We present a new suite of hydrodynamical simulations and use it to study, in detail, black hole and galaxy properties. The high time, spatial and mass resolution, and realistic orbits and mass ratios, down to 1:6 and 1:10, enable us to meaningfully compare star formation rate (SFR) and BH accretion rate (BHAR) timescales, temporal behaviour and relative magnitude. We find that (i) BHAR and galaxy-wide SFR are typically temporally uncorrelated, and have different variability timescales, except during the merger proper, lasting ~0.2-0.3 Gyr. BHAR and nuclear (<100 pc) SFR are better correlated, and their variability are similar. Averaging over time, the merger phase leads typically to an increase by a factor of a few in the BHAR/SFR ratio. (ii) BHAR and nuclear SFR are intrinsically proportional, but the correlation lessens if the long-term SFR is measured. (iii) Galaxies in the remnant phase are the ones most likely to be selected as systems dominated by an active galactic nucleus (AGN), because of the long time spent in this phase. (iv) The timescale over which a given diagnostic probes the SFR has a profound impact on the recovered correlations with BHAR, and on the interpretation of observational data.
Building galaxy merger trees from a state-of-the-art cosmological hydrodynamics simulation, Horizon-AGN, we perform a statistical study of how mergers and smooth accretion drive galaxy morphologic properties above $z > 1$. More specifically, we investigate how stellar densities, effective radii and shape parameters derived from the inertia tensor depend on mergers of different mass ratios. We find strong evidence that smooth accretion tends to flatten small galaxies over cosmic time, leading to the formation of disks. On the other hand, mergers, and not only the major ones, exhibit a propensit…
Cosmic reionization put an end to the dark ages that came after the recombination era. Observations seem to favor the scenario where massive stars generating photons in low-mass galaxies were responsible for the bulk of reionization. Even though a possible contribution from accretion disks of active galactic nuclei (AGN) has been widely considered, they are currently thought to have had a minor role in reionization. Our aim is to study the possibility that AGN contributed to reionization not only through their accretion disks, but also through ionizing photons coming from the AGN jets interact…
Gas Accretion versus BH Merger driven Growth Modes of Supermassive Black Holes and Implications for the Little Red Dots
Istituto Nazionale di Astrofisica (INAF) - Osservatorio Astronomico di Trieste (OATs)（意大利国家天体物理研究所（INAF）- 的里雅斯特天文台（OATs））；Centro de Ciências Naturais e Humanas - Universidade Federal do ABC（自然与人类科学中心 - 圣保罗联邦ABC大学）；Núcleo de Astrofísica - Universidade Cidade de São Paulo（天体物理学核心 - 圣保罗城市大学）
We use a suite of hydrodynamical simulations of galaxy mergers to compare star formation rate (SFR) and black hole accretion rate (BHAR) for galaxies before the interaction ('stochastic' phase), during the `merger' proper, lasting ~0.2-0.3 Gyr, and in the `remnant' phase. We calculate the bi-variate distribution of SFR and BHAR and define the regions in the SFR-BHAR plane that the three phases occupy. No strong correlation between BHAR and galaxy-wide SFR is found. A possible exception are galaxies with the highest SFR and the highest BHAR. We also bin the data in the same way used in several …
Observations indicate that the dispersal of protoplanetary discs in star clusters occurs on time scales of about 5 Myr. Several processes are thought to be responsible for this disc dispersal. Here we compare two of these processes: dynamical encounters and interaction with the interstellar medium, which includes face-on accretion and ram pressure stripping. We perform simulations of embedded star clusters with parameterisations for both processes to determine the environment in which either of these processes is dominant. We find that face-on accretion, including ram pressure stripping, is th…
Radio-loud active galaxies have two accretion modes [radiatively inefficient (RI) and radiatively efficient (RE)], with distinct optical and infrared signatures, and two jet dynamical behaviours, which in arcsec- to arcmin-resolution radio surveys manifest primarily as centre- or edge-brightened structures [Fanaroff-Riley (FR) class I and II]. The nature of the relationship between accretion mode and radio morphology (FR class) has been the subject of long debate. We present a comprehensive investigation of this relationship for a sample of 286 well-resolved radio galaxies in the LOFAR Two-met…
