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    The formation of supermassive black holes (SMBHs) in the Universe and its role in the properties of the galaxies is one of the open questions in astrophysics and cosmology. Though, traditionally, electromagnetic waves have been instrumental in direct measurements of SMBHs, significantly influencing our comprehension of galaxy formation, gravitational waves (GW) bring an independent avenue to detect numerous binary SMBHs in the observable Universe in the nano-Hertz range using the pulsar timing array observation. This brings a new way to understand the connection between the formation of binary SMBHs and galaxy formation if we can connect theoretical models with multimessenger observations namely GW data and galaxy surveys. Along these lines, we present here the first paper on this series based on romulus25 cosmological simulation on the properties of the host galaxies of SMBHs and propose on how this can be used to connect with observations of nano-Hertz GW signal and galaxy surveys. We show that the most dominant contribution to the background will arise from sources with high chirp masses which are likely to reside in low-redshift early-type galaxies with high stellar mass, largely old stellar population, and low star formation rate, and that reside at centres of galaxy groups and manifest evidence of recent mergers. The masses of the sources show a correlation with the halo mass and stellar mass of the host galaxies. This theoretical study will help in understanding the host properties of the GW sources and can help in establishing a connection with observations.

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    Accurate measurement of the Hubble constant from standard sirens such as the gravitational wave (GW) sources with electromagnetic counterparts relies on the robust peculiar velocity correction of the redshift of the host galaxy. We show in this work that the peculiar velocity of the host galaxies exhibits a correlation with the properties of the host galaxy primarily such as its stellar mass and this correlation also evolves with redshift. As the galaxies of higher stellar mass tend to form in galaxies with higher halo masses which are located in spatial regions having a non-linear fluctuation in the density field of the matter distribution, the root mean square peculiar velocity of more massive galaxies is higher. As a result, depending on the formation channel of the binary compact objects, the peculiar velocity contamination to the galaxies will be different. The variation in the peculiar velocity of the host galaxies can lead to a significant variation in the estimation of the Hubble constant inferred using sources such as binary neutron stars. For the network of GW detectors such as LIGO-Virgo-KAGRA (LVK), LVK+LIGO-India, and Cosmic Explorer + Einstein Telescope, the variation in the precision of Hubble constant inferred from 10 bright siren events can vary from $\sim 5.4 - 6~{{\ \rm per \, cent}}$, $\sim 4.5 - 5.3~{{\ \rm per \, cent}}$, and $\sim 1.1 - 2.7~{{\ \rm per \, cent}}$, respectively. The impact of such a correlation between peculiar velocity and stellar mass on the inference of the Hubble constant is not only limited to GW sources but also applicable to type-Ia supernovae.

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  3. Abstract

    Using the novel semi-numerical code for reionization AMBER, we model the patchy kinetic Sunyaev–Zel’dovich (kSZ) effect by directly specifying the reionization history with the redshift midpointzmid, duration Δz, and asymmetryAz. We further control the ionizing sources and radiation through the minimum halo massMhand the radiation mean free pathλmfp. AMBER reproduces the free-electron number density and the patchy kSZ power spectrum of radiation–hydrodynamic simulations at the target resolution (1 Mpch−1) with matched reionization parameters. With a suite of (2 Gpc/h)3simulations using AMBER, we first constrain the redshift midpoint 6.0 <zmid< 8.9 using the Planck 2018 Thomson optical depth result (95% CL). Then, assumingzmid= 8, we find that the amplitude ofD=3000pkSZscales linearly with the duration of reionization Δzand is consistent with the 1σupper limit from South Pole Telescope (SPT) results up to Δz< 5.1 (Δzencloses 5%–95% ionization). Moreover, a shorterλmfpcan lead to a ∼10% lowerD=3000pkSZand a flatter slope in theD=3000pkSZΔzscaling relation, thereby affecting the constraints on Δzat= 3000. Allowingzmidandλmfpto vary simultaneously, we get spectra consistent with the SPT result (95% CL) up to Δz= 12.8 (butAz> 8 is needed to ensure the end of reionization beforez= 5.5). We show that constraints on the asymmetry require ∼0.1μk2measurement accuracy at multipoles other than= 3000. Finally, we find that the amplitude and shape of the kSZ spectrum are only weakly sensitive toMhunder a fixed reionization history and radiation mean free path.

