The Role Of Globular Clusters During Reionization

Transcription

1 The Role Of Globular Clusters During Reionization MKI Level 5, Room 582K

2 Collaboration University of Queensland University of Sussex University of Stockholm Michael Drinkwater Ilian Iliev Peter Thomas Garrelt Mellema

3 Outline Background What do we know about globular clusters and their formation? What is their relationship to reionization? Previous numerical work My Work Identify formation sites & modelling them as sources Take home message: Globular clusters are important contributors! Extensions: dynamical disruption Summary

4 Background

5 Globular Cluster Primer Dense stellar systems 10 kpc Consist of stars Very, very, very old ~ 13 Gyrs Located in bulge and halo Disk Bulge This room Milky Way N ~160

6 Globular Cluster Primer Two populations: metal-rich & metal-poor

7 Formation Scenarios Major Mergers Antennae Galaxies

8 Formation Scenarios t = 0 Hierarchical t = 13 Gyrs

9 Relation To Reionization Majority formed between ~10-14 Gyrs ago Forbes & Bridges (2010)

10 Relation To Reionization Age consistent with reionization epoch Metal Poor GC Formation Barkana & Loeb (2007)

11 Relation To Reionization Evidence that metal-poor GCs trace reionization epoch Number Density Spitler et al. (2012)

12 Relation To Reionization Potential to produce high numbers of ionising photons Schaerer & Charbonnel (2011)

13 Previous Work Modelled formation but not contribution to reionization Bekki et al. (2003, 2008) Kravtsov & Gnedin (2005) ~20 particles per GC sensitive to halo finder ~100 particles per GC only evolved to z = 3

14 My Work

15 The Aquarius Suite ~2000 particles per cluster

16 Identifying Formation Sites Cooling is most efficient at T~10 4 K Cooling Rate [erg cm^3/sec] molecular cooling atomic cooling Temperature [K] Loeb (2010)

17 Identifying Formation Sites Assuming dark matter is in equilibrium with the gas, we can use the velocity dispersion to infer a temperature. We tag all dark matter objects that go above this velocity dispersion threshold.

18 The Radiative Transfer Code

19 The Radiative Transfer Code Well tested against other codes

20 The Radiative Transfer Code Ray tracing naturally treats inhomogeneities correctly

21 Range Of Efficiencies Physically motivated from literature # photons per baryon star formation efficiency escape fraction --Tumlinson et al. (2004) --Baumgardt & Makino (2007) --Yajima et al. (2011) Ferrara & Loeb (2011) Wise & Cen (2009)

22 Photon-Poorest Photon-Richest

23 M1_512_ph150 M1_512_ph250 M1_512_ph500 M1_512_ph700 M1_512_ph1000 M1_512_ph5000 potential sources 60% suppression 85% suppression Results In-homgeneous Ionization Number redshift Griffen+ (2013)

24 Results 120 z = 0 radial distributions 100 Number M1_512_ph150 M1_512_ph250 M1_512_ph500 M1_512_ph700 M1_512_ph1000 M1_512_ph5000 truncated at z = 13 Milky Way GCs [Fe/H] < R/kpc Griffen+ (2013) Shallow when compared to Milky Way metal-poor GC distribution

25 z = 13 Results Contribution To Local Reionization z = 10 z = 7 x v f box width γ [h 1 Mpc] x v f box width γ [h 1 Mpc] x v f box width γ [h 1 Mpc] x m f box width γ [h 1 Mpc] x m f box width γ [h 1 Mpc] x m f box width γ [h 1 Mpc] Griffen+ (2013)

26 Results Contribution To Local Reionization (within 2 3 h -3 Mpc 3 ) Volume xfraction v redshift 10 M1_512_ph150 M1_512_ph250 M1_512_ph500 M1_512_ph700 M1_512_ph1000 M1_512_ph Mass Fraction x m redshift 10 M1_512_ph150 M1_512_ph250 M1_512_ph500 M1_512_ph700 M1_512_ph1000 M1_512_ph Griffen+ (2013)

27 Model Extensions Dynamical Disruption

28 Model Extensions Dynamical Disruption galactocentric radius scaling parameter orbital eccentricity mass of cluster galaxy rotation velocity Baumgardt & Makino (2003)

29 Results The effect of disruption Number R/kpc f (< R) R/kpc Griffen+ (2013) 60% of all primordial GCs are destroyed through dynamical disruption alone M1_512_ph150 surv. M1_512_ph150 total M1_512_ph250 surv. M1_512_ph250 total M1_512_ph500 surv. M1_512_ph500 total M1_512_ph700 surv. M1_512_ph700 total M1_512_ph1000 surv. M1_512_ph1000 total M1_512_ph5000 surv. M1_512_ph5000 total Milky Way GCs [Fe/H] < 1

30 Future Work Number Density Spitler et al. (2012) Millennium-II simulation

31 CaterPillar Project Being carried out on level 5/6 Team: Greg Dooley Alex Ji Phillip Zukin Anna Frebel Ed Bertschinger Parent Simulation 100 Mpc/h Status: Parent simulation complete Selecting 60+ Milky Way sized halos First halo at high resolution to be completed soon Avalanche of data to follow...

32 Summary Model Metal-poor globular clusters formed within small dark matter halos Age, stellar properties make them ideal candidates for reionization. Combined high-resolution dark matter simulation with radiative transfer. Take Home Message Metal-poor globular clusters are candidate contributors to reionization. MPGCs contributed ~50% of ionised mass and volume by z = 10. Improve: test against a variety environments + include baryons. Characterising their contributions is within reach of JWST.