Rm BH Research Articles

Early-type galaxy speciation: elliptical (E) and ellicular (ES) galaxies in the Mbh–M*,sph diagram, and a merger-driven explanation for the origin of ES galaxies, antitruncated stellar discs in lenticular (S0) galaxies, and the Sérsicification of E galaxy light profiles

ABSTRACT In a recent series of papers, supermassive black holes were used to discern pathways in galaxy evolution. By considering the black holes’ coupling with their host galaxy’s bulge/spheroid, the progression of mass within each component has shed light on the chronological sequence of galaxy speciation. Offsets between the galaxy-morphology-dependent $M_{\rm bh}$–$M_{\rm \star ,sph}$ scaling relations trace a pattern of ‘punctuated equilibrium’ arising from merger-driven transitions between galaxy types, such as from spirals to dust-rich lenticulars and further to ‘ellicular’ and elliptical galaxies. This study delves deeper into the distinction between the ellicular galaxies – characterised by their intermediate-scale discs – and elliptical galaxies. Along the way, it is shown how some antitruncated large-scale discs in lenticular galaxies can arise from the coexistence of a steep intermediate-scale disc and a relatively shallow large-scale disc. This observation undermines application of the popular exponential-disc plus Sérsic-bulge model for lenticular galaxies and suggests some past bulge mass measurements have been overestimated. Furthermore, it is discussed how merger-driven disc-heating and blending likely leads to the spheroidalisation of discs and the conglomeration of multiple discs leads to the (high-n) Sérsicification of light profiles. The ellicular and elliptical galaxy distribution in the $M_{\rm bh}$–$M_{\rm \star ,sph}$ diagram is explored relative to major-merger-built lenticular galaxies and brightest cluster galaxies. The super-quadratic $M_{\rm bh}$–$M_{\rm \star }$ relations, presented herein, for merger-built systems should aid studies of massive black hole collisions and the gravitational wave background. Finally, connections to dwarf compact elliptical and ultracompact dwarf galaxies, with their 100–1000 times higher $M_{\rm bh}/M_{\rm \star ,sph}$ ratios, are presented.

Exploring MBH–P scaling relations in spiral galaxies: a comparative analysis of inner and outer arm structures

ABSTRACT We study the galactic spiral arm pitch angle dependence with wavelength as predicted by the density wave theory. A sample of 10 barred and unbarred spiral galaxies with two distinct, well-defined arms is used for the measurements. The data sample consists of galaxies with inner arms and galaxies with both inner and outer arms. We use six wavebands, namely 3.6 $\mu$m, 8.0 $\mu$m, B band, H $\alpha$, H i, and CO for the image analysis. The pitch angles are visually measured with the python-ol script and more precise measurements are obtained using spirality. We find a 1:1 correlation between pitch angle measurements in the 3.6 and 8.0 $\mu$m bands. We predict supermassive black hole (SMBH) masses for 3.6 $\mu$m waveband pitch angles using a standard scaling relation. We find that the black hole mass of a galaxy with both inner and outer arms is determined by the average pitch angle of the inner arms. Using only galaxies with inner arms, we find an SMBH mass–pitch angle relation of $\log (M_{\rm BH}/\mathrm{M}_\odot)=(7.11 \pm 0.33)+(0.003 \pm 0.017){\textit P}$. Using only galaxies with both inner and outer arms, we find an SMBH mass–pitch angle relation of $\log (M_{\rm BH}/\mathrm{M}_\odot)=(7.56 \pm 0.28)-(0.038 \pm 0.013){\textit P}$.

