STOCHASTIC GRAVITATIONAL WAVE BACKGROUND FROM COALESCING BINARY BLACK HOLES

Abstract

We estimate the stochastic gravitational wave (GW) background signal from the\nfield population of coalescing binary stellar mass black holes (BHs) throughout\nthe Universe. This study is motivated by recent observations of BH-Wolf-Rayet\nstar systems and by new estimates in the metallicity abundances of star forming\ngalaxies that imply BH-BH systems are more common than previously assumed.\nUsing recent analytical results of the inspiral-merger-ringdown waveforms for\ncoalescing binary BH systems, we estimate the resulting stochastic GW\nbackground signal. Assuming average quantities for the single source energy\nemissions, we explore the parameter space of chirp mass and local rate density\nrequired for detection by advanced and third generation interferometric GW\ndetectors. For an average chirp mass of 8.7$M_{\\odot}$, we find that detection\nthrough 3 years of cross-correlation by two advanced detectors will require a\nrate density, $r_0 \\geq 0.5 \\rm{Mpc}^{-3} \\rm{Myr}^{-1}$. Combining data from\nmultiple pairs of detectors can reduce this limit by up to 40%. Investigating\nthe full parameter space we find that detection could be achieved at rates $r_0\n\\sim 0.1 \\rm{Mpc}^{-3} \\rm{Myr}^{-1}$ for populations of coalescing binary BH\nsystems with average chirp masses of $\\sim 15M_{\\odot}$ which are predicted by\nrecent studies of BH-Wolf-Rayet star systems. While this scenario is at the\nhigh end of theoretical estimates, cross-correlation of data by two Einstein\nTelescopes could detect this signal under the condition $r_0 \\geq 10^{-3}\n\\rm{Mpc}^{-3} \\rm{Myr}^{-1}$. Such a signal could potentially mask a primordial\nGW background signal of dimensionless energy density, $\\Omega_{\\rm{GW}}\\sim\n10^{-10}$, around the (1--500) Hz frequency range.\n