Dark matter may consist, at least partially, of primordial black holes formed during the radiation-dominated era. The radiation produced by accretion onto primordial black holes leaves characteristic signatures on the properties of the medium at high redshift, before and after Hydrogen recombination. Therefore, reliable modelling of accretion onto these objects is required to obtain robust constraints on their abundance. We investigate the effect of mechanical feedback, i.e. the impact of outflows (winds and/or jets) on the medium, on primordial black hole accretion, and thereby on the associated radiation. Using analytical and numerical calculations, we study for the first time whether outflows can reduce the accretion rate of primordial black holes with masses similar to those detected by the LIGO-Virgo collaboration. Despite the complexity of the accretion rate evolution, mechanical feedback is able to significantly reduce the primordial black hole accretion rate, at least by an order of magnitude, when outflows are aligned with the motion of the compact object. If the outflow is perpendicular to the direction of motion, the effect is less important but still non-negligible. Outflows from primordial black holes, even rather weak ones, can significantly decrease the accretion rate, effectively weakening abundance constraints on these objects. Our results motivate further numerical simulations with a more realistic setup, which would yield more precise quantitative predictions.
The origin of the supermassive black holes that power the most distant quasars observed is largely unknown. One hypothesis is that they grew rapidly from intermediate-mass seeds (~100 M_sun) left by the first stars. However, some previous studies argued that accretion onto these black holes was too low to build up the mass due to strong suppression by radiative feedback. Here, we re-exam the accretion process of such a black hole embedded in a primordial gas cloud, by considering a wide range of physical and numerical parameters not explored before. We find that, while radiative heating and pr…
Primordial Black Holes evaporate due to Hawking radiation. We find that the evaporation time of primordial black holes increase when accretion of radiation is included.Thus depending on accretion efficiency more and more number of primordial black holes are existing today, which strengthens the idea that the primordial black holes are the proper candidate for dark matter.
We consider the effect of accretion of radiation in the early universe on primordial black holes in Brans-Dicke theory. The rate of growth of a primordial black hole due to accretion of radiation in Brans-Dicke theory is considerably smaller than the rate of growth of the cosmological horizon, thus making available sufficient radiation density for the black hole to accrete causally. We show that accretion of radiation by Brans-Dicke black holes overrides the effect of Hawking evaporation during the radiation dominated era. The subsequent evaporation of the black holes in later eras is further …
We consider the evolution of primordial black holes by including non-stationarity in their formation process and accretion of radiation in Brans-Dicke theory. Specifically, we focus on how $η$, the fraction of the horizon mass the black hole comprises capturing nonstationarity, affects the lifetimes of these primordial black holes. Our calculation reveals that the primordial black hole dynamics is controlled by the product $fη$ where $f$ is the accretion efficiency. We also estimate the impact of $η$ through $fη$ on the primordial black holes' initial mass fraction constraint obtained from the…
We consider the role of secondary infall and accretion onto an initially overdense perturbation in matter-dominated eras, like the one which is likely to follow the end of inflation. We show that primordial black holes may form through post-collapse accretion, namely the accretion onto an initial overdensity whose collapse has not given rise to a primordial black hole. Accretion may be also responsible for the growth of the primordial black hole masses by orders of magnitude till the end of the matter-dominated era.
We consider the constraints on the fraction of dark matter in the universe in the form of primordial black holes taking into account the crucial role of accretion which may change both their mass and mass function. We show that accretion may drastically weaken the constraints at the present epoch for primordial black holes with masses larger than a few solar masses.