Ne v] emission from a faint epoch of reionization-era galaxy: evidence for a narrow-line intermediate-mass black hole

ABSTRACT Here, we present high spectral resolution ${\it JWST}$ NIRSpec observations of GN 42437, a low-mass (log(M$_\ast /{\rm M}_\odot)=7.9$), compact ($r_e \lt 500$pc), extreme starburst galaxy at $z=5.59$ with 13 emission-line detections. GN 42437 has a low metallicity (5–10 per cent Z$_\odot$) and its rest-frame H$\alpha$ equivalent width suggests nearly all of the observed stellar mass formed within the last 3 Myr. GN 42437 has an extraordinary 7$\sigma$ significant [Ne v] 3427 Å detection. The [Ne v] line has a rest-frame equivalent width of $11\pm 2$Å, [Ne v]/H$\alpha =0.04\pm 0.007$, [Ne v]/[Ne iii] 3870Å $= 0.26\pm 0.04$, and [Ne v]/He ii 4687Å $ = 1.2\pm 0.5$. Ionization from massive stars, shocks, or high-mass X-ray binaries cannot simultaneously produce these [Ne v] and other low-ionization line ratios. Reproducing the complete nebular structure requires both massive stars and accretion on to a black hole. We do not detect broad lines nor do the traditional diagnostics indicate that GN 42437 has an accreting black hole. Thus, the very high-ionization emission lines powerfully diagnose faint narrow-line black holes at high redshift. We approximate the black hole mass in a variety of ways as log(M$_{\rm BH}/{\rm M}_\odot) \sim 5{-}7$. This black hole mass is consistent with local relations between the black hole mass and the observed velocity dispersion, but significantly more massive than the stellar mass would predict. Very high-ionization emission lines may reveal samples to probe the formation and growth of the first black holes in the universe.

Discovery of a hyperluminous quasar at z = 1.62 with Eddington ratio >3 in the eFEDS field confirmed by KOOLS-IFU on Seimei Telescope

Abstract We report the discovery of a hyperluminous type 1 quasar (eFEDS J082826.9-013911; eFEDS J0828-0139) at $z_{\rm spec} = 1.622$ with a super-Eddington ratio ($\lambda _{\rm Edd}$). We perform the optical spectroscopic observations with KOOLS-IFU (the Kyoto Okayama Optical Low-dispersion Spectrograph with optical fiber) on the Seimei Telescope. The black hole mass ($M_{\rm BH}$) based on the single-epoch method with Mg ii $\lambda$2798 is estimated to be $M_{\rm BH} = {(6.2 \pm 1.2) }\times 10^8\, M_{\odot }$. To measure the precise infrared luminosity ($L_{\rm IR}$), we obtain submillimeter data taken by SCUBA-2 on the James Clerk Maxwell Telescope and conduct the spectral energy distribution analysis with X-ray to submillimeter data. We find that $L_{\rm IR}$ of eFEDS J0828-0139 is $L_{\rm IR} = {(6.8 \pm 1.8)} \times 10^{13}\, L_{\odot }$, confirming the existence of a hypeluminous infrared galaxy. $\lambda _{\rm Edd}$ is estimated to be $\lambda _{\rm Edd} = {3.6 \pm 0.7}$, making it a quasar with one of the highest BH mass accretion rates at cosmic noon.

Radiation and outflow properties of super-Eddington accretion flows around various mass classes of black holes: Dependence on the accretion rates

Abstract We perform axisymmetric two-dimensional radiation-hydrodynamic simulations of super-Eddington accretion flow and outflow around black holes to examine the properties of radiation and outflow as functions of the black hole mass and the accretion rate on to the black hole ($\dot{M}_{\rm BH}$). We find that the $\dot{m}_{\rm BH} ({\equiv} \dot{M}_{\rm BH}c^2 /L_{\rm Edd})$ dependence of $L_{\rm rad}/L_{\rm Edd}$ and $L_{\rm mech}/L_{\rm Edd}$ found for a stellar-mass black hole can apply to the high-mass cases, where $L_{\rm rad}$ is the radiation luminosity, $L_{\rm mech}$ is the mechanical luminosity, c is the speed of light, and $L_{\rm Edd}$ is the Eddington luminosity. Such universalities can appear in the regime in which electron scattering opacity dominates over absorption opacity. Further, the normalized isotropic mechanical luminosity $L_{\rm mech}^{\rm ISO}/L_{\rm Edd}$ (evaluated by normalized density and velocity at $\theta =10^\circ$) exhibits a broken power-law relationship with ${\dot{m}}_{\rm BH}$; $L_{\rm mech}^{\rm ISO}/ L_{\rm Edd} \propto {\dot{m}}_{\rm BH}^{2.7}$ (or $\propto {\dot{m}}_{\rm BH}^{0.7}$) below (above) ${\dot{m}}_{\rm BH}\sim 400$. This is because the radial velocity stays nearly constant (or even decreases) below (above) the break with increase of $\dot{m}_{\rm BH}$. We also find that the luminosity ratio is $L_{\rm mech}/L_{\rm rad}^{\rm ISO} \sim 0.05$ at ${\dot{m}}_{\rm BH} \sim 100$, which is roughly consistent with the observations of NLS1, 1H 0323+103.

