Improved Modeling of Highly Eccentric EMRI Signal Confusion Noise for LISA

Scattering events around a supermassive black hole (SMBH) will occasionally toss a stellar-mass compact object into an orbit around the SMBH, beginning what is known as an extreme mass ratio inspiral (EMRI). The early stages of such a highly eccentric EMRI will not produce detectable gravitational waves because the source will only be in a suitable frequency band briefly (close to peribothron) during each long-period orbit. However, if we consider an ensemble of such subthreshold sources, spread across the Universe, together they produce an unresolvable background noise that may obscure sources otherwise detectable by LISA, the proposed space-based gravitational wave detector. Previous studies of this EMRI signal confusion background noise used a Newtonian order approximation. We seek to improve this characterization by implementing numerical kludge waveforms from relativistic population models. The waveforms were developed by a semi-relativistic code and are fully evolved inspirals from capture to the separatrix with the intent of fully exploring the orbital space. We will be tracking the evolution of the black hole population from a redshift of z=0 to z~3 using the Illustris Project. This information will be combined with an estimate of the number of mergers of compact objects with the black holes per unit volume to estimate the number of events contributing to the signal confusion noise.