Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

Supermassive black holes (BH) accrete gas from their surroundings and coalesce with companions during galaxy mergers, and both processes change the BH mass and spin. By means of high-resolution hydrodynamical simulations of galaxies, either idealised or embedded within the cosmic web, we explore the effects of interstellar gas dynamics and external perturbations on BH spin evolution. All these physical quantities were evolved on-the-fly in a self-consistent manner. We use a 'maximal' model to describe the turbulence induced by stellar feedback to highlight its impact on the angular momentum of the gas accreted by the BH. Periods of intense star formation are followed by phases where stellar feedback drives large-scale outflows and hot bubbles. We find that BH accretion is synchronised with star formation, as only when gas is cold and dense do both processes take place. During such periods, gas motion is dominated by consistent rotation. On the other hand, when stellar feedback becomes substantial, turbulent motion randomises gas angular momentum. However BH accretion is strongly suppressed in that case, as cold and dense gas is lacking. In our cosmological simulation, at very early times (z>6), the galactic disc has not yet settled and no preferred direction exists for the angular momentum of the accreted gas, so the BH spin remains low. As the gas settles into a disc (6>z>3), the BH spin then rapidly reaches its maximal value. At lower redshifts (z<3), even when galaxy mergers flip the direction of the angular momentum of the accreted gas, causing it to counter-rotate, the BH spin magnitude only decreases modestly and temporarily. Should this be a typical evolution scenario for BH, it potentially has dramatic consequences regarding their origin and assembly, as accretion on maximally spinning BH embedded in thin Shakura-Sunyaev disc is significantly reduced.

Abstract:

Supermassive black holes (BH) accrete gas from their surroundings and coalesce with companions during galaxy mergers, and both processes change the BH mass and spin. By means of high-resolution hydrodynamical simulations of galaxies, either idealised or embedded within the cosmic web, we explore the effects of interstellar gas dynamics and external perturbations on BH spin evolution. All these physical quantities were evolved on-the-fly in a self-consistent manner. We use a 'maximal' model to describe the turbulence induced by stellar feedback to highlight its impact on the angular momentum of the gas accreted by the BH. Periods of intense star formation are followed by phases where stellar feedback drives large-scale outflows and hot bubbles. We find that BH accretion is synchronised with star formation, as only when gas is cold and dense do both processes take place. During such periods, gas motion is dominated by consistent rotation. On the other hand, when stellar feedback becomes substantial, turbulent motion randomises gas angular momentum. However BH accretion is strongly suppressed in that case, as cold and dense gas is lacking. In our cosmological simulation, at very early times (z>6), the galactic disc has not yet settled and no preferred direction exists for the angular momentum of the accreted gas, so the BH spin remains low. As the gas settles into a disc (6>z>3), the BH spin then rapidly reaches its maximal value. At lower redshifts (z<3), even when galaxy mergers flip the direction of the angular momentum of the accreted gas, causing it to counter-rotate, the BH spin magnitude only decreases modestly and temporarily. Should this be a typical evolution scenario for BH, it potentially has dramatic consequences regarding their origin and assembly, as accretion on maximally spinning BH embedded in thin Shakura-Sunyaev disc is significantly reduced.

Abstract:

<jats:title>Abstract</jats:title> <jats:p> We analyse the large-scale angular clustering of quasars in the <jats:italic>Gaia</jats:italic> - <jats:italic>unWISE</jats:italic> quasar catalog, <jats:italic>Quaia</jats:italic> , and their cross-correlation with maps of the lensing convergence of the Cosmic Microwave Background (CMB), to constrain the level of primordial non-Gaussianity (PNG). Specifically, we target the scale-dependent bias that would be induced by PNG on biased tracers of the matter inhomogeneities on large scales. The <jats:italic>Quaia</jats:italic> sample is particularly well suited for this analysis, given the large effective volume covered, and our ability to map out the main potential sources of systematic contamination and mitigate their impact. Using the universality relation to characterise the response of the quasar overdensity to PNG ( <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1), we report constraints on the local-type PNG parameter   <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> of <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> = -20.5 <jats:sup>+19.0</jats:sup> <jats:sub>-18.1</jats:sub> (68% C.L.) by combining the quasar auto-correlation and its cross-correlation with CMB lensing in two tomographic redshift bins (or <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> = -28.7 <jats:sup>+26.1</jats:sup> <jats:sub>-24.6</jats:sub> if assuming a lower response for quasars, <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1.6). The error on <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> can be further improved if the cross-correlation between the tomographic redshift bins is included. Using the CMB lensing cross-correlations alone, we find <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> = -13.8 <jats:sup>+26.7</jats:sup> <jats:sub>-25.0</jats:sub> and <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> = -15.6 <jats:sup>+42.3</jats:sup> <jats:sub>-34.8</jats:sub> for <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1 and <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1.6 respectively. These are the tightest constraints on <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> to date from angular clustering statistics and cross-correlations with CMB lensing. </jats:p>

Abstract:

Claims of local ($z \lesssim 0.05$) anisotropy in the Hubble constant have been made based on direct distance tracers such as Tully–Fisher galaxies and Type Ia supernovae. We revisit these using the CosmicFlows-4 Tully–Fisher W1 subsample, 2MTF and SFI++ Tully–Fisher catalogues, and the Pantheon+ supernova compilation (all restricted to $z < 0.05$), including a dipole in either the Tully–Fisher zero-point or the standardized supernova absolute magnitude. Our forward-modelling framework jointly calibrates the distance relation, marginalizes over distances, and accounts for peculiar velocities using a linear-theory reconstruction. We compare the anisotropic and isotropic model using the Bayesian evidence. In the CosmicFlows-4 sample, we infer a zero-point dipole of amplitude $0.087 \pm 0.019$ mag, or $4.1\pm 0.9$ percent when expressed as a dipole in the Hubble parameter. This is consistent with previous estimates but at higher significance: model comparison yields odds of $877\!:\!1$ in favour of including the zero-point dipole. In Pantheon+ we infer zero-point dipole amplitude of $0.049 \pm 0.013$ mag, or $2.3\pm 0.6$ percent when expressed as a dipole in the Hubble parameter. However, by allowing for a radially varying velocity dipole, we show that the anisotropic zero-point model captures local flow features (or possibly systematics) in the data rather than an actual linearly growing effective bulk flow caused by anisotropy in the zero-point or expansion rate. Crucially, inferring a more general bulk flow curve we find results fully consistent with expectations from the standard cosmological model.