak value before stabilizing over time, exhibiting oscillatory behaviour over the following several Gyrs during which mergers may occur. Mergers often transform compact groups with typically four members into galaxy pairs or triplets, which may eventually can increase again their number of members accreting a new galaxy. Nevertheless, the full merging of all constituent galaxies into a single massive galaxy is a rare phenomenon.

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