New insights on binary black hole formation channels after GWTC-2: young star clusters versus isolated binaries
| Autor: | Ugo N. Di Carlo, M. Celeste Artale, Nicola Giacobbo, Giuliano Iorio, Yann Bouffanais, Filippo Santoliquido, Sara Rastello, Michela Mapelli |
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| Rok vydání: | 2021 |
| Předmět: |
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics education.field_of_study Metallicity Population FOS: Physical sciences Sigma Astronomy and Astrophysics Field (mathematics) Astrophysics 01 natural sciences Distribution (mathematics) Binary black hole Mixing (mathematics) Space and Planetary Science 0103 physical sciences Astrophysics - High Energy Astrophysical Phenomena 010306 general physics education 010303 astronomy & astrophysics Spin-½ |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 507:5224-5235 |
| ISSN: | 1365-2966 0035-8711 |
| Popis: | With the recent release of the second gravitational-wave transient catalogue (GWTC-2), which introduced dozens of new detections, we are at a turning point of gravitational wave astronomy, as we are now able to directly infer constraints on the astrophysical population of compact objects. Here, we tackle the burning issue of understanding the origin of binary black hole (BBH) mergers. To this effect, we make use of state-of-the-art population synthesis and N-body simulations, to represent two distinct formation channels: BBHs formed in the field (isolated channel) and in young star clusters (dynamical channel). We then use a Bayesian hierarchical approach to infer the distribution of the mixing fraction $f$, with $f=0$ ($f=1$) in the pure dynamical (isolated) channel. %that controls the proportion of isolated and dynamical BBHs. We explore the effects of additional hyper-parameters of the model, such as the spread in metallicity $\sigma_{\text{Z}}$ and the parameter $\sigma_{\text{sp}}$, describing the distribution of spin magnitudes. We find that the dynamical model is slightly favoured with a median value of $f=0.26$, when $\sigma_{\text{sp}}=0.1$ and $\sigma_{\text{Z}}=0.4$. Models with higher spin magnitudes tend to strongly favour dynamically formed BBHs ($f\le{}0.1$ if $\sigma_{\text{sp}}=0.3$). Furthermore, we show that hyper-parameters controlling the rates of the model, such as $\sigma_{\rm Z}$, have a large impact on the inference of the mixing fraction, which rises from $0.18$ to $0.43$ when we increase $\sigma_{\text{Z}}$ from 0.2 to 0.6, for a fixed value of $\sigma_{\text{sp}}=0.1$. Finally, our current set of observations is better described by a combination of both formation channels, as a pure dynamical scenario is excluded at the $99\%$ credible interval, except when the spin magnitude is high. Comment: 13 pages, 10 figures, 2 tables, published in MNRAS |
| Databáze: | OpenAIRE |
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