Jongsuk Hong (KIAA) MODEST /06/28. Collaborators: E. Vesperini, A. Askar, M. Giersz, M. Szkudlarek & T. Bulik

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1 Jongsuk Hong (KIAA) MODEST /06/28 Collaborators: E. Vesperini, A. Askar, M. Giersz, M. Szkudlarek & T. Bulik

2 Introduction Method & models BBH mergers & Host cluster properties Merger rate estimation Summary 2

3 The FIRST detection -- GW Binary black hole (BBH) merger 5 BBH mergers, 1 BNS merger (EM counterpart) all compact binary mergers!! Formation mechanisms Isolated binary stellar evolution (e.g. Belczynski+2002,2007, 2018; Dominik+2012; Arca-Sedda & Benacquista 2018, ) Dynamical formation in dense stellar systems (e.g. Portegies Zwart & McMillan 2000; O Leary+2006; Rodriguez+2016; Samsing+2018, ) Relativistic capture (e.g. Quinlan & Shapiro 1987,1989; O Learly+2009; Hong & Lee 2015; Bae+2017; Gondan+2018, ), during 3-body encounters Orbital evolution of hierarchical systems (Aarseth 2012; Antonini+2014,2016; Arca- Sedda+2018; Rodriguez & Antonini 2018; Hoang+2018, ) Toonen s talk Environments (Kocsis s talk) Globular clusters (Banerjee+2010; Downing+2011; Tanikawa 2013; Bae+2014; Rodriguez+2015,2016; Askar+2017; Park+2017, ) Young/open clusters (Ziosi+2014; Banerjee+2017,2018, ) Rastello, Bamerjee s talks Galactic nuclei (O Leary+2009; Antonini & Perets 2012; Leigh+2018) Hoang s talk 3

4 Mass fallback prescription (Belczynski+2002; 2008) increase final masses and reduce natal kicks a significant number of BHs retained in stellar systems Black hole subsystem (BHS) affects the dynamical evolution of star clusters (e.g., Breen & Heggie 2013;Bae+2014) observational properties of host star clusters (Mackey+2008; Alessandrini+2016; Peuten+2016; Kremer+2018 Askar+2018; Arca-Sedda+2018; Li & Hong 2018) Dynamical evolution of BHS can produce BBHs. BBHs formed and ejected ~30% of dynamically escaping BHs are likely in binary systems (Morscher+2015;Park+2017) Breen & Heggie

5 Globular clusters mass (Morscher+2015; Rodriguez+2016; Askar+2017) Globular clusters size/spatial structure (Downing+2011; Morscher+2015; Rodriguez+2016; Askar+2017) Globular clusters velocity dispersion (Bae+2014; Park+2017) Metallicity (Belczynski+2010,2014; Downing+2011; Morscher+2015; Rodriguez+2016; Askar+2017; Giacobbo+2018) Fallback prescription (Belczynski+2002; Fryer+2012; Spera+2015; Chatterjee+2017, ) Stellar wind prescription (Belczynski+2010; Chatterjee+2017) Common-envelope evolution (Belczynski+2007; Belloni+2017) Binary fraction and distribution, initial mass function, (e.g.chatterjee+2017 and references) 5

6 MOCCA (Giersz+2008, 2013) code MOnte-Carlo Cluster simulator with FEWBODY (Fregeau+2004; Hypki & Giersz 2013) Initial mass function ( M sun ; Kroupa 2001) Stellar evolution (Single SE & Binary SE, Hurley et al. 2000; 2002) 162 models N = 1M, 500k, 200k Galactocentric distance: 4Kpc, 8Kpc, 16Kpc Half mass radius: 1pc, 2pc, 4pc Binary fraction: 10%, 20%, 50% Different binary distribution (standard / proto-binary evolution) Fixed metallicity Z = Tidal field, NS BH kicks (BH mass fallback) 6

7 Merger: escaping BBHs with T esc +T Peters <12Gyr 7

8 Merger: escaping BBHs with T esc +T Peters <12Gyr Dynamical BBH mergers: escape through dynamical interactions encounter, hardening, ejection rates, etc. Primordial BBH mergers: binary stellar evolution escape due to natal kicks initial binary fraction and distributions dynamical channel primordial channel 8

9 MOCCA-Survey data 1M direct N-body simulations 9

10 current 12,12 10

11 Merger rate decreases with time. (e.g. Downing+2011; Askar+2017; Fujii+2017) average rate over 12Gyr 11

12 chirp mass distribution depends on the metallicity (e.g. Giacobbo+2018) dynamical mergers more massive than primordial mergers dynamical mergers tend to have similar masses q~1 (Amaro-Seoane & Chen 2016; Rodriguez+2016; Park+2017) 12

13 Calculate the local merger rate density (Bulik+2004; Askar+2017) BBH merger contribution from individual GCs Askar+2017 Primordial BBH mergers GC formation history (Katz & Ricotti 2013) GC mass, number, age distribution Only related to the total mass in GCs local merger rate density: Gpc yr depending on the primordial binary fraction. (10%-100%) 13

14 need to reconstruct GCs size & mass distributions for dynamical mergers GC mass: Schechter (1976) function GC size: lognormal distributions ( ~0.4) with different large size distribution (Larsen 2004) small size distribution (Marks & Kroupa 2012) 14

15 need to reconstruct GCs size & mass distributions for dynamical mergers Local merger rate density w/ different GC distributions GC mass: Schechter (1976) function Gpc yr GC size: lognormal distributions ( ~0.4) with different large size distribution (Larsen 2004) small size distribution (Marks & Kroupa 2012) 15

16 Reproduce GGC distribution Mass distribution: Evolved Schechter function (Jordan+2007) A lognormal size distribution with different GC number density (Rodriguez+2016) Systematically lower than other studies (Rodriguez+2016; Askar+2017) Our GCMF covers GCs with lower mass and larger size. 16

17 Based on a survey of Monte-Carlo simulations of globular clusters, we obtained easy-to-use empirical relations for the production of binary black hole (BBH) mergers from globular clusters. We have classified two different origin of merging BBHs: primordial (binary stellar evolution) and dynamical (stellar encounter rate, binary hardening and escaping rates, ) BBH mergers. The expected number of merging BBHs from individual GCs can be expressed by using cluster initial mass, half-mass density and the binary fraction. We estimated the local merger rate density of Gpc yr for primordial BBH mergers and 1-20 Gpc yr for dynamical BBH mergers depending on the assumptions for the GC s mass and size distributions, and the GC formation rates and/or GC number density. 17