ACCRETION AND ORBITAL INSPIRAL IN GAS-ASSISTED SUPERMASSIVE BLACK HOLE BINARY MERGERS

ABSTRACT Gravitational waves from supermassive black hole binary mergers along with an electromagnetic counterpart have the potential to shed ‘light’ on the nature of dark energy in the intermediate redshift regime. Accurate measurement of dark energy parameters at intermediate redshift is extremely essential to improve our understanding of dark energy, and to possibly resolve a couple of tensions involving cosmological parameters. We present a Fisher matrix forecast analysis in the context of eLISA to predict the errors for three different cases: the non-interacting dark energy with constant and evolving equation of state (EoS), and the interacting dark sectors with a generalized parametrization. In all three cases, we perform the analysis for two separate formalisms, namely, the standard EoS formalism and the Om parametrization which is a model-independent null diagnostic for a wide range of fiducial values in both phantom and non-phantom regions, to make a comparative analysis between the prospects of these two diagnostics in eLISA. Our analysis reveals that it is wiser and more effective to probe the null diagnostic instead of the standard EoS parameters for any possible signature of dark energy at intermediate redshift measurements like eLISA.

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Constraining astrophysical observables of galaxy and supermassive black hole binary mergers using pulsar timing arrays

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1722 ◽

2019 ◽

Vol 488 (1) ◽

pp. 401-418 ◽

Cited By ~ 10

Author(s):

Siyuan Chen ◽

Alberto Sesana ◽

Christopher J Conselice

Keyword(s):

Black Hole ◽

Mass Function ◽

Host Galaxy ◽

Supermassive Black Hole ◽

Pulsar Timing ◽

Upper Limits ◽

Binary Mergers ◽

Black Hole Binary ◽

Merger Rate ◽

The Universe

ABSTRACT We present an analytic model to describe the supermassive black hole binary (SMBHB) merger rate in the Universe with astrophysical observables: galaxy stellar mass function, pair fraction, merger time-scale, and black hole–host galaxy relations. We construct observational priors and compute the allowed range of the characteristic spectrum hc of the gravitational wave background (GWB) to be 10−16 < hc < 10−15 at a frequency of f = 1 yr−1. We exploit our parametrization to tackle the problem of astrophysical inference from pulsar timing array (PTA) observations. We simulate a series of upper limits and detections and use a nested sampling algorithm to explore the parameter space. Corroborating previous results, we find that the current PTA non-detection does not place significant constraints on any observables; however, either future upper limits or detections will significantly enhance our knowledge of the SMBHB population. If a GWB is not detected at a level of hc(f = 1 yr−1) = 10−17, our current understanding of galaxy and SMBHB mergers is disfavoured at a 5σ level, indicating a combination of severe binary stalling, overestimating of the SMBH–host galaxy relations, and extreme dynamical properties of merging SMBHBs. Conversely, future detections of a Square Kilometre Array (SKA)-type instrument will allow to constrain the normalization of the SMBHB merger rate in the Universe, the time between galaxy pairing and SMBHB merging, the normalization of the SMBH–host galaxy relations and the dynamical binary properties, including their eccentricity and density of stellar environment.

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