XMM–Newton Ultra Narrow Deep Field survey – II. X-ray spectral analysis of the brightest AGN population

ABSTRACT In this work, we present the results of a detailed X-ray spectral analysis of the brightest active galactic nuclei (AGNs) detected in the XMM–Newton 1.75 Ms Ultra Narrow Deep Field. We analysed 23 AGNs that have a luminosity range of $\sim 10^{42} {\!-\!} 10^{46}\, \rm {erg}\, \rm {s}^{-1}$ in the $2 {\!-\!} 10\, \rm {keV}$ energy band, redshifts up to 2.66, and $\sim 10\,000$ X-ray photon counts in the $0.3{ \!-\! }10\, \rm {keV}$ energy band. Our analysis confirms the ‘Iwasawa–Taniguchi effect,’ an anticorrelation between the X-ray luminosity ($L_x$) and the Fe–k$\alpha$ equivalent width (${\rm EW}_{\rm Fe}$) possibly associated with the decreasing of the torus covering factor as the AGN luminosity increases. We investigated the relationship among black hole mass ($M_{\rm BH}$), $L_x$, and X-ray variability, quantified by the Normalized Excess Variance ($\sigma ^2_{\rm rms}$). Our analysis suggest an anticorrelation in both $M_{\rm BH} - \sigma ^2_{\rm rms}$ and $L_x- \sigma ^2_{\rm rms}$ relations. The first is described as $\sigma ^2_{\rm rms} \propto M^{-0.26 \pm 0.05}_{\rm BH}$, while the second presents a similar trend with $\sigma ^2_{\rm rms} \propto L_{x}^{-0.31 \pm 0.04}$. These results support the idea that the luminosity–variability anticorrelation is a byproduct of an intrinsic relationship between the BH mass and the X-ray variability, through the size of the emitting region. Finally, we found a strong correlation among the Eddington ratio ($\lambda _{\rm Edd}$), the hard X-ray photon index ($\Gamma$), and the illumination factor $\log (A)$, which is related to the ratio between the number of Compton scattered photons and the number of seed photons. The $\log (\lambda _{\rm Edd})-\Gamma -\log (A)$ plane could arise naturally from the connection between the accretion flow and the hot corona.

Accretion properties of a low-mass active galactic nucleus: UGC 6728

ABSTRACT We present a comprehensive analysis of approximately 15 years (2006–2021) of X-ray observations of UGC 6728, a low-mass bare AGN, for the first time. Our study encompasses both spectral and temporal aspects of this source. The spectral properties of this source are studied using various phenomenological and physical models. We conclude that (a) the observed variability in X-ray luminosity is not attributed to the hydrogen column density (NH) as UGC 6728 exhibits a bare nucleus, implying a negligible NH contribution along the line of sight, and (b) the spectral slope in the X-ray band demonstrates a systematic variation over time, indicating a transition from a relatively hard state to a comparatively soft state. We propose that the underlying accretion dynamics around the central object account for this behaviour. By performing X-ray spectral fitting, we estimate the mass of the central supermassive black hole (SMBH) in UGC 6728 to be $M_{\rm BH}=(7.13\pm 1.23)\times 10^5$ M$_\odot$. Based on our spectral and temporal analysis, we suggest that UGC 6728 lacks a prominent Compton hump or exhibits a very subtle hump that remains undetectable in our analysis. Furthermore, the high-energy X-ray photons in this source are likely to originate from the low-energy X-ray photons through inverse Compton scattering in a Compton cloud, highlighting a connection between the emission in two energy ranges. We noticed a strong soft excess component in the initial part of our observations, which was later reduced substantially. This variation of soft excess is explained in view of accretion dynamics.

