Black hole mass of central galaxies and cluster mass correlation in cosmological hydro-dynamical simulations

Abstract

Context. The correlations between the properties of the brightest cluster galaxy (BCG) and the mass of its central super-massive black hole (SMBH) have been extensively studied from a theoretical and observational angle. More recently, relations connecting the SMBH mass and global properties of the hosting cluster, such as temperature and mass, were observed. Aims. We investigate the correlation between SMBH mass and cluster mass and temperature, their establishment and evolution. We compare their scatter to that of the classical M BH − M BCG relation. Moreover, we study how gas accretion and BH-BH mergers contribute to SMBH growth across cosmic time. Methods. We employed 135 groups and clusters with a mass range 1.4 × 10 13 M − 2.5 × 10 15 M extracted from a set of 29 zoom-in cosmological hydro-dynamical simulations where the baryonic physics is treated with various sub-grid models, including feedback by active galactic nuclei. Results. In our simulations we find that M BH correlates well with M 500 and T 500 , with the scatter around these relations compatible within 2σ with the scatter around M BH − M BCG at z = 0. The M BH − M 500 relation evolves with time, becoming shallower at lower redshift as a direct consequence of hierarchical structure formation. On average, in our simulations the contribution of gas accretion to the total SMBH mass dominates for the majority of the cosmic time (z > 0.4), while in the last 2 Gyr the BH-BH mergers become a larger contributor. During this last process, substructures hosting SMBHs are disrupted in the merger process with the BCG and the unbound stars enrich the diffuse stellar component rather than increase BCG mass. Conclusions. From the results obtained in our simulations with simple sub-grid models we conclude that the scatter around the M BH − T 500 relation is comparable to the scatter around the M BH − M BCG relation and that, given the observational difficulties related to the estimation of the BCG mass, clusters temperature and mass can be a useful proxy for the SMBHs mass, especially at high redshift.

An excess of small-scale gravitational lenses observed in galaxy clusters

“…We also compared the projected halo concentration distributions of the simulated clusters with the observational sample. In addition, the agreement between our simulated sample and the observations in terms of stellar masses of the BCGs and of other massive galaxies has been discussed previously (104,105). The stellar mass function in the Hydrangea simulation suite also matches the observations (94).…”

X-ray signatures of black hole feedback: hot galactic atmospheres in IllustrisTNG and X-ray observations

“…They interpret the correlations between the SMBH mass and the hot atmospheres as a consequence of the chaotic cold accretion (CCA) of the gas condensed out of the turbulent X-ray atmosphere onto the central SMBH, whereby sustaining a self-regulated feedback loop. The result is consistent with a numerical study by Bassini et al (2019) who used simulated samples of galaxy clusters obtained from zoom-in simulations to show that SMBH mergers are too rare to establish the observed correlations by means of the central-limit theorem. This line of interpretation embraces the scenario in which the correlations between the central SMBHs and their host galaxy's properties are a direct result of a delicate feedback-regulated interaction between the SMBH and its host galaxy (Silk and Rees 1998;King 2003;Churazov et al 2005).…”

Feedback from Active Galactic Nuclei in Galaxy Groups

“…In sum, by comparing the different X-ray/optical scaling relations, it has emerged that the extended plasma (collisional) atmospheres seem to play a more fundamental role than small-scale (collisionless) stellar properties in the co-evolution of SMBH and groups. This is further supported by zoom-in cosmological simulations [319][320][321]. On the other hand, the slope (and scatter) of the current cosmological simulations still remain too low when compared with the observations (dotted lines in Figure 16), indicating the need to model more realistic feeding and feedback physics (see Section 4) into the coarse subgrid numerical modules.…”

“…The solid curves show the fitted observational relations from Gaspari et al [77] (green; together with the quoted log-normal scatter), Bogdán et al [76] (blue), and the "BCG" subsample of Lakhchaura et al [78] (red). The dashed lines show the predictions of cosmological simulations with AGN feedback (Illustris TNG, Truong et al [321]; DIANOGA, Bassini et al [319]). The gray data points are taken from the sample of Gaspari et al [77], which already included the smaller samples that were used by Bogdán et al [76] and Lakhchaura et al [78].…”