Modeling the Physics of Galaxy Formation

1. Modeling the Physics ofGalaxy Formation Andrew Benson California Institute of Technology

2. Scientific classification • Theorist • Scale • Galactic – cosmological • Wavelength range • Zero – infinity • Favorite color • Dark matter

3. Modeling the Physics of Galaxy Formation Overview Overview | Models | Science | Collaboration • Questions I'm interested in..... • How to build a coherent picture of galaxy formation • From the smallest scales to the largest • From low-z to high-z • Encompassing widest range of predictions/observations possible • First need a coherent framework for calculating expectations

4. Modeling the Physics of Galaxy Formation GALACTICUSsites.google.com/site/galacticusmodel Advancing Galaxy Formation Codes Overview | Models | Science | Collaboration • Why a new code? • Adding in new features (e.g. self-consistent reionization, noninstantaneous recycling, new star formation rules) to existing models can be challenging • How? • Create a code which is modular by design, isolating assumptions so that they don't have consequences throughout the code.

5. Modeling the Physics of Galaxy Formation Design Features Overview | Models | Science | Collaboration • Open source (compiles with GNU compilers) • Modular design • Each function can have multiple implementations, selected by input parameter. • “Node” can have arbitrary number of components (e.g. DM halo, disk, spheroid), all with multiple implementations • Combination of smooth (ODE) evolution and instantaneous events (e.g. mergers)

6. Modeling the Physics of Galaxy Formation Source codeBinariesCloud (Amazon EC2) Design Features Overview | Models | Science | Collaboration • Well documented • Promotes a standard format for merger tree data • www.ctcp.caltech.edu/galacticus/MergerTreeFileFormat.pdf • Parallelized • OpenMP • MPI (soon...) • Currently simple, but allows for expansion

7. Modeling the Physics of Galaxy Formation External Tools Overview | Models | Science | Collaboration • GNU Scientific Library/FGSL • ODE solver; integration; other numerics • FoX library • Read/write XML files • FSPS • Population synthesis • Cloudy • Cooling times

8. Modeling the Physics of Galaxy Formation Modularity Overview | Models | Science | Collaboration • New implementation of function easily added: • Write a module containing the function • Add directives indicating that this function is for, e.g., disk star formation timescale calculations • Recompile – build system automatically finds this new module and works out how to compile it into the code • Modules are self-contained and independent • Self-initializing and recursive

9. Modeling the Physics of Galaxy Formation Current Feature List Overview | Models | Science | Collaboration • Components • DM profile [isothermal/NFW] • Hot halo • Disk [exponential] • Spheroid [Hernquist] • Black holes Tracks mass and spin. Spin from mergers and accretion. Accretion spin-up using Benson & Babul formula Jet power from Benson & Babul also.

10. Modeling the Physics of Galaxy Formation Current Feature List Overview | Models | Science | Collaboration • Physics • Monte-Carlo (PCH method)/N-body merger trees • CIE atomic cooling • Dynamical friction • Star formation/feedback • Galaxy merging • Adiabatic contraction/sizes • Chemical enrichment (instant or non-instant)

11. Modeling the Physics of Galaxy Formation Current Feature List Overview | Models | Science | Collaboration • Physics (cont.): • Disk instabilities • Black hole merging • AGN feedback • Stellar population synthesis (with arbitrary IMF)

12. Modeling the Physics of Galaxy Formation SPH (GIMIC; Crain et al. 2010) SAM (Bower, Benson, Crain 2011) 10.0 11.0 12.0 9.0 SPH vs. SAM Stellar Mass Functions Overview | Models | Science | Collaboration • Two methods produce near identical results... • ...when assumptions are matched

13. Modeling the Physics of Galaxy Formation Decaying Dark Matter Overview | Models | Science | Collaboration X Y ζ • MY=MX(1-ε) • ε ≪ 1 • Y gets non-relativistic kick vk≈εc • Decay time is τ Peter & Benson (2010; PRD; 82, 3521)

14. Modeling the Physics of Galaxy Formation Decaying Dark Matter Overview | Models | Science | Collaboration

15. Modeling the Physics of Galaxy Formation • 25 m sub-mm telescope • Up to 1 square degree field of view • 200μm to 3mm wavelength range Caltech-Cornell Atacama Telescope CCAT Mock Surveys Overview | Models | Science | Collaboration Sky projection (degrees) Comoving coordinates (Mpc)

16. Modeling the Physics of Galaxy Formation Example SED Overview | Models | Science | Collaboration Stars Cirrus Molecular clouds Total

17. Modeling the Physics of Galaxy Formation GALACTICUSsites.google.com/site/galacticusmodel Summary Overview | Models | Science | Collaboration • Collaborate.... • Developing observing strategies • Getting predictions • Exploring the effects of different/new physics • Improving existing modeling of physics • ...or Don't Collaborate! • Model is freely available and well documented • Use it for what ever you want