We study the evolution of primordail black holes by considering present universe is no more matter dominated rather vacuum energy dominated. We also consider the accretion of radiation, matter and vacuum energy during respective dominance period. In this scenario, we found that radiation accretion efficiency should be less than 0.366 and accretion rate is much larger than previous analysis by B. Nayak et al. \cite{ns}. Thus here primordial black holes live longer than previous works \cite{ns}. Again matter accretion slightly increases the mass and lifetime of primordial black holes. However, t…
Should Primordial Black Holes (PBHs) exist in nature, they would inevitably accrete baryonic matter in their vicinity. In turn, the consequent emission of high-energy radiation could affect the thermal history of the universe to an extent that can be probed with a number of cosmological observables such as the Cosmic Microwave Background (CMB) anisotropies. However, our understanding of the accretion and radiation emission processes in the context of PBHs is still in its infancy, and very large theoretical uncertainties affect the resulting constraints on the PBH abundance. Building on state-o…
In this paper, we have investigated the processes of evaporation and accretion of primordial black holes during the radiation-dominated era and the matter-dominated era. This subject is very important since usually these two processes are considered independent of each other. In other words, previous works consider them in such a way that they do not have a direct effect on each other, and as a result, their effects on the mass of primordial black holes are calculated separately. The calculations of this paper indicate that assuming these two processes independently of each other will lead to …
Isolated stellar-mass BH accrete gas, often at supersonic speeds, and can form outflows that can influence the accreted gas. The latter process, known as mechanical feedback, can significantly affect the accretion rate. We use hydrodynamical simulations to assess the impact of mechanical feedback on the accretion rate when the BH moves supersonically through a uniform medium. We carry out 3D hydrodynamical simulations of outflows fueled by accretion that interact with a uniform medium, probing scales similar to and larger than the accretor gravitational sphere of influence. In the simulations …
Primordial black hole (PBH) dark matter (DM) nonlinear small-scale structure formation begins before the epoch of recombination due to large Poisson density fluctuations. Those small-scale effects still survive today, distinguishing physics of PBH DM structure formation from the one involving WIMP DM. We construct an analytic model for the small-scale PBH velocities that reproduces the velocity floor seen in numerical simulations, and investigate how these motions impact PBH accretion bounds at different redshifts. We find that the effect is small at the time of recombination, leaving the cosm…
We study the formation and long-term evolution of primordial protostellar disks harbored by first stars using numerical hydrodynamics simulations in the thin-disk limit. The initial conditions are specified by pre-stellar cores with distinct mass, angular momentum, and temperature. This allows us to probe several tens of thousand years of the disk's initial evolution, during which we observe multiple episodes of fragmentation leading to the formation of gravitationally bound gaseous clumps within spiral arms. These fragments are torqued inward due to gravitational interaction with the spiral a…
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…
Even if massive ($10\,M_\odot \lesssim M \lesssim 10^4 M_\odot$) primordial black holes (PBHs) can only account for a small fraction of the dark matter (DM) in the universe, they may still be responsible for a sizable fraction of the coalescence events measured by LIGO/Virgo, and/or act as progenitors of the supermassive black holes (SMBHs) observed already at high redshift ($z\gtrsim 6$). In presence of a dominant, non-PBH DM component, the bounds set by CMB via an altered ionization history are modified. We revisit the cosmological accretion of a DM halo around PBHs via toy models and dedica…
The first stars in the universe ionized the ambient primordial gas through various feedback processes. "Second-generation" primordial stars potentially form from this disturbed gas after its recombination. In this Letter, we study the late formation stage of such second-generation stars, where a large amount of gas accretes onto the protostar and the final stellar mass is determined when the accretion terminates. We directly compute the complex interplay between the accretion flow and stellar ultraviolet (UV) radiation, performing radiation-hydrodynamic simulations coupled with stellar evoluti…
