The importance of black hole repositioning for galaxy formation simulations

Bahé, Yannick M.; Schaye, Joop; Schaller, Matthieu; Bower, Richard G.; Borrow, Josh; Chaikin, Evgenii; Kugel, Roi; Nobels, Folkert; Ploeckinger, Sylvia

doi:10.48550/arxiv.2109.01489

Cited by 6 publications

(9 citation statements)

References 106 publications

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“…trees) within Nbody codes are only set up to include gas particles for optimisation reasons. Our results, along with those in Bahé et al (2021), suggest that the black hole occupation fraction of cluster galaxies is severely underestimated within cosmological simulations that employ such repositioning schemes. These results also provide an explanation for the merger-dominated growth of massive supermassive black holes at low redshift.…”

Section: Bcg Black Holesupporting

confidence: 58%

“…Recent works, such as Bahé et al (2021), have noted that there appears to be a lower than expected black hole occupation fraction for cluster galaxies (see their Appendix A). Notably, the model discussed in Bahé et al (2021) also repositions only on gas particles, as typically the neighbour-finding structures (e.g. trees) within Nbody codes are only set up to include gas particles for optimisation reasons.…”

Section: Bcg Black Holementioning

confidence: 96%

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There and back again: understanding the critical properties of backsplash galaxies

Borrow¹,

Vogelsberger²,

O’Neil³

et al. 2022

Preprint

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Backsplash galaxies are galaxies that once resided inside a cluster, and have migrated back oustide as they move towards the apocenter of their orbit. The kinematic properties of these galaxies are well understood, thanks to the significant study of backsplashers in dark matter-only simulations, but their intrinsic properties are not well constrained due to modelling uncertainties in sub-grid physics, ram pressure stripping, dynamical friction, and tidal forces. In this paper, we use the Illustris-TNG-300-1 simulation, with a baryonic resolution of M b ≈ 1.1 × 10 7 M , to study backsplash galaxies around 1302 isolated galaxy clusters with mass 10 13.0 < M 200,mean /M < 10 15.5 . We employ a decision tree classifier to extract features of galaxies that make them likely to be backsplash galaxies, compared to nearby field galaxies, and find that backsplash galaxies have low gas fractions, high mass-to-light ratios, large stellar sizes, and low black hole occupation fractions. We investigate in detail the origins of these large sizes, and hypothesise their origins are linked to the tidal environments in the cluster. We show that the black hole recentering scheme employed in many cosmological simulations leads to the loss of black holes from galaxies accreted into clusters, and suggest improvements to these models. Generally, we find that backsplash galaxies are a useful population to test and understand numerical galaxy formation models.

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Section: Bcg Black Holesupporting

confidence: 58%

Section: Bcg Black Holementioning

confidence: 96%

There and back again: understanding the critical properties of backsplash galaxies

Borrow¹,

Vogelsberger²,

O’Neil³

et al. 2022

Preprint

Self Cite

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show abstract

“…An important concern emerging at this point relates the exact particulars of the BH treatment, which has been shown to have relevant consequences not only on BH properties themselves, but also on other components of the cosmological simulation. For instance, Bahé et al (2021) study the influence of BH repositioning on baryonic components of galaxies. A different work by Ragone-Figueroa et al (2018) found that an improved 'BH pinning' can result in smaller BCG masses, eventually leading to better agreement with observations.…”

Section: Stellar Mass In Bcgsmentioning

confidence: 99%

The Three Hundred project: galaxy cluster mergers and their impact on the stellar component of brightest cluster galaxies

Contreras-Santos,

Knebe,

Pearce

et al. 2022

Preprint

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Using the data set of T T H project, i.e. a suite of 324 hydrodynamical resimulations of cluster-sized haloes, we study galaxy cluster mergers and their effect on colour and luminosity changes of their brightest cluster galaxies (BCG). We track the main progenitor of each halo at 𝑧 = 0 and search for merger situations based on its mass accretion history, defining mergers as very rapid increases in the halo mass. Based upon the evolution of the dynamical state of the cluster we define a pre-and post-merger phase. We create a list of all these events and statistically study their mass ratio and timescales, with the former verifying that all instances are in fact major mergers. By comparing to a control sample of clusters without mergers, we study the effect mergers have on the stellar component of the BCG. Analysing the mass, age and metallicity of the BCG stellar particles, we find that the stellar content of BCGs grows significantly during mergers and, even though the main growth mechanism is the accretion of older stars, there is even a burst in star formation induced by the merger. In our simulations, BCGs in mergers form in median around 70 per cent more stars than those normally growing, although this depends on the radius considered for defining the BCG. Regarding observable properties, we see an increase in SDSS-𝑢 luminosity of 20 per cent during mergers, accompanied by a slightly slower increase of the galaxy 𝑔 − 𝑟 colour as compared to the control sample.