Discovery of evolving low-frequency QPOs in hard X-rays (∼100 keV) observed in black hole Swift J1727.8−1613 with AstroSat

ABSTRACT We report the first detection of evolving low-frequency quasi-periodic oscillation (LFQPO) frequencies in hard X-rays upto 100 keV with AstroSat/LAXPC during ‘unusual’ outburst phase of Swift J1727.8−1613 in hard intermediate state (HIMS). The observed LFQPO in 20–100 keV has a centroid $\nu _{_{\rm QPO}}=1.43$ Hz, a coherence factor Q = 7.14 and an amplitude ${\rm rms_{_{\rm QPO}}} = 10.95{{\ \rm per\ cent}}$ with significance σ = 5.46. Type-C QPOs (1.09–2.6 Hz) are found to evolve monotonically during HIMS of the outburst with clear detection in hard X-rays (80−100 keV), where ${\rm rms_{_{\rm QPO}}}$ decreases ($\sim 12\!-\!3{{\ \rm per\ cent}}$) with energy. Further, $\nu _{_{\rm QPO}}$ is seen to correlate (anticorrelate) with low- (high-) energy flux in 2–20 keV (15–50 keV). Wide-band (0.7−40 keV) energy spectrum of NICER/XTI and AstroSat/LAXPC is satisfactorily described by the ‘dominant’ thermal Comptonization contribution (∼88 per cent) in presence of a ‘weak’ signature of disc emissions (kTin ∼ 0.36 keV) indicating the harder spectral distribution. Considering source mass $M_{\rm BH}=10\, \mathrm{M}_\odot$ and distance 1.5 < d (kpc) < 5, the unabsorbed bolometric luminosity is estimated as $\sim 0.03\!-\!0.92{{\ \rm per\ cent}}\, L_{\rm Edd}$. Finally, we discuss the implications of our findings in the context of accretion dynamics around black hole X-ray binaries.

Hα reverberation mapping from broad-band photometry of dwarf seyfert 1 galaxy NGC 4395

Abstract NGC 4395 is a dwarf Seyfert 1 galaxy with a possible intermediate-mass black hole of several $\rm {10^4}$ solar masses in its center. As a well-studied object, its broad line region size has been measured via H$\rm {\alpha }$ time lag in numerous spectroscopic reverberation mapping (SRM) and narrow-band photometric reverberation mapping (PRM) campaigns. Here we present its H$\rm {\alpha }$ time lag measurement using broad-band photometric data, with the application of our newly-developed ICCF-Cut method as well as the JAVELIN and χ2 methods. utilizing the minute-cadence multi-band light curves obtained from the $\rm {2}$m FTN and $\rm {10.4}$m GTC telescopes in recent works, we measured its H$\rm {\alpha }$ lag as approximately 40 ∼ 90 minutes from broad-band PRM. With the H$\rm {\alpha }$ emission line velocity dispersion, we calculated its central black hole mass as $\rm M_{\rm BH} = (8\pm 4) \times 10^3\, M_{\rm \odot }$. These results are comparable with previous results obtained by narrow-band PRM and SRM, providing further support to an intermediate-mass black hole in NGC 4395. In addition, our study also validates the ICCF-Cut as an effective method for broad-band PRM, which holds the potential for widespread application in the era of large multi-epoch, high-cadence photometric surveys.