We present coupled stellar evolution (SE) and 3D radiation-hydrodynamic (RHD) simulations of the evolution of primordial protostars, their immediate environment, and the dynamic accretion history under the influence of stellar ionizing and dissociating UV feedback. Our coupled SE-RHD calculations result in a wide diversity of final stellar masses covering 10 Msun $\lesssim M_* \lesssim$ 1000 Msun. The formation of very massive ($\gtrsim$ 250 Msun) stars is possible under weak UV feedback, whereas ordinary massive (a few x 10 Msun) stars form when UV feedback can efficiently halt the accretion.…
On the relative CNO underabundance in quasar absorption systems at $z \sim 3$ arising from Population III enrichment and attenuation by intermediate-mass black holes and primordial baryon accretion
National Institute for Space Research (INPE), Instituto Nacional de Pesquisas Espaciais（国家空间研究所）
Stellar-mass Primordial Black Holes (PBH) have been recently reconsidered as a Dark Matter (DM) candidate, after the aLIGO discovery of several binary BH mergers with masses of tens of $M_\odot$. Matter accretion on such massive objects leads to the emission of high-energy photons, capable of altering the ionization and thermal history of the universe. This in turn affects the statistical properties of the cosmic microwave background (CMB) anisotropies. Previous analyses have assumed spherical accretion. We argue that this approximation likely breaks down and that an accretion disk should form…
Supermassive stars (SMSs) forming via very rapid mass accretion (Mdot >~ 0.1 Msun/yr) could be precursors of supermassive black holes observed beyond redshift of about 6. Extending our previous work, we here study the evolution of primordial stars growing under such rapid mass accretion until the stellar mass reaches 10^{4 - 5} Msun. Our stellar evolution calculations show that a star becomes supermassive while passing through the "supergiant protostar" stage, whereby the star has a very bloated envelope and a contracting inner core. The stellar radius increases monotonically with the stellar …
The distribution of galaxies displays anisotropy on different scales and it is often referred as galaxy alignment. To understand the origin of galaxy alignments on small scales, one must investigate how galaxies were accreted in the early universe and quantify their primordial anisotropic at the time of accretion. In this paper we use N-body simulations to investigate the accretion of dark matter subhaloes, focusing on their alignment with the host halo shape and the orientation of mass distribution on large scale, defined using the hessian matrix of the density field. The large/small (e1/e3) …
In this paper, we consider the hypothesis that fractions of dark matter could be constituted by primordial black holes (PBHs). To test this possibility, we work out the observational properties of a static black hole embedded in the dark matter envelope made of a PBH source. The corresponding modifications of geometry due to such a physical system are investigated, with a particular focus on the accretion disk luminosity in spiral galaxies. The impact of the PBH presence is analyzed through modification of the disk luminosity and kinematic quantities. Thus, we discuss possible constraints on t…
We use the time-independent quantum-mechanical formulation of reactive collisions in order to investigate the state-to-state $\mathrm{H}^+ + \mathrm{HD} \to \mathrm{D}^+ + \mathrm{H}_2$ chemical reaction. We compute cross sections for collision energies up to 1.8 electron-volts and rate coefficients for temperatures up to 10000 kelvin. We consider HD in the lowest vibrational level $v=0$ and rotational levels $j=0$ to 4, and H$_2$ in vibrational levels $v'=0$ to 3 and rotational levels $j'=0$ to 9. For temperatures below 4000 kelvin, the rate coefficients strongly vary with the initial rotatio…
In this paper, we revisit the evaporation and accretion of primordial black holes (PBHs) during cosmic history and compare them to see if both of these processes are constantly active for PBHs or not. Our calculations indicate that during the radiation-dominated era, PBHs absorb ambient radiation due to accretion, and their apparent horizon grows rapidly. This growth causes the Hawking radiation process to practically fail and all the particles that escape as radiation from PBHs to fall back into them. Nevertheless, our emphasis is that the accretion efficiency factor also plays a very importa…
We consider cosmological evolution in Brans-Dicke theory with a population of primordial black holes. Hawking radiation from the primordial black holes impacts various astrophysical processes during the evolution of the Universe. The accretion of radiation by the black holes in the radiation dominated era may be effective in imparting them a longer lifetime. We present a detailed study of how this affects various standard astrophysical constraints coming from the evaporation of primordial black holes. We analyze constraints from the present density of the Universe, the present photon spectrum,…