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“…RF18 pointed out that particular care must be taken in controlling the centring of super-massive black hole (SMBH) particles, which leave their host galaxies in the course of the simulations due to frequent dynamical disturbances and mergers, whose effects are probably amplified by numerical limitations. Under these circumstances, the SMBH energy feedback does not effectively suppress gas over-cooling (Borgani et al 2006;Wurster & Thacker 2013) nor star formation in the centre of massive galaxies (Ludlow et al 2020;Bahé et al 2021). Thus it is worth studying the impact of feedback schemes, softening and resolution in producing the M SH − V max relation.…”

Section: Introductionmentioning

confidence: 99%

“…We report data for 10xB20 simulations (black solid line), 1xR15 simulations subset of 10xB20 regions (solid cyan line), 1xRF18 simulations subset of 10xB20 regions (pink line) and 1xf SH (magenta line), for SHs with projected distances < 0.15R vir (right panel). We compare our high-resolution simulations with simulated data points of high-resolution Hydrangea simulations(Bahé et al 2021) (red).…”

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confidence: 99%

Galaxies in the central regions of simulated galaxy clusters

Ragagnin,

Meneghetti,

Bassini

et al. 2022

Preprint

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Context. Meneghetti et al. (2020) (hereafter M20) found that observed cluster member galaxies are more compact than their counterparts in ΛCDM hydrodynamic simulations, as indicated by the difference in their strong gravitational lensing properties. M20 reported that the measured and simulated galaxy-galaxy strong lensing events on small scales are discrepant by one order of magnitude. Among possible explanations for this discrepancy, some studies suggested that simulations with better resolution and implementing different schemes for galaxy formation, compared to the ones used in M20, could bring simulations in better agreement with the observations. Aims. In this paper, we assess the impact of numerical resolution and of the implementation of energy input from AGN feedback models on the inner structure of cluster sub-haloes in hydrodynamic simulations. Methods. We compare several zoom-in re-simulations of a sub-sample of the cluster-sized haloes studied in M20, obtained by varying mass resolution, softening length and AGN energy feedback scheme. We study the impact of these different setups on the subhalo (SH) abundances, their radial distribution, their density and mass profiles and the relation between the maximum circular velocity, which is a proxy for SH compactness. Results. Regardless of the adopted numerical resolution and feedback model, SHs with masses M SH 10 11 h −1 M , the most relevant mass-range for galaxy-galaxy strong lensing, have maximum circular velocities ∼ 30% smaller than those measured from strong lensing observations of Bergamini et al. (2019). We also find that simulations with less effective AGN energy feedback produce massive SHs (M SH 10 11 h −1 M ) with higher maximum circular velocity and that their V max − M SH relation approaches the observed one. However the stellar-mass number count of these objects exceeds the one found in observations and we find that the compactness of these simulated SHs is the result of an extremely over-efficient star formation in their cores, also leading to larger-than-observed SH stellar mass. Conclusions. Regardless of the resolution and galaxy formation model adopted, simulations are unable to simultaneously reproduce the observed stellar masses and compactness (or maximum circular velocities) of cluster galaxies. Thus, the discrepancy between theory and observations that emerged from the analysis of M20 persists. It remains an open question as to whether such a discrepancy reflects limitations of the current implementation of galaxy formation models or the ΛCDM paradigm.

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The importance of black hole repositioning for galaxy formation simulations

Cited by 6 publications

References 106 publications

There and back again: understanding the critical properties of backsplash galaxies

There and back again: understanding the critical properties of backsplash galaxies

The Three Hundred project: galaxy cluster mergers and their impact on the stellar component of brightest cluster galaxies

Galaxies in the central regions of simulated galaxy clusters

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