Constraining population synthesis models via the binary neutron star population

Abstract

The observed sample of double neutron-star (NS-NS) binaries presents a challenge to population-synthesis models of compact object formation: the parameters entering into these models must be carefully chosen so as to match (i) the observed star formation rate and (ii) the formation rate of NS-NS binaries, which can be estimated from the observed sample and the selection effects related to the discoveries with radio-pulsar surveys. In this paper, we select from an extremely broad family of possible population synthesis models those few (2%) which are consistent with the observed sample of NS-NS binaries. To further sharpen the constraints the observed NS-NS population places upon our understanding of compact-object formation processes, we separate the observed NS-NS population into two channels: (i) merging NS-NS binaries, which will inspiral and merge through the action of gravitational waves within $10$ Gyr, and (ii) wide NS-NS binaries, consisting of all the rest. With the subset of astrophysically consistent models, we explore the implications for the rates at which double black hole (BH-BH), black hole-neutron star (BH-NS), and NS-NS binaries will merge through the emission of gravitational waves.Comment: (v1) Submitted to ApJ. Uses emulateapj.cls. 8 pages, 7 figures. (v2) Minor textual changes in response to referee queries. Substantial additions in appendicies, including a detailed discussion of sample multidimensional population synthesis fit