It has recently been suggested that galaxies in the early Universe can grow through the accretion of cold gas, and that this may have been the main driver of star formation and stellar mass growth. Because the cold gas is essentially primordial, it has a very low abundance of elements heavier than helium (metallicity). As it is funneled to the centre of a galaxy, it will lead the central gas having an overall lower metallicity than gas further from the centre, because the gas further out has been enriched by supernovae and stellar winds, and not diluted by the primordial gas. Here we report ch…
Cold dark matter as the sum of different mass Primordial Black Holes (PBH) can explain a number of unsolved astrophysical mysteries. Here I assume a broad PBH mass distribution providing the bulk of the dark matter, consistent with all constraints and estimate the baryon accretion onto PBH contributing to cosmic background radiations, mainly the correlation signal between the Cosmic X-ray and the Cosmic infrared background fluctuations in deep Chandra and Spitzer surveys. I assume Bondi capture and advection dominated disk accretion with reasonable baryon densities and effective relative veloc…
Supermassive stars and quasi-stars (massive stars with a central black hole) are both considered as potential progenitors for the formation of supermassive black holes. They are expected to form from rapidly accreting protostars in massive primordial halos. We explore how long rapidly accreting protostars remain on the Hayashi track, implying large protostellar radii and weak accretion luminosity feedback. We assess the potential role of energy production in the nuclear core, and determine what regulates the evolution of such protostars into quasi-stars or supermassive stars. We follow the con…
Primordial black holes formed in an early post-inflation matter-dominated epoch during preheating provide a novel pathway for a source of the dark matter that utilizes known physics in combination with plausible speculations about the role of quantum gravity. Two cases are considered here: survival of Planck-scale relics and an early universe accretion scenario for formation of primordial black holes of asteroid-scale masses.
We revisit cosmic microwave background (CMB) constraints on primordial black hole dark matter. Spectral distortion limits from COBE/FIRAS do not impose a relevant constraint. Planck CMB anisotropy power spectra imply that primordial black holes with $m_{BH}\gtrsim 5~M_{\odot}$ are disfavored. However, this is susceptible to sizeable uncertainties due to the treatment of the black hole accretion process. These constraints are weaker than those quoted in earlier literature for the same observables.
In this study, we investigate the consequence of the constant-roll condition and examine the role of $f(Q,T)$ gravity in the cosmological inflation process. We analyze the inflationary scenario by calculating modified Friedmann equations, and giving an alternative technique that enables relating modified slow-roll parameters to the constant roll parameter $β$. Considering both chaotic and hilltop models, we calculate the spectral index and the tensor-to-scalar ratio and compare their compatibility with Planck's data for different choices of the constant roll parameter $β$. We examine the evolu…
Supermassive primordial stars are suspected to be the progenitors of the most massive quasars at z~6. Previous studies of such stars were either unable to resolve hydrodynamical timescales or considered stars in isolation, not in the extreme accretion flows in which they actually form. Therefore, they could not self-consistently predict their final masses at collapse, or those of the resulting supermassive black hole seeds, but rather invoked comparison to simple polytropic models. Here, we systematically examine the birth, evolution and collapse of accreting non-rotating supermassive stars un…
Much attention has been drawn to the recent discoveries by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) of merging intermediate mass black holes. Of particular interest is the possibility that the merger events detected could be evidence of dark matter in the form of primordial black holes (PBHs). It has been argued that the presence of many black holes would effect the thermal and ionization history of the universe via their accretion of matter which would have strong signatures in the Cosmic Microwave Background's (CMB) power spectra evident in the damping of aniso…
Magnetic fields are considered as a vital ingredient of contemporary star formation, and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations, and are subsequently amplified by the small-scale dynamo, leading to a strong tangled magnetic field. Here we explore how the magnetic field provided by the small-scale dynamo is further amplified via the $α-Ω$ dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typi…
