Modest 15-s, Kobe, Japan Jongsuk Hong (Indiana University) & Enrico Vesperini, Antonio Sollima, Stephen McMillan, Franca D Antona, Annibale D Ercole

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1 Modest 15-s, Kobe, Japan Jongsuk Hong (Indiana University) & Enrico Vesperini, Antonio Sollima, Stephen McMillan, Franca D Antona, Annibale D Ercole 1

2 Introduction Introduction Initial conditions & Method Results Number evolution Binding energy Mixed binaries Radial distribution Link to the observations Summary (Hong et al. 2015, MNRAS, 449, 629; Hong et al. submitted to MNRAS) 2

3 Introduction Photometric (Lee et al. 1999; Bedin et al. 2004; Siegel et al. 2007; Piotto et al. 2007, 2015; Milone et al. 2008, 2010, 2012; Bellini et al. 2013) Main-sequence, turn-off, red giant branch, horizontal branch Spectroscopic (e.g., Carretta et al. 2009a,b; Gratton et al. 2012) Different chemical abundance Na-O, C-N anti-correlation SG FG Piotto et al Carretta et al

4 Introduction Origin of gas for second-generation/enriched population formation Massive stars Fast rotating stars (e.g., Prantzos & Charbonnel 2006; Decressin et al. 2007a) Binaries (e.g., de Mink et al. 2009, Bastian et al. 2013) AGB stars (e.g. Ventura et al. 2001) Supermassive star (e.g., Denissenkov & Hartwick 2014) 4

5 Introduction All formation models predicted that SG stars form in the central region of FG system (e.g., D Ercole et al. 2008) Number fraction of SG stars 47Tuc; Milone te al. 2012; Cordero et al SG-to-FG number ratio Lardo et al Radial distance Radial distance (see also e.g., Sollima et al. 2007; Bellini et al. 2009; Lardo et al. 2011; Milone et al. 2012; Beccari et al. 2013; Cordero et al. 2014; Kucinskas et al. 2014) complete spatial mixing only after significant mass loss (Vesperini et al. 2013, see also M. Miholics talk; see e.g., Milone et al. 2013; Dalessandro et al. 2014, for examples of mixed clusters) 5

6 Introduction HST-based proper motion studies: 47 Tuc, NGC2808 (Richer et al. 2013; Bellini et al. 2015). FG isotropic ; SG radially anisotropic Blue MS SG Red MS FG 47Tuc; Richer et al

7 Introduction Binary interactions are source of energy and support against core collapse (e.g., Henon 1961; Heggie & Hut 2003). Binary interactions produce many kinds of exotic objects (e.g., blue stragglers, low-mass X-ray binaries, millisecond pulsars, cataclysmic variables, etc.). (e.g., Clark 1975; Sarazin et al. 2003; Jordan et al. 2004; Pooley et al. 2003; Pooley & Hut 2006; Hui et al. 2010; Bahramian et al. 2013) 7

8 Introduction Binary interactions are source of energy and support against core collapse (e.g., Henon 1961; Heggie & Hut 2003). Binary interactions produce many kinds of exotic objects (e.g., blue stragglers, low-mass X-ray binaries, millisecond pulsars, cataclysmic variables, etc.). (e.g., Clark 1975; Sarazin et al. 2003; Jordan et al. 2004; Pooley et al. 2003; Pooley & Hut 2006; Hui et al. 2010; Bahramian et al. 2013) GOAL: investigate the dynamical evolution of binaries in multiple-population globular clusters, implications of the initial structural differences for the evolution and survival of FG and SG primordial binaries. 7

9 NBODY6+GPU (Nitadori & Aarseth 2012) SG stars form a compact subsystem compared to the FG stars (e.g., D Ercole et al. 2008). R h,fg /R h,sg =5, 10 M SG =M FG Binary fraction: 3%, 10% Binary hardness x g =E bin /<m>σ 2 Tidally truncated local hardness IU Big Red II Supercomputer 8

10 FG binaries Rapid decrease of SG binary number Preferential disruption and ejection of SG binaries SG binaries SG binaries are segregated in the cluster central regions where the rate of binary interactions leading to disruption and ejection is larger. 9

11 Binding energy evolution of surviving binaries more evident for inner (preferentially SG) binaries SG FG Hong et al

12 Binding energy evolution of surviving binaries more evident for inner (preferentially SG) binaries SG FG hardening disruption Hong et al

13 Binding energy evolution of surviving binaries more evident for inner (preferentially SG) binaries Number of binaries Binary binding energy 11

14 Binding energy evolution of surviving binaries more evident for inner (preferentially SG) binaries Number of binaries disruption hardening Binary binding energy 11

15 Mixed binaries : binaries with one FG and one SG stars (from Davies 2014) Maximum number of mixed binaries No mixed binary produced Initial hardness No mixed binary retained 12

16 Mixed binaries : binaries with one FG and one SG stars (from Davies 2014) Softer binaries : larger interaction rates, disruption Maximum number of mixed binaries No mixed binary produced Initial hardness No mixed binary retained 12

17 Mixed binaries : binaries with one FG and one SG stars (from Davies 2014) Softer binaries : larger interaction rates, disruption Maximum number of mixed binaries Harder binaries : smaller interaction rates, ejection No mixed binary produced Initial hardness No mixed binary retained 12

18 Radial profile of the binary fraction is the result of the combined effect of binary segregation, disruption and ejection. Binary fraction disruption & ejection segregation Radial distance 13

19 Radial profile of the binary fraction is the result of the combined effect of binary segregation, disruption and ejection. Binary fraction disruption & ejection segregation ~30R c Milone et al (arxiv: ) Radial distance 13

20 Time Evolution of radial profile driven by the interplay between disruption/ejection of SG binaries, and segregation of FG binaries FG binary segregation SG binary disruption & ejection SG-to-FG number ratio global ratio decreases due to preferential disruption and ejection of SG binaries Radial distance 14

21 Binary fraction for each population f b,fg =N b,fg /(N b,fg +N s,fg ) f b,sg =N b,sg /(N b,sg +N s,sg ) 15

22 Binary fraction for each population f b,fg =N b,fg /(N b,fg +N s,fg ) f b,sg =N b,sg /(N b,sg +N s,sg ) Qualitatively consistent with the trend of observations by Lucatello et al VLT observations ~1000 RGB stars at ~ R h in 10 galactic GCs larger binary fraction for FG (~5%) than SG (~1%) 15

23 Differences in the structural properties of the SG and FG populations: SG more centrally concentrated in the cluster inner regions. SG binaries are more affected by dynamical processes Preferential disruption (softer binaries) and ejection (harder binaries) of SG binaries. Binding energy distribution of SG surviving binaries more affected by dynamics than FG binaries. Global SG binary fraction smaller than FG binary fraction. consistent with first observational studies. Exchange encounters formation of mixed (SG+FG) binaries. Radial distribution of binaries driven by the interplay among binary segregation, disruption, and ejection. ) (More details in Hong et al. 2015, MNRAS, 449, 629; Hong et al. submitted to MNRAS) 16