The eROSITA final equatorial-depth survey (eFEDS): host-galaxy demographics of X-ray AGNs with Subaru Hyper Suprime-Cam

ABSTRACT We investigate the physical properties, such as star-forming activity, disc versus bulge nature, galaxy size, and obscuration of 3811 SRG/eROSITA-detected AGNs at 0.2 < z < 0.8 in the eFEDS field. Using Subaru Hyper Suprime-Cam imaging data in the grizy bands, we measure the structural and stellar properties for their host galaxies by performing a 2D AGN-host image decomposition. We find that (1) AGNs can contribute significantly to the total optical light down to ${\rm log}\, L_{\rm X}\sim 42.5\ \rm erg\ s^{-1}$, thus ignoring the AGN component can significantly bias the structural measurements; (2) AGN hosts are predominately star-forming galaxies at ${\rm log}\, \mathcal {M}_\star \lesssim 11.3\, \mathrm{M}_\odot$; (3) the bulk of AGNs (64 per cent) reside in galaxies with significant stellar discs ($\rm S\acute{e}rsic$ index n < 2), while their host galaxies become increasingly bulge dominated (n ∼ 4) and quiescent at ${\rm log}\, \mathcal {M}_\star \gtrsim 11.0\, \mathrm{M}_\odot$; (4) the size–stellar mass relation of AGN hosts tends to lie between that of inactive (i.e. non-AGN) star-forming, and quiescent galaxies, suggesting that the physical mechanism responsible for building the central stellar density also efficiently fuel the black hole growth; (5) the hosts of X-ray unobscured AGNs are biased towards face-on systems, suggesting that some of the obscuration of the nuclei could come from galaxy-scale gas and dust. This will bias against the detection of unobscured AGNs in gas-rich star-forming galaxies, which may partly account for the deficiency of star-forming discs as host galaxies for the most massive AGNs (missing star-forming fraction up to $\sim 40{{\ \rm per\ cent}}$). Our results are consistent with a scenario in which the black hole and galaxy transform in structure and star-forming activity while grow in mass, as desired to establish the local $\mathcal {M}_{\rm BH}-\mathcal {M}_{\rm bulge}$ relation.

Supermassive black hole mass in the massive elliptical galaxy M87 from integral-field stellar dynamics using OASIS and MUSE with adaptive optics: assessing systematic uncertainties

ABSTRACT The massive elliptical galaxy M87 has been the subject of several supermassive black hole mass measurements from stellar dynamics, gas dynamics, and recently the black hole shadow by the Event Horizon Telescope. This uniquely positions M87 as a benchmark for alternative black hole mass determination methods. Here, we use stellar kinematics extracted from integral-field spectroscopy observations with adaptive optics using Multi Unit Spectroscopic Explorer (MUSE) and Optically Adaptive System for Imaging Spectroscopy (OASIS). We exploit our high-resolution integral field spectroscopy to spectrally decompose the central actice galactic nuclei (AGNs) from the stars. We derive an accurate inner stellar-density profile and find it is flatter than previously assumed. We also use the spectrally extracted AGNs as a reference to accurately determine the observed MUSE and OASIS AO PSF. We then perform Jeans anisotropic modelling, with a new flexible spatially variable anisotropy, and measure the anisotropy profile, stellar mass-to-light variations, inner dark matter fraction, and black hole mass. Our preferred black hole mass is MBH = (8.7 ± 1.2[random] ± 1.3[systematic]) × 109 M⊙. However, using the inner stellar density from previous studies, we find a preferred black hole mass of $M_{\rm BH} = (5.5^{+0.5}_{-0.3}) \times 10^9 \ M_\odot$, consistent with previous work. We find that this is the primary cause of the difference between our results and previous work, in addition to smaller contributions due to kinematics and modelling method. We conduct numerous systematic tests of the kinematics and model assumptions and conclude that uncertainties in the black hole mass of M87 from previous determinations may have been underestimated and further analyses are needed.

