Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStochastic gravitational-wave background as a tool to investigate multi-channel astrophysical and primordial black-hole mergers
193
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The formation of merging binary black holes can occur through multiple astrophysical channels such as, e.g., isolated binary evolution and dynamical formation or, alternatively, have a primordial origin. Increasingly large gravitational-wave catalogs of binary black-hole mergers have allowed for the first model selection studies between different theoretical predictions to constrain some of their model uncertainties and branching ratios. In this work, we show how one could add an additional and independent constraint to model selection by using the stochastic gravitational-wave background. In contrast to model selection analyses that have discriminating power only up to the gravitational-wave detector horizons (currently at redshifts $zlesssim 1$ for LIGO-Virgo), the stochastic gravitational-wave background accounts for the redshift integration of all gravitational-wave signals in the Universe. As a working example, we consider the branching ratio results from a model selection study that includes potential contribution from astrophysical and primordial channels. We renormalize the relative contribution of each channel to the detected event rate to compute the total stochastic gravitational-wave background energy density. The predicted amplitude lies below the current observational upper limits of GWTC-2 by LIGO-Virgo, indicating that the results of the model selection analysis are not ruled out by current background limits. Furthermore, given the set of population models and inferred branching ratios, we find that, even though the predicted background will not be detectable by current generation gravitational-wave detectors, it will be accessible by third-generation detectors such as the Einstein Telescope and space-based detectors such as LISA.
rate research
Read More
We use population inference to explore the impact that uncertainties in the distribution of binary black holes (BBH) have on the astrophysical gravitational-wave background (AGWB). Our results show that the AGWB monopole is sensitive to the nature of the BBH population (particularly the local merger rate), while the anisotropic $C_ell$ spectrum is only modified to within a few percent, at a level which is insignificant compared to other sources of uncertainty (such as cosmic variance). This is very promising news for future observational studies of the AGWB, as it shows that (i) the monopole can be used as a new probe of the population of compact objects throughout cosmic history, complementary to direct observations by LIGO and Virgo and (ii) we are able to make surprisingly robust predictions for the $C_ell$ spectrum, even with only very approximate knowledge of the black hole population. As a result, the AGWB anisotropies have enormous potential as a new probe of the large-scale structure of the Universe, and of late-Universe cosmology in general.
The black hole merging rates inferred after the gravitational-wave detection by Advanced LIGO/VIRGO and the relatively high mass of the progenitors are consistent with models of dark matter made of massive primordial black holes (PBH). PBH binaries emit gravitational waves in a broad range of frequencies that will be probed by future space interferometers (LISA) and pulsar timing arrays (PTA). The amplitude of the stochastic gravitational-wave background expected for PBH dark matter is calculated taking into account various effects such as initial eccentricity of binaries, PBH velocities, mass distribution and clustering. It allows a detection by the LISA space interferometer, and possibly by the PTA of the SKA radio-telescope. Interestingly, one can distinguish this background from the one of non-primordial massive binaries through a specific frequency dependence, resulting from the maximal impact parameter of binaries formed by PBH capture, depending on the PBH velocity distribution and their clustering properties. Moreover, we find that the gravitational wave spectrum is boosted by the width of PBH mass distribution, compared with that of the monochromatic spectrum. The current PTA constraints already rule out broad-mass PBH models covering more than three decades of masses, but evading the microlensing and CMB constraints due to clustering.
Primordial black holes (PBHs) are dark matter candidates that span broad mass ranges from $10^{-17}$ $M_odot$ to $sim 100$ $M_odot$. We show that the stochastic gravitational wave background can be a powerful window for the detection of sub-solar mass PBHs and shed light on their formation channel via third-generation gravitational wave detectors such as Cosmic Explorer and the Einstein Telescope. By using the mass distribution of the compact objects and the redshift evolution of the merger rates, we can distinguish astrophysical sources from PBHs and will be able to constrain the fraction of sub-solar mass PBHs $leq 1$ $M_odot$ in the form of dark matter $f_{PBH}leq 1%$ at $68%$ C.L. even for a pessimistic value of the suppression factor ($f_{sup} sim 10^{-3}$). For $f_{sup} sim 1$, the constraints on $f_{PBH}$ will be less than $0.001%$. Furthermore, we will be able to measure the redshift evolution of the PBH merger rate with about $1%$ accuracy, making it possible to uniquely distinguish between the Poisson and clustered PBH scenarios.
We calculate the noise induced in the anisotropies of the astrophysical gravitational-wave background by finite sampling of both the galaxy distribution and the compact binary coalescence event rate. This shot noise leads to a scale-invariant bias term in the angular power spectrum $C_ell$, for which we derive a simple analytical expression. We find that this bias dominates over the true cosmological power spectrum in any reasonable observing scenario, and that only with very long observing times and removal of a large number of foreground sources can the true power spectrum be recovered.
We investigate the formation and growth of massive black hole (BH) seeds in dusty star-forming galaxies, relying and extending the framework proposed by Boco et al. 2020. Specifically, the latter envisages the migration of stellar compact remnants (neutron stars and stellar-mass black holes) via gaseous dynamical friction towards the galaxy nuclear region, and their subsequent merging to grow a massive central BH seed. In this paper we add two relevant ingredients: (i) we include primordial BHs, that could constitute a fraction $f_{rm pBH}$ of the dark matter, as an additional component participating in the seed growth; (ii) we predict the stochastic gravitational wave background originated during the seed growth, both from stellar compact remnant and from primordial BH mergers. We find that the latter events contribute most to the initial growth of the central seed during a timescale of $10^6-10^7,rm yr$, before stellar compact remnant mergers and gas accretion take over. In addition, if the fraction of primordial BHs $f_{rm pBH}$ is large enough, gravitational waves emitted by their mergers in the nuclear galactic regions could be detected by future interferometers like Einsten Telescope, DECIGO and LISA. As for the associated stochastic gravitational wave background, we predict that it extends over the wide frequency band $10^{-6}lesssim f [{rm Hz}]lesssim 10$, which is very different from the typical range originated by mergers of isolated binary compact objects. On the one hand, the detection of such a background could be a smoking gun to test the proposed seed growth mechanism; on the other hand, it constitutes a relevant contaminant from astrophysical sources to be characterized and subtracted, in the challenging search for a primordial background of cosmological origin.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
