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Simulating Proto-clusters utilizing the Austrian Grid

Michaela Lechner Eelco van Kampen Daniel Clarke Simon Ostermann Manchester, May 2007. Simulating Proto-clusters utilizing the Austrian Grid. Institute of Astro- and Particle Physics Distributed and Parallel Systems Group Institute for Computer Science.

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Simulating Proto-clusters utilizing the Austrian Grid

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  1. Michaela Lechner Eelco van Kampen Daniel Clarke Simon Ostermann Manchester, May 2007 Simulating Proto-clusters utilizing the Austrian Grid Institute of Astro- and Particle Physics Distributed and Parallel Systems Group Institute for Computer Science

  2. Protocluster Science is Sub-mm Science • Sub-mm needed for • High-z galaxy formation • High-z clusters (structure formation?) • Technology just starting to mature, breakthrough inevitable. • JCMT citation rate rivals HST! • At 850m, a galaxy has same flux density from z = 1 - 10 Sub-mm: 200μm - 1mm Millimeter:1mm - 10mm

  3. JCMT James Clerke Maxwell Telescope • Largest existing sub-millimeter one dish telescope in the world (diameter of 15m) • The JCMT is used to study our Solar System, interstellar dust and gas, and distant galaxies. • Situated close to the summit of Mauna Kea, Hawaii, at an altitude of 4092m (high & dry). • SCUBA: The Submillimetre Common-User Bolometer Array

  4. SHADES: SCUBA Half Degree Extragalactic Survey Lockman Hole East Subaru/XMM-Newton Deep Field It is not yet possible to measure the clustering properties of sub-mm sources. Redshift determination is currently in progress. (radio correlation)

  5. More sub-mm in the Future • ALMA: Atacama Large Millimeter Array • Herschel Space Observatory • SCUBA-2 (starting January 2008) ALMA HSO complete: 2012 operating: 2009 launched: 2007

  6. SCUBA-2 on JCMT • large 8 x 8 arcmin field-of-view • Simultaneous imaging at 450 and 850μm • Fully-sampled images of the sky in <4 seconds • bring “CCD-style” imaging to the JCMT for the first time • 20, 40 and 100 arc surveys are currently being planned using SCUBA-2 building on the understanding developed with SHADES and SCUBA1

  7. Simulating Observations Ingredients for a Semi-numerical Galaxy Formation: • Cosmological model (standard) • Halo formation and merger history • Gas dynamics and radiative cooling • Star formation and stellar feedback • Stellar population synthesis • Accurate Dust model CDM model of van Kampen, Rimes & Peacock (2004)

  8. Simulating Observations Ingredients for a Semi-numerical Galaxy Formation: • Cosmological model (standard) • Halo formation and merger history • Gas dynamics and radiative cooling • Star formation and stellar feedback • Stellar population synthesis • Accurate Dust model • only once • very fast • GRASIL • Initial data set currently created on HPC Cluster

  9. The Dust Model: GRASIL • Graphite and Silicone: principal contributors to galactic dust • Considers the physical effects of graphite, silicate and PAH particles on a galaxy’s SED • by Laura Silva (Gian Luigi Granato) 1999, FORTRAN 95 • Calculates the complex line integral between volume elements as a photon travels through the galaxy. Computationally intensive! Small code, small data files • Outputfiles: SED Data (1-2 kB) • Problem ideally suited for Grid Computing! Molecular cloud Bulge Disk Equatorial plane Diffuse ISM, Free stars and Cirrus Small code, small data files Outputfiles: SED Data (1-2 kB) All galaxies independent from each other

  10. Simulating Observations • Creation of Galaxy Formation model predictions: • Comparing predictions with future observations • Current lightcone with 60 timeslices à ~ 20.000 galaxies -> 1 million galaxies • Predicting whole lightcone -> usable for all telescopes and wavelength regimes • Protoclusters: • Only interested in part of the lightcone (relevant timeslices)

  11. Time Time Time Time Looking into the past P. Heinämäki, I. Suhhonenko, E. Saar, M. Einasto, J. Einasto, and H. Virtanen SPITZER Herschel SCUBA 2 ALMA

  12. Mock SCUBA-2 survey: ‘super-SHADES’ with 100 square degrees • including noise and observational effects • With a survey field of 100 square degrees, it seems statistically likely, based on dark matter simulations that both an over density region and blank field will be observed early in the survey. • . This is what we currently have

  13. SCUBA-2 legacy surveys 2 years 5 years

  14. Simulating Observations

  15. Porting to the Austrian Grid • Splitting one big parameter file into small parameter files for each galaxy • in generation of initial data set • in GRASIL • Compiling GRASIL in 3 different flavors: • generic 32 bit • AMD64 • Itanium 2 • Porting to the Austrian Grid reduces computational time per galaxy to approximately 4.2 seconds. (Lechner et al. 2007)

  16. ASKALON Workflow • Simple workflow: • Input Data Streamer Activity • Parallel Loop • Collector Activity • GRASIL Activity deployed on several Grid-sites, ‘embarrassingly parallel’.

  17. ASKALON Workflow • Preparation of data: Ruby script creating jobset-tarballs (future ASKALON will do it automatically) • less overhead • more balancing • (list of galaxies is not continuous) • Auto deployment of GRASIL • Performance monitoring/predictions

  18. Increasing code efficiency • Calculating the correlation matrix of the input parameters suggests that the following parameters are co-correlated with execution time: • Host machine • Radius of the Disk component • Cold gas mass • Cold gas metallicity • Total stellar mass • Bulge density Testrun with 25000 Galaxies on different Grid sites For each host type, there is a clear clustering of effective execution time.

  19. ASKALON • Local Installation or as a Java Webservice

  20. Autodeployment in ASKALON

  21. Blank Field

  22. Inserted proto-cluster @ z=2.5 • A proto-cluster at z≈2.5 significantly boosts the number of visible 850 μm sources, compared to a field-only map. Both maps are half a square degree in size with a resolution according to the JCMT beam.

  23. Matching sub-mm galaxy number counts Mock with no (proto)-cluster Mock with 1 (proto-)cluster Mock with 2 (proto-)clusters Underlying figure from Coppin et al. (2006)

  24. Finding proto-clusters in the SCUBA-2 and Herschel surveys Number overdensity of sub-mm sources for a field containing a rich proto-cluster increases with the flux cut.

  25. Conclusions I • Sub-mm observations is probably one of the most important wavebands in modern cosmology • With the next generation of Sub-mm surveys it seems likely that observations of over density regions will become common • Accurate simulations of proto-clusters will help us to understand the physics behind cluster and galaxy formation. • For simulations to ‘keep pace’ with detector technology developments, new computing techniques need to be adapted. • Urgency: Comparison with observations soon! • Extreme case of parallelization, huge amount of calculation power needed. • Input for Grid Middleware (ASKALON) improvement

  26. Conclusions II • Clustering is detected in SHADES, but with large uncertainties • Redshifts or large surveys are needed to improve upon this: the SCUBA-2 and/or Herschel legacy survey(s) • Bright sub-mm sources are mostly associated with high-density regions (proto-clusters and the like) • the contribution of (proto)-clusters to sub-mm source counts • ‘shallow’ (> 12 mJy) surveys are sufficient to find high-z (proto-)clusters

  27. Thank you!

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