Galaxy Formation, Theory and Modelling. Shaun Cole (ICC, Durham). Collaborators: Geraint Harker John Helly Adrian Jenkins Hannah Parkinson. ICC Photo: Malcolm Crowthers. 25 th October 2007. Outline. An Introduction to the Ingredients of Galaxy Formation Models
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ICC Photo: Malcolm Crowthers
Parkinson, Cole and Helly 2007
Insert an empirically motivated factor into this merger rate equation
Sheth-Tormen or Jenkins universal mass function is a good fit to N-body results at all redshifts.
Thus we require:
Very nearly consistent with the universal Sheth-Tormen/Jenkins Mass Function
NFW profiles, but with what concentration
Neto et al 2007
Helly et al. (2002)
Galaxy orbits decay due to dynamical friction
Cole et al 2000 fit to N-body results at all redshifts.Star formation and feedback processes
Benson & Bower 2003
Bower et al 2006
✶ fit to N-body results at all redshifts.
✶Stellar population synthesis and dust modelling
Star Formation Rate and Metallicity as a Function of Time + IMF assumption
Library of Stellar Spectra
Maraston 2005 fit to N-body results at all redshifts.Stellar population synthesis and dust modelling
Many Stellar Population Synthesis codes (eg Bruzual & Charlot, Pegase, Starburst99) are quite mature. But they aren’t necessarily complete.
Maraston (2005) showed that TP-AGB stars can make a dominant contribution in the NIR.
Star formation, feedback, SPS fit to N-body results at all redshifts.
Gas cooling rates
DM and Gas density profile
Galaxy merger rates
Dark Matter Merger Trees
Positions and velocities
Star formation rate, ages, metallicities
Structure & Dynamics
Semi-analytic fit to N-body results at all redshifts.+ N-body Techniques
Harker, Cole & Jenkins 2007
Particles in 300 Mpc/h box
Two grids of models with
Achieved by rescaling particle masses and velocities (Zheng et al 2002)
-- Grid 1
-- Grid 2
For each (scaled) N-body output we have two variants of each of three distinct GALFORM models.
Low baryon fraction (Cole et al 2000)
Superwinds (Baugh et al 2005 aka M)
AGN-like feedback (C2000hib)
Each model is adjusted to match the
observed r-band LF.
Select a magnitude limited sample with the same space density as the best measured SDSS sample.
Compare clustering and determine best fit.
Zehavi et al 2005
Comparison of models all having the same . density as the best measured SDSS sample.
Clustering strength primarily dependent on
I.E. Galaxy bias predicted by the GALFORM model is largely independent of model details.
The constraint on density as the best measured SDSS sample.
High values still density as the best measured SDSS sample.
The constraint on
from b-band 2dFGRS data
None of the models produce observed dependence of clustering strength on luminosity over the full range of the data.
More modelling work required.