(Abridged) Ultracompact Minihaloes (UCMHs), which formed by dark matter accretion onto primordial black holes (PBHs) or initial dark matter overdensity produced by the primordial density perturbation, provide a new type of compact dark matter structure to ionize and heat the IGM after matter-radiation equality z_eq, which is much earlier than the formation of the first cosmological dark halo structure and later first stars. We show that dark matter annihilation density contributed by UCMHs can totally dominated over the homogenous dark matter annihilation background even for a tiny UCMH abunda…
Primordial supermassive stars (SMSs) formed in atomic-cooling halos at z ~ 15 - 20 are leading candidates for the seeds of the first quasars. Past numerical studies of the evolution of SMSs have typically assumed constant accretion rates rather than the highly variable flows in which they form. We model the evolution of SMSs in the cosmological flows that create them using the Kepler stellar evolution and implicit hydrodynamics code. We find that they reach masses of 1 - 2 x $10^5 M_{\odot}$ before undergoing direct-collapse to black holes (DCBHs) during or at the end of their main-sequence hy…
The LIGO and Virgo Interferometers have so far provided 11 gravitational-wave (GW) observations of black-hole binaries. Similar detections are bound to become very frequent in the near future. With the current and upcoming wealth of data, it is possible to confront specific formation models with observations. We investigate here whether current data are compatible with the hypothesis that LIGO/Virgo black holes are of primordial origin. We compute in detail the mass and spin distributions of primordial black holes (PBHs), their merger rates, the stochastic background of unresolved coalescences…
In this work, we study the evolution of Primordial Black Holes within the context of Loop Quantum Gravity. First we calculate the scale factor and energy density of the universe for different cosmic era and then taking these as inputs we study evolution of primordial black holes. From our estimation it is found that accretion of radiation does not affect evolution of primordial black holes in loop quantum gravity even though a larger number of primordial black holes may form in early universe in comparison with Einstein's or scalar-tensor theories.
We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as T_{reh} <~ 10^2 MeV can magnetic fields of 10^{-15} G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic t…
The calculation results of the evolution of the cluster of primordial black holes based on the Fokker-Planck equation with neglecting of the gas accretion onto black holes are presented. In addition, we consider how a massive black hole located within the cluster center affects on its evolution. Despite it creates an additional potential in the central region of the cluster and might capture surrounding black holes, a negligible growth rate of a central black hole was shown for 1 Gyr. Furthermore, we find a significant (approximately tenfold) expansion of the cluster.
We examine unresolved nuclear X-ray sources in 57 brightest cluster galaxies to study the relationship between nuclear X-ray emission and accretion onto supermassive black holes (SMBHs). The majority of the clusters in our sample have prominent X-ray cavities embedded in the surrounding hot atmospheres, which we use to estimate mean jet power and average accretion rate onto the SMBHs over the past several hundred Myr. We find that ~50% of the sample have detectable nuclear X-ray emission. The nuclear X-ray luminosity is correlated with average accretion rate determined using X-ray cavities, wh…
The EDGES experiment has recently measured an anomalous global 21-cm spectrum due to hydrogen absorptions at redshifts of about $z\sim 17$. Model independently, the unusually low temperature of baryons probed by this observable sets strong constraints on any physical process that transfers energy into the baryonic environment at such redshifts. Here we make use of the 21-cm spectrum to derive bounds on the energy injection due to a possible population of ${\cal O}(1-100) M_\odot$ primordial black holes, which induce a wide spectrum of radiation during the accretion of the surrounding gas. Afte…
Primordial black holes as dark matter candidates: Multi-frequency constraints from cosmic radiation backgrounds
Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）；CONICET-Universidad Nacional de Córdoba（阿根廷国家科学研究委员会-科尔多瓦国立大学）；Universität Heidelberg（海德堡大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
Cosmological simulations of Population (Pop) III star formation suggest that the primordial initial mass function may have extended to sub-solar masses. If Pop III stars with masses < 0.8 M_Sun did form, then they should still be present in the Galaxy today as either main sequence or red giant stars. Despite broad searches, however, no primordial stars have yet been identified. It has long been recognized that the initial metal-free nature of primordial stars could be masked due to accretion of metal-enriched material from the interstellar medium (ISM). Here we point out that while gas accreti…
