Population synthesis with dynamics Natasha Ivanova MODEST-6 August 2005 or the problems that we face

What is population synthesis? Evolutionary Population Synthesis is the method of direct modeling of large populations of non-interacting objects (single or binaries in our case) with non-trivial (non- describable by simple analytic) evolution. Evolutionary Population Synthesis is the method of direct modeling of large populations of non-interacting objects (single or binaries in our case) with non-trivial (non- describable by simple analytic) evolution. The evolution for an object is followed from its birth till the desired moment. The goals: a) to see how the population looks like from statistical point of view b) to check if theory works OK and produces the same number of rare objects as observed c) predict new objects!

Collision time  coll : time between two successive collisions,  coll = 1/n c  S Collision time  coll : time between two successive collisions,  coll = 1/n c  S Hardness  : ratio between binary binding energy and kinetic energy of an average object Hardness  : ratio between binary binding energy and kinetic energy of an average object Soft binaries  <1 : get softer (Heggie 1975); very likely to be destroyed through ionization Soft binaries  <1 : get softer (Heggie 1975); very likely to be destroyed through ionization Hard binaries  >1 : get harder; the encounter can result in the exchange of the companion (smaller mass component is replaced by more massive intruder); very hard binary is likely to merge (Fregeau et al. 2004) Hard binaries  >1 : get harder; the encounter can result in the exchange of the companion (smaller mass component is replaced by more massive intruder); very hard binary is likely to merge (Fregeau et al. 2004) Basics of the binary dynamics

Why do we care about binaries? Interacted and destroyed binaries

Interacted and survived binaries

Non-Interacted binaries Among stars with the initial masses > 0.6 Msun only 8% only 8% are both hard and did not have interactions…

Magnetic braking Magnetic braking Mass transfer events Mass transfer events Mergers Mergers Common envelope events Common envelope events Tidal circularization and synchronization Tidal circularization and synchronization Accretion on WDs, Ia SN and subCh Ia Accretion on WDs, Ia SN and subCh Ia SN kicks and NS-retention: e-c SN? SN kicks and NS-retention: e-c SN? Triples?! Triples?! What do we NEED to take into account for binaries and why life is uncertain

IMF IMF Mass ratio distribution? Mass ratio distribution? How to pick the secondary? How to pick the secondary? Does q depend on the primary masses? Does q depend on the primary masses? Does q depend on binary periods? Does q depend on binary periods? What is about “twins”? What is about “twins”? Periods distribution? Periods distribution? Eccentricities distribution? Eccentricities distribution? Initial binaries/triples/quadruples/quintuples and sextuples fractions? Initial binaries/triples/quadruples/quintuples and sextuples fractions? A few spices before you start to boil the soup

Moscow (Yungleson, Tutukov, Lipunov, Postnov,…) Moscow (Yungleson, Tutukov, Lipunov, Postnov,…) Seba (Portegiez Zwart, Tout, Verbunt,…) Seba (Portegiez Zwart, Tout, Verbunt,…) SSE & BSE (Hurley, Pols, Tout) SSE & BSE (Hurley, Pols, Tout) Kalogera, Belczynski Kalogera, Belczynski Willems, Kolb Willems, Kolb … Brussel code (Vanbeveren & C o ): interpolation between tracks for massive stars Brussel code (Vanbeveren & C o ): interpolation between tracks for massive stars Podsiadlowski, Rappaport, Pfahl & Han : detailed binary tracks for specific classes of systems (Ia SN, LMXBs, sdB …) Podsiadlowski, Rappaport, Pfahl & Han : detailed binary tracks for specific classes of systems (Ia SN, LMXBs, sdB …) Some currently existing Population Synthesis codes for interacting binaries

ofast and robust ocorrect and powerful (not restricted to a certain class of objects) Time-scale: < one month on a modest 32-CPUs cluster (at 50% Memory-resources: 4Gb of memory (NO swapping!) 250,000 Msun GC: ~ 1,000,000 stars: < 40 seconds per star one star should not take more than 40kb in memory. An unavoidable fact: the evolution of a single star takes much less than the evolution of a binary, if one speaks about an interacting binary. So the code is better be able to evolve a single star on a time-scale of few seconds. Any wishes?

SS encounters SS encounters Mergers in physical collisions Mergers in physical collisions Binary formations via physical collisions Binary formations via physical collisions Binary formations via tidal captures Binary formations via tidal captures Three and four body encounters Three and four body encounters MT is interrupted MT is interrupted Eccentricity is changed Eccentricity is changed Exchange occurred and companions are now misaligned and not any more on the corotation Exchange occurred and companions are now misaligned and not any more on the corotation (multiple) physical collisions, including “dynamical” CE (multiple) physical collisions, including “dynamical” CE triples formation triples formation GC: evolution is perturbed!

How to deal with all the mess? Learn binary evolution in the field Learn binary evolution in the field Build a “scenario processor” for all events Build a “scenario processor” for all events Analyze what happens - does it make any sense? Analyze what happens - does it make any sense? Treat specific circumstances with great details Treat specific circumstances with great details Re-run Re-run Run to observers Run to observers Get from observers their results and sit for a while thinking why there is no common language Get from observers their results and sit for a while thinking why there is no common language

Formation of CV binaries: CE or encounter? Field, non-eccentric binaries

CVs formation: main formation channels MS-MS CV single binary BS/BB SS Destr Collis Exch CE Merger Coll RG Exch CE 10% 40% 15% 35%

CVs: population of WDs Field “Typical” cluster

Simulaions vs observations Simulations Observations

PS and dynamics: some currently active codes Hurley - open clusters, M67. Hurley - open clusters, M67. SeBa - IMBH formation, open clusters ecology SeBa - IMBH formation, open clusters ecology Brussel - young clusters with massive stars Brussel - young clusters with massive stars Freitag - IMBH formation, Galactic center Freitag - IMBH formation, Galactic center Fregeau, Gurkan, Rasio - IMBH formation, mass segregation in globular clusters with full IMF Fregeau, Gurkan, Rasio - IMBH formation, mass segregation in globular clusters with full IMF Ivanova, Belczynski, Fregeau, Rasio - binary fractions, compact binaries formation and evolution in globular clusters Ivanova, Belczynski, Fregeau, Rasio - binary fractions, compact binaries formation and evolution in globular clusters Postnov - NS retention, MSPs Postnov - NS retention, MSPs

Future of PS codes with dynamics Bill Paxton’s “EZ” code (Eggleton-refasted): one minute per single star one minute per single star Saul Rappaport and his students at MIT: large population study of binary evolution and RLO. Saul Rappaport and his students at MIT: large population study of binary evolution and RLO. 30,000 binaries in 24 hours at 35 nodes 30,000 binaries in 24 hours at 35 nodes (~2 minutes/RLO binary!!!) (~2 minutes/RLO binary!!!)