Revising natal kick prescriptions in population synthesis simulations

Nicola Giacobbo; Michela Mapelli

doi:10.3847/1538-4357/ab7335

paper

Revising natal kick prescriptions in population synthesis simulations

arXiv:1909.06385 · doi:10.3847/1538-4357/ab7335

Abstract

Natal kicks are matter of debate and significantly affect the merger rate density of compact objects. Here, we present a new simple formalism for natal kicks of neutron stars (NSs) and black holes (BHs). We describe the magnitude of the kick as $v_{kick} \propto f_{H05} m_{ej} m_{rem}^{- 1}$ , where $f_{H05}$ is a normalization factor, drawn from a Maxwellian distribution with one-dimensional root-mean-square velocity $σ = 265$ ~km~s $^{- 1}$ , $m_{ej}$ is the mass of the supernova (SN) ejecta and $m_{rem}$ is the mass of the compact object. This formalism matches the proper motions of young Galactic pulsars and can naturally account for the differences between core-collapse SNe of single stars, electron-capture SNe and ultra-stripped SNe occurring in interacting binaries. Finally, we use our new kick formalism to estimate the local merger rate density of binary NSs ( $R_{BNS}$ ), BH--NS binaries ( $R_{BHNS}$ ) and binary BHs ( $R_{BBH}$ ), based on the cosmic star formation rate density and metallicity evolution. In our fiducial model, we find $R_{BNS} \sim 600$ ~Gpc $^{- 3}$ ~yr $^{- 1}$ , $R_{BHNS} \sim 10$ ~Gpc $^{- 3}$ ~yr $^{- 1}$ and $R_{BBH} \sim 50$ ~Gpc $^{- 3}$ ~yr $^{- 1}$ , fairly consistent with the numbers inferred from the LIGO-Virgo collaboration.

arXiv comment13 pages, 5 figures, 2 table, ApJ, in press

Revising natal kick prescriptions in population synthesis simulations

Abstract

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