1,721,161 research outputs found
The formation of galaxy stellar cores by the hierarchical merging of supermassive black holes
No full textThe assembly and merging history of supermassive black holes in hierarchical models of galaxy formation
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LISA detection of massive black hole binaries: imprint of seed populations and extreme recoils
No full textSize matters: are we witnessing super-Eddington accretion in high-redshift black holes from JWST?
Full text linkObservations by the James Webb Space Telescope of the Universe at z≳4 have shown that massive black holes (MBHs) appear to be extremely overmassive compared to the local correlation for active galactic nuclei. In some cases, these objects might even reach half the stellar mass inferred for the galaxy. It has become a great challenging for theoretical models to understand how these objects formed and grew to these masses. Different ideas range from heavy seed to super-Eddington accretion phases. We take a different approach and try to infer how accurate these MBH mass estimates are and whether we really need to revise our physical models. By considering how the emerging spectrum (both the continuum and the broad lines) of an accreting MBH changes close to and above the Eddington limit, we infer a much larger uncertainty in the MBH mass estimates relative to that of local counterparts. The uncertainty is up to an order of magnitude. We also infer a potential preference for lower masses and higher accretion rates, which i) moves accreting MBHs closer to the local correlations, and ii) might indicate that we witness a widespread phase of very rapid accretion for the first time
Super-Eddington accretion in high-redshift quasar hosts: Black-hole-driven outflows, galaxy quenching, and the nature of little red dots
No full textThe advent of the James Webb Space Telescope has revolutionised our understanding of the high-redshift Universe through its detection of bright, massive galaxies up to z ≳ 10 and its identification of peculiar sources called ‘little red dots’ (LRDs). The origin of both classes of objects remains uncertain but is likely linked to the formation and early growth of the first massive black holes (MBHs), which may be more easily explained by invoking phases of super-Eddington accretion. In this study, we used a state-of-the-art zoom-in cosmological simulation of a quasar host to investigate whether these objects could resemble any of the peculiar sources observed with JWST during their assembly. We find that the impact of MBH feedback on star formation is typically moderate, with outflows preferentially escaping perpendicular to the galactic disc. However, for approximately ten percent of the galaxy’s lifetime, the system enters a distinct quenched phase following rapid MBH growth driven by super-Eddington accretion. This phase culminates in a powerful feedback event, during which the MBH jet and disc-driven winds interact directly with the galactic disc and carve out a central cavity. We also find that, during the history of the quasar host progenitor, the spectral properties of the system can resemble both LRDs and quenched galaxies, depending on the specific evolutionary stage considered. These findings suggest that both conditions may represent transient phases in the life cycle of high-redshift galaxies
High-redshift quasars and their host galaxies - II. Multiphase gas and stellar kinematics
Full text linkObservations of z ≳ 6 quasars provide information on the early phases of the most massive black holes (MBHs) and galaxies. Current observations at sub-mm wavelengths trace cold and warm gases, and future observations will extend information to other gas phases and the stellar properties. The goal of this study is to examine the gas life cycle in a z ≳ 6 quasar: From accretion from the halo to the galaxy and all the way into the MBH, to how star formation and the MBH itself affect the gas properties. Using a very high resolution cosmological zoom-in simulation of a z = 7 quasar, including state-of-the-art non-equilibrium chemistry, MBH formation, growth, and feedback, we investigate the distribution of the different gas phases in the interstellar medium across cosmic time. We assess the morphological evolution of the quasar host using different tracers (star- or gas-based) and the thermodynamic distribution of the MBH accretion-driven outflows, finding that obscuration in the disc is mainly due to molecular gas, with the atomic component contributing at larger scales and/or above/below the disc plane. Moreover, our results also show that molecular outflows, if present, are more likely the result of gas being lifted near the MBH than production within the wind because of thermal instabilities. Finally, we also discuss how different gas phases can be employed to dynamically constrain the MBH mass, and argue that resolutions below ∼100 pc yield unreliable estimates because of the strong contribution of the nuclear stellar component to the potential at larger scales
The gravitational wave signal from massive black hole binaries and its contribution to the LISA data stream
No full textConstraining the high-redshift formation of black hole seeds in nuclear star clusters with gas inflows
No full textIn this paper, we explore a possible route of black hole seed formation that appeals to a model by Davies, Miller & Bellovary who considered the case of the dynamical collapse of a dense cluster of stellar black holes subjected to an inflow of gas. Here, we explore this case in a broad cosmological context. The working hypotheses are that (i) nuclear star clusters form at high redshifts in pre-galactic discs hosted in dark matter haloes, providing a suitable environment for the formation of stellar black holes in their cores, (ii) major central inflows of gas occur on to these clusters due to instabilities seeded in the growing discs and/or to mergers with other gas-rich haloes and (iii) following the inflow, stellar black holes in the core avoid ejection due to the steepening to the potential well, leading to core collapse and the formation of a massive seed of ≲1000M⊙. We simulate a cosmological box tracing the build-up of the dark matter haloes and their embedded baryons, and explore cluster evolution with a semi-analytical model.We showthat this route is feasible, peaks at redshifts z ≲10 and occurs in concomitance with the formation of seeds from other channels. The channel is competitive relative to others, and is independent of the metal content of the parent cluster. This mechanism of gas-driven core collapse requires inflows with masses at least 10 times larger than the mass of the parent star cluster, occurring on time-scales shorter than the evaporation/ejection time of the stellar black holes from the core. In this respect, the results provide upper limit to the frequency of this process.© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Modelling the merging history of binary SMBHs in hierarchical models of galaxy formation
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