ABSTRACT
We present the results of nine simulations of radiatively inefficient magnetically arrested discs (MADs) across different values of the black hole spin parameter a*: −0.9, −0.7, −0.5, −0.3, ...0, 0.3, 0.5, 0.7, and 0.9. Each simulation was run up to $t \gtrsim 100\, 000\, GM/c^3$ to ensure disc inflow equilibrium out to large radii. We find that the saturated magnetic flux level, and consequently also jet power, of MAD discs depends strongly on the black hole spin, confirming previous results. Prograde discs saturate at a much higher relative magnetic flux and have more powerful jets than their retrograde counterparts. MADs with spinning black holes naturally launch jets with generalized parabolic profiles whose widths vary as a power of distance from the black hole. For distances up to 100GM/c2, the power-law index is k ≈ 0.27–0.42. There is a strong correlation between the disc–jet geometry and the dimensionless magnetic flux, resulting in prograde systems displaying thinner equatorial accretion flows near the black hole and wider jets, compared to retrograde systems. Prograde and retrograde MADs also exhibit different trends in disc variability: accretion rate variability increases with increasing spin for a* > 0 and remains almost constant for a* ≲ 0, while magnetic flux variability shows the opposite trend. Jets in the MAD state remove more angular momentum from black holes than is accreted, effectively spinning down the black hole. If powerful jets from MAD systems in Nature are persistent, this loss of angular momentum will notably reduce the black hole spin over cosmic time.
ABSTRACT
We study the link between supermassive black hole growth and the stellar mass assembly of their host galaxies in the state-of-the-art Romulus suite of simulations. The cosmological ...simulations Romulus25 and RomulusC employ innovative recipes for the seeding, accretion, and dynamics of black holes in the field and cluster environments, respectively. We find that the black hole accretion rate traces the star formation rate among star-forming galaxies. This result holds for stellar masses between 108 and 1012 solar masses, with a very weak dependence on host halo mass or redshift. The inferred relation between accretion rate and star formation rate does not appear to depend on environment, as no difference is seen in the cluster/proto-cluster volume compared to the field. A model including the star formation rate, the black hole-to-stellar mass ratio, and the cold gas fraction can explain about 70 per cent of all variations in the black hole accretion rate among star-forming galaxies. Finally, bearing in mind the limited volume and resolution of these cosmological simulations, we find no evidence for a connection between black hole growth and galaxy mergers, on any time-scale and at any redshift. Black holes and their galaxies assemble in tandem in these simulations, regardless of the larger scale intergalactic environment, suggesting that black hole growth simply follows star formation on galactic scales.
The dense environment of a galaxy cluster can radically transform the content of in-falling galaxies. Recent observations have found a significant population of active galactic nuclei (AGN) within ..."jellyfish galaxies," galaxies with trailing tails of gas and stars that indicate significant ram pressure stripping. The relationship between AGN and ram pressure stripping is not well understood. In this Letter, we investigate the connection between AGN activity and ram pressure in a fully cosmological setting for the first time using the RomulusC simulation, one of the highest resolution simulations of a galaxy cluster to date. For lower mass galaxies (with stellar masses M* 109.5 M ) both star formation and black hole accretion are suppressed by ram pressure before they reach pericenter, whereas for more massive galaxies accretion onto the black hole is enhanced during pericentric passage. Our analysis also indicates that as long as the galaxy retains gas, AGN with higher Eddington ratios are more likely to be found in galaxies experiencing higher ram pressure. We conclude that prior to quenching star formation, ram pressure triggers enhanced accretion onto the black hole, which in our model then produces heating and outflows due to AGN feedback. These simulations suggest that AGN feedback may in turn serve to aid in the quenching of star formation in tandem with ram pressure.
Abstract
A spinning black hole (BH) accreting from a disk of strongly magnetized plasma via a magnetically arrested disk is known to produce an efficient electromagnetic jet powered by the BH’s spin ...energy. We present general relativistic radiative magnetohydrodynamic simulations of magnetically arrested systems covering a range of sub- to super-Eddington accretion rates. Using the numerical results from these simulations, we develop formulae to describe the magnetization, jet efficiency, and spin evolution of an accreting BH as a function of its spin and accretion rate. A BH with near-Eddington accretion experiences a mild degree of spin-down because of angular momentum loss through the jet, leading to an equilibrium spin of 0.8 rather than 1.0 at the Eddington limit. As the accretion rate increases above Eddington, the spin-down effect becomes progressively stronger, ultimately converging on previous predictions based on nonradiative simulations. In particular, spin evolution drives highly super-Eddington systems toward a BH spin near zero. The formulae developed in this letter may be applied to galaxy- and cosmological-scale simulations that include BHs. If magnetically arrested disk accretion is common among supermassive BHs, the present results have broad implications for active galactic nucleus feedback and cosmological spin evolution.
Abstract
Dwarf galaxies are promising test beds for constraining models of supermassive and intermediate-mass black holes (MBHs) via their BH occupation fraction (BHOF). Disentangling seeding from ...the confounding effects of mass assembly over a Hubble time is a challenging problem that we tackle in this study with a suite of semianalytical models (SAMs). We show how the measured BHOF depends on the lowest BH mass or active galactic nucleus (AGN) luminosity achieved by a survey. To tell seeding models apart, we need to detect or model all AGNs brighter than 10
37
erg s
−1
in galaxies of
M
*
∼ 10
8−10
M
⊙
. Shallower surveys, like eRASS, cannot distinguish between seed models even with the compensation of a much larger survey volume. We show that the AMUSE survey, with its inference of the MBH population underlying the observed AGNs, strongly favors heavy seed models, growing with either a power-law Eddington ratio distribution function or one in which BH accretion is tied to the star formation rate (i.e., the AGN-main sequence, AGN-MS, model). These two growth channels can then be distinguished by the AGN luminosity function at >10
40
erg s
−1
, with the AGN-MS model requiring more accretion than observed at
z
∼ 0. Thus, current X-ray observations favor heavy seeds whose Eddington ratios follow a power-law distribution. The different models also predict different radio scaling relations, which we quantify using the fundamental plane of BH activity. We close with recommendations for the design of upcoming multiwavelength campaigns that can optimally detect MBHs in dwarf galaxies.
