Modeling the Physics of Galaxy Formation Andrew Benson California Institute of Technology

Scientific classification  Theorist Scale  Galactic – cosmological Wavelength range  Zero – infinity Favorite color  Dark matter

1 March 2011Modeling the Physics of Galaxy Formation3 Overview 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 Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation4 Advancing Galaxy Formation Codes 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. Overview | Models | Science | Collaboration G ALACTICUS sites.google.com/site/galacticusmodel

1 March 2011Modeling the Physics of Galaxy Formation5 Design Features 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) Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation6 Design Features Well documented Promotes a standard format for merger tree data  Parallelized  OpenMP  MPI (soon...)  Currently simple, but allows for expansion Source code Binaries Cloud (Amazon EC2) Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation7 External Tools GNU Scientific Library/ FGSL  ODE solver; integration; other numerics FoX library  Read/write XML files FSPS  Population synthesis Cloudy  Cooling times Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation8 Modularity 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 Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation9 Current Feature List 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. Tracks mass and spin. Spin from mergers and accretion. Accretion spin-up using Benson & Babul formula Jet power from Benson & Babul also. Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation10 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) Current Feature List Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation11 Current Feature List Physics (cont.):  Disk instabilities  Black hole merging  AGN feedback  Stellar population synthesis (with arbitrary IMF) Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation12 SPH vs. SAM Stellar Mass Functions SPH (GIMIC; Crain et al. 2010) SAM (Bower, Benson, Crain 2011) Two methods produce near identical results... ...when assumptions are matched Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation13 Decaying Dark Matter Overview | Models | Science | Collaboration Peter & Benson (2010; PRD; 82, 3521) X Y ζ M Y =M X (1-ε) ε  ≪ 1 Y gets non-relativistic kick v k ≈εc Decay time is τ

1 March 2011Modeling the Physics of Galaxy Formation14 Decaying Dark Matter Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation15 CCAT Mock Surveys Comoving coordinates (Mpc) Sky projection (degrees) Overview | Models | Science | Collaboration 25 m sub-mm telescope Up to 1 square degree field of view 200μm to 3mm wavelength range Caltech-Cornell Atacama Telescope

1 March 2011Modeling the Physics of Galaxy Formation16 Example SED Stars Cirrus Molecular clouds Total Overview | Models | Science | Collaboration

1 March 2011Modeling the Physics of Galaxy Formation17 Summary 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 Overview | Models | Science | Collaboration G ALACTICUS sites.google.com/site/galacticusmodel