The Narrow-Line Seyfert 1 Phenomenon: Accretion State Versus Host Galaxy Properties
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）
The rapid assembly of the massive black holes that power the luminous quasars observed at $z \sim 6-7$ remains a puzzle. Various direct collapse models have been proposed to head-start black hole growth from initial seeds with masses $\sim 10^5\,\rm M_\odot$, which can then reach a billion solar mass while accreting at the Eddington limit. Here we propose an alternative scenario based on radiatively inefficient super-critical accretion of stellar-mass holes embedded in the gaseous circum-nuclear discs (CNDs) expected to exist in the cores of high redshift galaxies. Our sub-pc resolution hydrod…
We investigate whether the hard X-ray photon index ($Γ$) versus accretion rate correlation for super-Eddington accreting quasars is different from that for sub-Eddington accreting quasars. We construct a sample of 113 bright quasars from the Sloan Digital Sky Survey Data Release 14 quasar catalog, including 38 quasars as the super-Eddington subsample and 75 quasars as the sub-Eddington subsample. We derive black-hole masses using a simple-epoch virial mass formula based on the ${\rm Hβ}$ lines, and we use the standard thin disk model to derive the dimensionless accretion rates ($\dot{\mathscr{…
We use a suite a cooling halo simulations to study a new mechanism for rapid accretion of hot halo gas onto star-forming galaxies. Correlated supernovae events create converging 'superbubbles' in the halo gas. Where these collide, the density increases, driving cooling filaments of low metallicity gas that feed the disc. At our current numerical resolution (20 pc) we are only able to resolve the most dramatic events; these could be responsible for the build-up of galaxy discs after the most massive gas-rich mergers have completed (z < 1). As we increase the numerical resolution, we find that t…
An essential part of the paradigm describing active galactic nuclei is the alignment between the radio jet and the associated rotation axis of the sub-pc sized accretion disks. Because of the small linear and angular scales involved, this alignment has not yet been checked in a sufficient number of Low Luminosity Active Galactic Nuclei (LLAGNs). The project intends to examine the validity of this paradigm by measuring the radio continuum on the same physical scale as the accretion disks, to investigate any possible connection between these disks and the radio continuum. We observed a sample of…
Stars form in regions of very inhomogeneous densities and may have chaotic orbital motions. This leads to a time variation of the accretion rate, which will spread the masses over some mass range. We investigate the mass distribution functions that arise from fluctuating accretion rates in non-linear accretion, $\dot{m} \propto m^α$. The distribution functions evolve in time and develop a power law tail attached to a lognormal body, like in numerical simulations of star formation. Small fluctuations may be modelled by a Gaussian and develop a power-law tail $\propto m^{-α}$ at the high-mass si…
We present a long-term, multi-wavelength project to understand the epoch of fastest growth of the most massive black holes by using a sample of 40 luminous quasars at z~4.8. These quasars have rather uniform properties, with typical accretion rates and black hole masses of L/L_Edd~0.7 and M_BH~10^9 M_sol. The sample consists of "FIR-bright" sources with a previous Herschel/SPIRE detection, suggesting SFR > 1000 M_sol/yr, as well as of "FIR-faint" sources for which Herschel stacking analysis implies a typical SFR of ~400 M_sol/yr. Six of the quasars have been observed by ALMA in [CII]λ157.74 mi…
From Liu and Han (2014), the accretion-dominated jet power has a linear proportionality with the accretion rate, whereas the power law index is <=0.5 at lower accretion rate. Attributing the jet power in low accretion rate AGN to the black hole spin, it implies that the jet power has a flatter spectrum than the accretion-dominated jet versus the accretion rate. The black hole must be spinning rapidly for producing such jet power efficiently, and this may allow us to find high-spin black holes in the radio-loud low-luminosity AGN.