ABSTRACT
Faraday rotation has been seen at millimeter wavelengths in several low-luminosity active galactic nuclei, including Event Horizon Telescope (EHT) targets M87* and Sgr A*. The observed ...rotation measure (RM) probes the density, magnetic field, and temperature of material integrated along the line of sight. To better understand how accretion disc conditions are reflected in the RM, we perform polarized radiative transfer calculations using a set of general relativistic magnetohydrodynamic (GRMHD) simulations appropriate for M87*. We find that in spatially resolved millimetre wavelength images on event horizon scales, the RM can vary by orders of magnitude and even flip sign. The observational consequences of this spatial structure include significant time-variability, sign-flips, and non-λ2 evolution of the polarization plane. For some models, we find that internal RM can cause significant bandwidth depolarization even across the relatively narrow fractional bandwidths observed by the EHT. We decompose the linearly polarized emission in these models based on their RM and find that emission in front of the mid-plane can exhibit orders of magnitude less Faraday rotation than emission originating from behind the mid-plane or within the photon ring. We confirm that the spatially unresolved (i.e. image integrated) RM is a poor predictor of the accretion rate, with substantial scatter stemming from time variability and inclination effects. Models can be constrained with repeated observations to characterize time variability and the degree of non-λ2 evolution of the polarization plane.
Abstract
The recent Chandra-JWST discovery of a quasar in the
z
≈ 10.1 galaxy UHZ1 reveals that accreting supermassive black holes were already in place 470 million years after the Big Bang. The ...Chandra X-ray source detected in UHZ1 is a Compton-thick quasar with a bolometric luminosity of
L
bol
∼ 5 × 10
45
erg s
−1
, which corresponds to an estimated black hole (BH) mass of ∼4 × 10
7
M
⊙
, assuming accretion at the Eddington rate. JWST NIRCAM and NIRSpec data yield a stellar mass estimate for UHZ1 comparable to its BH mass. These characteristics are in excellent agreement with prior theoretical predictions for a unique class of transient, high-redshift objects, overmassive black hole galaxies (OBGs) by Natarajan et al., that harbor a heavy initial black hole seed that likely formed from the direct collapse of the gas. Given the excellent agreement between the observed multiwavelength properties of UHZ1 and theoretical model template predictions, we suggest that UHZ1 is the first detected OBG candidate. Our assertion rests on multiple lines of concordant evidence between model predictions and the following observed properties of UHZ1: its X-ray detection and the estimated ratio of the X-ray flux to the IR flux, which is consistent with theoretical expectations for a heavy initial BH seed; its high measured redshift of
z
≈ 10.1, as predicted for the transient OBG stage (9 <
z
< 12); the amplitude and shape of the detected JWST spectral energy distribution (SED) between 1 and 5
μ
m, which is in very good agreement with simulated template SEDs for OBGs; and the extended JWST morphology of UHZ1, which is suggestive of a recent merge and is also expected for the formation of transient OBGs. As the first OBG candidate, UHZ1 provides compelling evidence for the formation of heavy initial seeds from direct collapse in the early Universe.
Abstract
We present estimates for the number of shadow-resolved supermassive black hole (SMBH) systems that can be detected using radio interferometers, as a function of angular resolution, flux ...density sensitivity, and observing frequency. Accounting for the distribution of SMBHs across mass, redshift, and accretion rate, we use a new semianalytic spectral energy distribution model to derive the number of SMBHs with detectable and optically thin horizon-scale emission. We demonstrate that (sub)millimeter interferometric observations with ∼0.1
μ
as resolution and ∼1
μ
Jy sensitivity could access >10
6
SMBH shadows. We then further decompose the shadow source counts into the number of black holes for which we could expect to observe the first- and second-order lensed photon rings. Accessing the bulk population of first-order photon rings requires ≲2
μ
as resolution and ≲0.5 mJy sensitivity, whereas doing the same for second-order photon rings requires ≲0.1
μ
as resolution and ≲5
μ
Jy sensitivity. Our model predicts that with modest improvements to sensitivity, as many as ∼5 additional horizon-resolved sources should become accessible to the current Event Horizon Telescope (EHT), whereas a next-generation EHT observing at 345 GHz should have access to ∼3 times as many sources. More generally, our results can help guide enhancements of current arrays and specifications for future interferometric experiments that aim to spatially resolve a large population of SMBH shadows or higher-order photon rings.
The Event Horizon Telescope (EHT) has released analyses of reconstructed images of horizon-scale millimeter emission near the supermassive black hole at the center of the M87 galaxy. Parts of the ...analyses made use of a large library of synthetic black hole images and spectra, which were produced using numerical general relativistic magnetohydrodynamics fluid simulations and polarized ray tracing. In this article, we describe the PATOKA pipeline, which was used to generate the Illinois contribution to the EHT simulation library. We begin by describing the relevant accretion systems and radiative processes. We then describe the details of the three numerical codes we use, iharm, ipole, and igrmonty, paying particular attention to differences between the current generation of the codes and the originally published versions. Finally, we provide a brief overview of simulated data as produced by PATOKA and conclude with a discussion of limitations and future directions.
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