Following Haloes going MAD, Subhaloes going Notts, Sussing Merger Trees, and Halo Mass Recovery we will now run a

three week workshop examining the production and analysis of mock universes

which are nowadays routinely used to underpin the science return from large observational surveys such as DES, Euclid & BOSS. We intend to run three tightly coupled ateliers back-to-back in June/July 2014 addressing:

i)The modeling of individual galaxy clusters and their impact on cluster cosmology.

ii)The production of mock galaxy catalogues, using both semi-analytical models and approximative methods

iii)The extraction of observational results from the artificial skies generated during the first two weeks.

This workshop will address the credibility of the simulations and derived mock surveys that are commonly used for large scale structure determination by verifying the various techniques before validating them against observational data.

Week #1 - nIFTy clusters:

The very first comparison project ever undertaken in (computational) cosmology was initiated by Carlos Frenk in Santa Barbara in the year 1994. It led to a seminal paper published in 1999 (Frenk et al. 1999) where several codes for performing (non-cooling) hydrodynamical simulations were compared against each other with a special focus on the radial profile of a galaxy cluster. It was found that grid and particle based codes differ substantially, an issue still not solved today. We feel that it is time to repeat the same comparison with a suite of modern codes. Once the non-cooling comparison has been completed simulations studying the effects of cooling and additional physics such as AGN and supernovae feedback are straightforward to add.

Data: selection of MUSIC-2 clusters.

Week #2 - nIFTy galaxies:

Our previous workshops examined the extraction and linking of the gravitationally bound structures that form within cosmological simulations.The natural continuation of this work is to add mock galaxies using a variety of modern techniques of varying complexity ranging from approximative methods to full semi-anaytic models. While there have been previous attempts at comparing different techniques for converting dark matter only simulations into luminous galaxy catalogues, none of them featured the unique advantage of a well defined, portable standard merger tree format which several of the current semi-analytic models can already use as input. At a slightly lower level of complexity, observational quantities are guaranteed to be recovered if the galaxies are added more "by hand", for instance via halo occupation density (HOD) or subhalo abundance matching (SHAM) techniques.  Further, the desire to estimate the errors in the cosmological parameter determination in recent years has seen the advent of methods that try to bypass the actual simulation (PThalos from Mark Manera, QPM from Martin White, DPhalos by Santiago Avila-Perez, PATCHY by Francisco Kitaura, COLA by Svetlin Tassev, etc.), but so far no one has even tried to compare the results and hence gauging their credibility against each other.

Data: standardized merger trees (cf. Srisawat et al. 2013) built from the CURIE universe simulation.

Week #3 - nIFTy observations:

Simply generating mock galaxies and clusters is not the end of the story. These synthetic Universes need to be observed. This process involves the generation of a lightcone that mimics the observational process that can then be analysed using a procedure that closely follows that undertaken using real data. We have already held one workshop looking at this process to act as a pathfinder for this proposed event. A lightcone will be selected in advance that passes through the resimulated region studied by the nIFTy clusters project as well as cutting through the galaxy catalogues made by the nIFTy galaxies. We will then examine how well observational quantities such as cosmological parameters as well as galaxy cluster location and size are extracted using current observational techniques.

Data: lightcone, built using the CURIE universe simulation and associated mock galaxy catalogues and hydrodynamical information from nIFTy clusters and nIFTy galaxies.

There are 4 distinct workgroups you can (and should) sign up for by sending an email to the coordinator:

1. ★week #1: cluster comparison project (coordinated by G. Yepes)
   

2. ★week #2: semi-analytical model comparison (coordinated by A. Knebe & F. Pearce)
   

3. ★week #2: approximative methods for mock galaxy catalogues comparison (coordinated by F. Prada)
   

4. ★week #3: lightcone observations (coordinated by F. Pearce & C. Power)
   

to register for the workshop, please send an email to

nIFTyCosmology2014@gmx.de