We model the luminosity-dependent projected and redshift-space two-point correlation functions (2PCFs) of the Sloan Digital Sky Survey (SDSS) DR7 Main galaxy sample, using the halo occupation distribution (HOD) model and the subhalo abundance matching (SHAM) model and its extension. All the models are built on the same high-resolution $N$-body simulations. We find that the HOD model generally provides the best performance in reproducing the clustering measurements in both projected and redshift spaces. The SHAM model with the same halo-galaxy relation for central and satellite galaxies (or dis…
We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. We select the most massive dark matter halo at z=6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 10^5 Msun, and that seeding occurs around z~15 in dark matter haloes of mass 10^9-10^10 Msun, we find that it is possible to build up su…
To date, most of the luminous quasars known at $z\sim6$ have been found to be in maximal accretion with the Eddington ratios, $λ_{\rm{Edd}}\sim1$, suggesting enhanced nuclear activities in the early universe. However, this may not be the whole picture of supermassive black hole (SMBH) growth since previous studies have not reached on faint quasars that are more likely to harbor SMBHs with low $λ_{\rm{Edd}}$. To gain a better understanding on the accretion activities in quasars in the early universe, we obtained a deep near-infrared (NIR) spectrum of a quasar, IMS J220417.92+011144.8 (hereafter…
MRI Turbulence versus $α$-Viscosity in Circumbinary Disks: Implications for Gravitational-Wave Dephasing and Accretion Variability
Center for Cosmology and Particle Physics, Physics Department, New York University（纽约大学物理系宇宙学与粒子物理中心）；Center for Computational Astrophysics, Flatiron Institute（西蒙斯平顿研究所计算天体物理学中心）
We selected a sample of 28 Type 1 AGNs for which a black hole mass has been inferred using the reverberation mapping technique and single epoch scaling relations. All 28 sources show clear evidence of the "Big Blue Bump" in the optical-UV band whose emission is produced by an accretion disk (AD) around a supermassive black hole. We fitted the spectrum of these sources with the relativistic thin AD model KERRBB in order to infer the black hole masses and compared them with those from Reverberation mapping and Single epoch methods, discussing the possible uncertainties linked to such a model by …
We introduce algorithms for black hole physics, i.e., black hole formation, accretion and feedback, into the NIHAO (Numerical Investigation of a Hundred Astrophysical Objects) project of galaxy simulations. This enables us to study high mass, elliptical galaxies, where feedback from the central black hole is generally thought to have a significant effect on their evolution. We furthermore extend the NIHAO suite by 45 simulations that encompass $z=0$ halo masses from $1 \times 10^{12}$ to $4 \times 10^{13}\,\mathrm{M}_{\odot}$, and resimulate five galaxies from the original NIHAO sample with bl…
JWST Spectroscopic View of a Rapidly Growing Dust-obscured Quasar at $z \sim 4$: Effect of Dust Extinction Correction on Black Hole Mass and Eddington Ratio Estimation
We present simulation results for the formation and long-term evolution of a primordial protostellar disk harbored by a first star. Using a 2+1D nonaxisymmetric thin disk numerical simulation, together with a barotropic relation for the gas, we are able to probe ~20 kyr of the disk's evolution. During this time period we observe fragmentation leading to loosely bound gaseous clumps within the disk. These are then torqued inward and accreted onto the growing protostar, giving rise to a burst phenomenon. The luminous feedback produced by this mechanism may have important consequences for the sub…
The growing evidence for energy-conserving outflows in powerful and luminous AGN supports the idea that high-velocity winds launched from the accretion disc evolve systematically after undergoing a shock with the ambient medium and that they are capable to expel enough mass and energy so as to produce feedback. This talk will give an overview of recent results on AGN ultra fast outflows, with focus on grating X-ray spectra of bright sources. I will review how UFO work, their observational properties and their relation with AGN outflows in other bands, what is their impact on the host galaxies …
