The effect of the metallicity-specific star formation history on double compact object mergers

Abstract

We investigate the impact of uncertainty in the metallicity-specific star formation rate over cosmic time on predictions of the rates and masses of double compact object mergers observable through gravitational waves. We find that this uncertainty can change the predicted detectable merger rate by more than an order of magnitude, comparable to contributions from uncertain physical assumptions regarding binary evolution, such as mass transfer efficiency or supernova kicks. We statistically compare the results produced by the COMPAS population synthesis suite against a catalog of gravitational-wave detections from the first two Advanced LIGO and Virgo observing runs. We find that the rate and chirp mass of observed binary black hole mergers can be well matched under our default evolutionary model with a star formation metallicity spread of 0.39 dex around a mean metallicity Z that scales with redshift z as Z = 0.035×10 −0.23z , assuming a star formation rate of 0.01×(1+z) 2.77 /(1+((1+ z)/2.9) 4.7 ) M Mpc −3 yr −1 . Intriguingly, this default model predicts that 80% of the approximately one binary black hole merger per day that will be detectable at design sensitivity will have formed through isolated binary evolution with only dynamically stable mass transfer, i.e., without experiencing a common-envelope event.

Modelling double neutron stars: radio and gravitational waves

“…Stevenson et al 2017;Barrett et al 2018;Stevenson et al 2019;Bavera et al 2019) or a NS (e.g. Vigna-Gómez et al 2018;Neijssel et al 2019;Broekgaarden et al 2019), but did not follow any subsequent evolution of these objects. To analyse whether a NS is also a pulsar, other properties such as the magnetic field and spin period need to assigned to the NS and calculated over time, e.g.…”

“…The metallicity is kept constant across all models to solar metallicity, Z = 0.0142 (Asplund et al 2009), which is a justified assumption since we focus on Milky Way field DNS systems. Additionally Neijssel et al (2019) showed that Table 2. Description of models used in this paper.…”

Mind the Gap: The Location of the Lower Edge of the Pair-instability Supernova Black Hole Mass Gap

“…Therefore, even if it is possible to determine the host galaxy despite the limited spatial localization of binary BH mergers, the local observed population of stars may have formed later and hence have a different metallicity to that of the BH progenitor. This complicates estimating the rate of BH formation (Portegies Zwart & McMillan 2000;Dominik et al 2012;Abbott et al 2016b), since this estimate requires knowing the star formation rate and metallicity evolution of the universe (Madau & Dickinson 2014;Mapelli et al 2019;Neijssel et al 2019).…”

Detecting double neutron stars with LISA

“…In this paper, we predict the detection rate, distribution of source parameters (eccentricity, signal-to-noise ratio, distance), and uncertainty in source parameters (eccentricity uncertainty, sky-localisation accuracy, chirp mass uncertainty) of DNSs in the Milky Way (MW) and in nearby galaxies. We generate a population of synthetic DNSs using the Compact Object Mergers: Population Astrophysics and Statistics (COMPAS) suite (Stevenson et al 2017;Barrett et al 2018;Neijssel et al 2019), and follow the evolution of these DNSs through the LISA band driven by gravitational radiation reaction, for which we use the leading quadrupole order expressions (Peters 1964). Starting from an initial population of zero-age main sequence (ZAMS) binary stars, COMPAS performs single-star evolution using the fitting formulae in Hurley et al (2000) and calculates changes in stellar and orbital properties due to wind-driven mass loss, mass transfer, common-envelope events, and SNe, until the formation of a DCO.…”