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    An upper limit on the mass of a black hole set by the pair-instability supernovae (PISN) process can be useful in inferring the redshift of the gravitational wave (GW) sources by lifting the degeneracy between mass and redshift. However, for this technique to work, it is essential that the PISN mass scale is redshift independent or at least has a predictable redshift dependence. We show that the observed PISN mass scale can get smeared and the position of the PISN mass scale is likely to exhibit a strong redshift dependence due to a combined effect from the non-zero value of the delay time between the formation of a star and the merging of two black holes and the metallicity dependence of PISN mass scale. Due to the unknown form of the delay-time distribution, the redshift dependence of the PISN mass cutoff of the binary black holes (BBHs) cannot be well characterized and will exhibit a large variation with the change in redshift. As a result, the use of a fixed PISN mass scale to infer the redshift of the BBHs from the observed masses will be systematically biased. Though this uncertainty is not severe for the third observation run conducted by the LIGO–Virgo–KAGRA collaboration, in the future this uncertainty will cause a systematic error in the redshift inferred from the PISN mass scale. The corresponding systematic error will be a bottleneck in achieving a few per cent precision measurements of the cosmological parameters using this method in the future.

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    The measurement of the expansion history of the Universe from the redshift unknown gravitational wave (GW) sources (dark GW sources) detectable from the network of LIGO-Virgo-KAGRA (LVK) detectors depends on the synergy with the galaxy surveys having accurate redshift measurements over a broad redshift range, large sky coverage, and detectability of fainter galaxies.In this work, we explore the possible synergy of the LVK with the spectroscopic galaxy surveys, such as DESI and SPHEREx, to measure the cosmological parameters which are related to the cosmic expansion history and the GW bias parameters. We show that by using the 3D spatial cross-correlation between the dark GW sources and the spectroscopic galaxy samples, we can measure the value of Hubble constant with about $2{{\ \rm per\ cent}}$ and $1.5{{\ \rm per\ cent}}$ precision from LVK+DESI and LVK+SPHEREx, respectively within the 5 yr of observation time with $50{{\ \rm per\ cent}}$ duty-cycle. Similarly, the dark energy equation of state can be measured with about $10{{\ \rm per\ cent}}$ and $8{{\ \rm per\ cent}}$ precision from LVK+DESI and LVK+SPHEREx, respectively. We find that due to the large sky coverage of SPHEREx than DESI, performance in constraining the cosmological parameters is better from the former than the latter. By combining Euclid along with DESI and SPHEREx, a marginal gain in the measurability of the cosmological parameters is possible from the sources at high redshift (z ≥ 0.9).

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  6. Abstract We outline the “dark siren” galaxy catalog method for cosmological inference using gravitational wave (GW) standard sirens, clarifying some common misconceptions in the implementation of this method. When a confident transient electromagnetic counterpart to a GW event is unavailable, the identification of a unique host galaxy is in general challenging. Instead, as originally proposed by Schutz, one can consult a galaxy catalog and implement a dark siren statistical approach incorporating all potential host galaxies within the localization volume. Trott & Huterer recently claimed that this approach results in a biased estimate of the Hubble constant, H 0 , when implemented on mock data, even if optimistic assumptions are made. We demonstrate explicitly that, as previously shown by multiple independent groups, the dark siren statistical method leads to an unbiased posterior when the method is applied to the data correctly. We highlight common sources of error possible to make in the generation of mock data and implementation of the statistical framework, including the mismodeling of selection effects and inconsistent implementations of the Bayesian framework, which can lead to a spurious bias. 
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    Free, publicly-accessible full text available June 22, 2024

    Primordial black holes (PBHs) are dark matter candidates that span broad mass ranges from 10−17 M⊙ to ∼100 M⊙. We show that the stochastic gravitational wave background can be a powerful window for the detection of subsolar 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 subsolar mass PBHs ≤1 M⊙ in the form of dark matter $f_\mathrm{PBH}\le 1{{\ \rm per\ cent}}$ at $68{{\ \rm per\ cent}}$ C.L. even for a pessimistic value of a binary suppression factor. In the absence of any suppression of the merger rate, constraints on fPBH will be less than $0.001{{\ \rm per\ cent}}$. Furthermore, we will be able to measure the redshift evolution of the PBH merger rate with about $1{{\ \rm per\ cent}}$ accuracy, making it possible to uniquely distinguish between the Poisson and clustered PBH scenarios.

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  8. Abstract

    We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) searches for gamma-ray/X-ray counterparts to gravitational-wave (GW) candidate events identified during the third observing run of the Advanced LIGO and Advanced Virgo detectors. Using Fermi-GBM onboard triggers and subthreshold gamma-ray burst (GRB) candidates found in the Fermi-GBM ground analyses, the Targeted Search and the Untargeted Search, we investigate whether there are any coincident GRBs associated with the GWs. We also search the Swift-BAT rate data around the GW times to determine whether a GRB counterpart is present. No counterparts are found. Using both the Fermi-GBM Targeted Search and the Swift-BAT search, we calculate flux upper limits and present joint upper limits on the gamma-ray luminosity of each GW. Given these limits, we constrain theoretical models for the emission of gamma rays from binary black hole mergers.

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  9. Free, publicly-accessible full text available January 1, 2025