We address the nature of the giant clumps in high-z galaxies that undergo Violent Disc Instability, attempting to distinguish between long-lived clumps that migrate inward and short-lived clumps that disrupt by feedback. We study the evolution of clumps as they migrate through the disc using an analytic model tested by simulations and confront theory with CANDELS observations. The clump ``bathtub" model, which considers gas and stellar gain and loss, is characterized by four parameters: the accretion efficiency, the star-formation-rate (SFR) efficiency, and the outflow mass-loading factors for…
We report on the relation between the mass of supermassive black holes (SMBHs; M_BH) and that of hosting dark matter halos (M_h) for 49 z ~ 6 quasi-stellar objects (QSOs) with [CII]158um velocity-width measurements. Here, we estimate M_h assuming that the rotation velocity from FWHM_CII is equal to the circular velocity of the halo; we have tested this procedure using z ~ 3 QSOs that also have clustering-based M_h estimates. We find that a vast majority of the z ~ 6 SMBHs are more massive than expected from the local M_BH - M_h relation, with one-third of the sample by factors >~ 10^2. The med…
Super-massive black holes (SMBHs) with $M_{\bullet} \sim 10^9 $ M$_{\odot}$ at $z>6$ likely originate from massive seed black holes (BHs). We investigate the consequences of seeding SMBHs with direct collapse BHs (DCBHs) ($M_{\bullet}=10^{4-6}\, \mathrm{M}_\odot$) on proto-galactic disc growth. We show that even in the absence of direct feedback effects, the growth of seed BHs reduces the development of gravitational instabilities in host galaxy discs, suppressing star formation and confining stars to a narrow ring in the disc and leading to galaxies at $z \sim 6$ which lie above the local BH-…
The largest observed supermassive black holes (SMBHs) have a mass of M_BH ~ 10^{10} M_sun, nearly independent of redshift, from the local (z~0) to the early (z>6) Universe. We suggest that the growth of SMBHs above a few 10^{10} M_sun is prevented by small-scale accretion physics, independent of the properties of their host galaxies or of cosmology. Growing more massive BHs requires a gas supply rate from galactic scales onto a nuclear region as high as >10^3 M_sun/yr. At such a high accretion rate, most of the gas converts to stars at large radii (~10-100 pc), well before reaching the BH. We …
Using single-component fits to SDSS/UKIDSS images of galaxies in the G09 region of the GAMA survey we study radial colour gradients across the galaxy population. We use the multiwavelength information provided by MegaMorph analysis of galaxy light profiles to calculate intrinsic colour gradients, and divide into six subsamples split by overall Sérsic index ($n$) and galaxy colour. We find a bimodality in the colour gradients of high- and low-$n$ galaxies in all wavebands, which varies with overall galaxy luminosity. Global trends in colour gradients therefore result from combining the contrast…
We investigate the local supermassive black hole (SMBH) density function and relative mass accretion rates of all active galactic nuclei (AGNs) identified in a volume-limited sample of infrared (IR) bright galaxies (L_IR > 3 x 10^9 L_sun) to D<15 Mpc (Goulding & Alexander 2009). A database of accurate SMBH mass (M_BH) estimates is compiled from literature sources using physically motivated AGN modeling techniques (reverberation mapping, maser mapping and gas kinematics) and well-established indirect M_BH estimation methods (the M-sigma and M_BH-L_(K,bul) relations). For the three sources witho…
The James Webb Space Telescope (JWST) will have the sensitivity to detect early low-mass black holes as they transition from "seeds" to supermassive black holes (BHs). Based on the JAGUAR mock catalog of galaxies, we present a clean color selection that takes advantage of the unique UV slope of accreting supermassive black holes with relatively low mass and high accretion rates. We show for a range of host stellar masses that those galaxies hosting $\sim 10^{6} M_{\odot}$ BHs radiating at >10% of their Eddington luminosity separate in color space from inactive systems. Here we propose a set of…
Massive stars produce so much light that the radiation pressure they exert on the gas and dust around them is stronger than their gravitational attraction, a condition that has long been expected to prevent them from growing by accretion. We present three-dimensional radiation-hydrodynamic simulations of the collapse of a massive prestellar core and find that radiation pressure does not halt accretion. Instead, gravitational and Rayleigh-Taylor instabilities channel gas onto the star system through non-axisymmetric disks and filaments that self-shield against radiation, while allowing radiatio…