FOREVER22: Gas and metal outflow from massive galaxies in protocluster regions

Abstract We study gas and metal outflow from massive galaxies in protocluster regions at z = 3 − 9 by using the results of FOREVER22 simulation projects. Our simulations contain massive haloes with $M_{\rm h} \gtrsim 10^{13}~\rm {\rm M}_{\odot }$, showing high star formation rates of $> 100~\rm {\rm M}_{\odot }~yr^{-1}$ and hosting supermassive black holes with $M_{\rm BH} \gtrsim 10^{8}~\rm {\rm M}_{\odot }$. We show that the mass loading factor (ηM) sensitively depends on the halo mass and it is ηM = 1.2 (9.2) for $M_{\rm h}= 10^{13}~(10^{11})~{\rm {\rm M}_{\odot }}$. Once the halo mass exceeds $\sim 10^{12.5}~\rm {\rm {\rm M}_{\odot }}$, the outflow velocity of the gas rapidly decreases near a virial radius, and the gas returns to a galactic centre finally as a fountain flow. Also, the metal inflow and outflow rates sensitively depend on the halo mass and redshift. At z = 3, the inflow rate becomes larger than the outflow one if $M_{\rm h}\gtrsim 10^{13.0}~{\rm {\rm M}_{\odot }}$. Thus, we suggest that massive haloes cannot be efficient metal enrichment sources beyond virial radii that will be probed in future observations, e.g., studies of metal absorption lines with the Prime Focus Spectrograph on the Subaru telescope.

Probing z ≳ six massive black holes with gravitational waves

ABSTRACT We investigate the coalescence of massive black hole ($M_{\rm BH}\gtrsim 10^{6}~\rm {\rm M}_{\odot }$) binaries (MBHBs) at 6 < z < 10 by adopting a suite of cosmological hydrodynamical simulations of galaxy formation, zoomed-in on biased (>3σ) overdense regions (Mh ∼ 1012 M⊙ dark matter haloes at z = 6) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Our simulations predict merger rates that range between 3 and 15 $\rm yr^{-1}$ at z ∼6, depending on the run considered, and after correcting for a bias factor of ∼20−30. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at z > 6. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR > 5) to range between 66 per cent and 69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals ($\mathcal {M}_c\sim 10^6~{{\rm M}_{\odot }}$ at z = 6), is around 10 $\rm deg^2$.

Gravothermal collapse of self-interacting dark matter halos as the origin of intermediate mass black holes in Milky Way satellites

Milky Way (MW) satellites exhibit a diverse range of internal kinematics, reflecting in turn a diverse set of subhalo density profiles. These profiles include large cores and dense cusps, which any successful dark matter model must explain simultaneously. A plausible driver of such diversity is self-interactions between dark matter particles (SIDM) if the cross section passes the threshold for the gravothermal collapse phase at the characteristic velocities of the MW satellites. In this case, some of the satellites are expected to be hosted by subhalos that are still in the classical SIDM core phase, while those in the collapse phase would have cuspy inner profiles, with a SIDM-driven intermediate mass black hole (IMBH) in the centre as a consequence of the runaway collapse. We develop an analytical framework that takes into account the cosmological assembly of halos and is calibrated to previous simulations; we then predict the timescales and mass scales ($M_{\rm BH}$) for the formation of IMBHs in velocity-dependent SIDM (vdSIDM) models as a function of the present-day halo mass, $M_0$. Finally, we estimate the region in the parameter space of the effective cross section and $M_0$ for a subclass of vdSIDM models that result in a diverse MW satellite population, as well as their corresponding fraction of SIDM-collapsed halos and those halos' inferred IMBH masses. We predict the latter to be in the range $0.1-1000~ {\rm M_\odot}$ with a $M_{\rm BH}-M_0$ relation that has a similar slope, but lower normalization, than the extrapolated empirical relation of super-massive black holes found in massive galaxies.

In situextreme mass ratio inspirals via subparsec formation and migration of stars in thin, gravitationally unstable AGN discs

ABSTRACTWe investigate the properties of stars born via gravitational instability in accretion discs around supermassive black holes (SMBHs) in active galactic nuclei (AGNs), and how this varies with the SMBH mass, accretion rate, or viscosity. We show with geometrically thin, steady-state disc solutions that fragmentation results in different populations of stars when one considers the initial conditions (e.g. density and temperature of the gravitationally unstable regions). We find that opacity gaps in discs around $10^6 \, {\rm M}_{\odot }$ SMBHs can trigger fragmentation at radii ≲ 10−2 pc, although the conditions lead to the formation of initially low stellar masses primarily at $0.1\!-\!0.5 \, {\rm M}_{\odot }$. Discs around more massive SMBHs ($M_{\rm BH} =10^{7-8} \, {\rm M}_{\odot }$) form moderately massive or supermassive stars (the majority at $10^{0-2} \, {\rm M}_{\odot }$). Using linear migration estimates, we discuss three outcomes: stars migrate till they are tidally destroyed, accreted as extreme mass ratio inspirals (EMRIs), or leftover after disc dispersal. For a single-AGN activity cycle, we find a lower limit for the EMRI rate $R_{\rm emri}\sim 0\!-\!10^{-4} \, \rm yr^{-1}$ per AGN assuming a star formation efficiency $\epsilon =1\!-\!30{{\ \rm per\ cent}}$. In cases where EMRIs occur, this implies a volumetric rate up to $0.5\!-\!10 \, \rm yr^{-1}\, Gpc^{-3}$ in the local Universe. The rates are particularly sensitive to model parameters for $M_{\rm BH}=10^6 \, {\rm M}_{\odot }$, for which EMRIs only occur if stars can accrete to 10s of solar masses. Our results provide further evidence that gas-embedded EMRIs can contribute a substantial fraction of events detectable by milliHz gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). Our disc solutions suggest the presence of migration traps, as has been found for more massive SMBH discs. Finally, the surviving population of stars after the disc lifetime leaves implications for stellar discs in galactic nuclei.

Numerical-relativity simulation for tidal disruption of white dwarfs by a supermassive black hole

We study tidal disruption of white dwarfs in elliptic orbits with the eccenticity of $\sim 1/3$--$2/3$ by a non-spinning supermassive black hole of mass $M_{\rm BH}=10^5M_\odot$ in fully general relativistic simulations targeting the extreme mass-ratio inspiral leading eventually to tidal disruption. Numerical-relativity simulations are performed by employing a suitable formulation in which the weak self-gravity of white dwarfs is accurately solved. We reconfirm that tidal disruption occurs for white dwarfs of the typical mass of $\sim 0.6M_\odot$ and radius $\approx 1.2 \times 10^4$\,km near the marginally bound orbit around a non-spinning black hole with $M_{\rm BH}\alt 4\times 10^5M_\odot$.

Splitting the lentils: Clues to galaxy/black hole coevolution from the discovery of offset relations for non-dusty versus dusty (wet-merger-built) lenticular galaxies in theMbh–M*,spheroid andMbh–M*,galaxy diagrams

ABSTRACTThis work advances the (galaxy morphology)-dependent (black hole mass, Mbh)–(spheroid/galaxy stellar mass, M*) scaling relations by introducing ‘dust bins’ for lenticular (S0) galaxies. Doing so has led to the discovery of Mbh–M*,sph and Mbh–M*,gal relations for dusty S0 galaxies – built by major wet mergers and comprising half the S0 sample – offset from the distribution of dust-poor S0 galaxies. The situation is reminiscent of how major dry mergers of massive S0 galaxies have created an offset population of ellicular and elliptical galaxies. For a given Mbh, the dust-rich S0 galaxies have 3–4 times higher M*,sph than the dust-poor S0 galaxies, and the steep distributions of both populations in the Mbh–M*,sph diagram bracket the $M_{\rm bh} \propto M_{\rm *,sph}^{2.27+/-0.48}$ relation defined by the spiral galaxies, themselves renovated through minor mergers. The new relations offer refined means to estimate Mbh in other galaxies and should aid with: (i) constructing (galaxy morphology)-dependent black hole mass functions; (ii) estimating the masses of black holes associated with tidal disruption events; (iii) better quantifying evolution in the scaling relations via improved comparisons with high-z data by alleviating the pickle of apples versus oranges; (iv) mergers and long-wavelength gravitational wave science; (v) simulations of galaxy/black hole coevolution and semi-analytic works involving galaxy speciation; plus (vi) facilitating improved extrapolations into the intermediate-mass black hole landscape. The role of the galaxy’s environment is also discussed, and many potential projects that can further explore the morphological divisions are mentioned.

Primordial black holes and dark matter mass spectra

Abstract Because primordial black holes (PBHs) evaporate into all particle species in nature, PBHs may emit several dark matter (DM) particle species with specific mass spectra. We assume that PBHs are the only source of DMs, and DMs only interact with the standard model particles gravitationally. We show a relation between the number of DM particle species NDM and initial PBH density β and mass $M_{\rm BH}^{\rm in}$. β–$M_{\rm BH}^{\rm in}$ curves for different NDM tend to overlap with each other for heavy initial PBHs. We also show the allowed region of DM masses for multiple DMs.

Truncated accretion discs in black hole X-ray binaries: dynamics and variability signatures

ABSTRACT Variable features in black hole X-ray binaries (BH-XRBs) are observed in different energy ranges and time-scales. The physical origin of different spectral states in BH-XRBs and their relations with the underlying accretion disc are still elusive. To investigate the intermediate state of BH-XRBs during outburst, we simulate a truncated accretion disc around a Kerr black hole using a general relativistic magnetohydrodynamical (GRMHD) framework under axisymmetry with adaptively refined mesh. Additionally, we have also carried out radiative transfer calculations for understanding the implications of disc dynamics on emission. Dynamically, the inner edge of the truncated accretion disc oscillates in a quasi-periodic fashion (QPO). The QPO frequency of oscillations (νQPO, max) increases as the magnetic field strength and magnetic resistivity increase. However, as the truncation radius increases, νQPO, max decreases. In our simulation models, frequency varies between $7\times (10\, {\rm M}_{\odot }/M_{\rm BH})$ Hz $\lesssim \nu _{\rm QPO, max}\lesssim 20 \times (10\, {\rm M}_{\odot }/M_{\rm BH})$ Hz, which is in the range of low-frequency QPOs. We further find evidence of transient shocks in the highly accreting stage during oscillation. Such a transient shock acts as an extended hot post-shock corona around the black hole that has an impact on its radiative properties. The radiative transfer calculations show signatures of these oscillations in the form of modulation in the edge-brightened structure of the accretion disc.

Large-scale outflow structure and radiation properties of super-Eddington flow: Dependence on the accretion rates

Abstract In order to evaluate the impacts made by super-Eddington accretors on their environments precisely, it is essential to guarantee a large enough simulation box and long computational time to avoid any artefacts from numerical settings as much as possible. In this paper, we carry out axisymmetric two-dimensional radiation hydrodynamic simulations around a 10 M⊙ black hole in large simulation boxes and study the large-scale outflow structure and radiation properties of super-Eddington accretion flow for a variety of black hole accretion rates, ${\dot{M}}_{\,\,\rm BH} = (110\!-\!380)L_{\rm Edd}/c^{\,\,2}$ (with LEdd being the Eddington luminosity and c being the speed of light). The Keplerian radius of the inflow material, at which centrifugal force balances with gravitational force, is fixed to 2430 Schwarzschild radii. We find that the mechanical luminosity grows more rapidly than the radiation luminosity with an increase of ${\dot{M}}_{\,\,\rm BH}$. When seen from a nearly face-on direction, especially, the isotropic mechanical luminosity grows in proportion to ${\dot{M}}_{\,\,\rm BH}^{\,\,2.7}$, while the total mechanical luminosity is proportional to ${\dot{M}}_{\,\,\rm BH}^{\,\,1.7}$. The reason for the former is that the higher ${\dot{M}}_{\,\,\rm BH}$ is, the more vertically inflated the disk surface becomes, which makes radiation fields more confined in the region around the rotation axis, thereby strongly accelerating outflowing gas. The outflow is classified into pure outflow and failed outflow, depending on whether the outflowing gas can reach the outer boundary of the simulation box or not. The fraction of the failed outflow decreases with a decrease of ${\dot{M}}_{\,\,\rm BH}$. We analyze physical quantities along each outflow trajectory, finding that the Bernoulli parameter (Be) is not a good indicator to discriminate between pure and failed outflows, since it is never constant because of continuous acceleration by radiation-pressure force. Pure outflow can arise, even if Be < 0 at the launching point.