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  • A workshop dedicated to the Theoretical Virtual Observatory will take place at IAP on April 5-6th.

    The goal is to bring together experts of the Virtual Observatory and theoreticians who would like to make results of their simulations (e.g. databases or catalogs) or numerical codes available to the worldwild astronomical community.

  • Program and speakers

Horizon NYC Workshop

"Extreme" Cosmological Hydro Simulations

by Devriendt Julien (Tuesday 11 April 2006)

- Information
- Program
- Participants
- Conclusion

Practical Information:

The workshop will take place from the 19th to the 22nd of December 2005 in New York City and will be hosted by Greg Bryan ( at the Department of Astronomy of Columbia University.

Participants will be lodged at the Milburn Hotel:

The Milburn Hotel
242 West 76th Street
New York, NY 10023
Tel: (212)-362-1006
Toll Free: 1-800-833-9622

Participants are expected to pay for their hotel rooms themselves (at the Columbia rate of $145/night+tax), and to later get reimbursed by sending their receipts to Romain Teyssier at the following address:

Service d’Astrophysique
CEA Saclay Batiment 709
L’Orme des Merisiers
F-91191 Gif-sur-Yvette Cedex
Fax: +33 1 69 08 65 77

The meeting will take place in room 1402 (14th floor Library) of the Pupin Physics Lab, which is located in the north-west corner of the Columbia campus. The main campus entrance is at 116th St. and Broadway. Directions to the Pupin Physics Lab can be found at:

The easiest way to get from the hotel to the Columbia campus is to take the number 1 (red) subway in the Uptown direction to the 116th street stop (5 stops). The subway costs $2 per ride and requires the purchase of MetroCards, which can be bought using automatic machines in any subway station. The subway stop nearest to the Milburn hotel is at the corner of 79th St. and Broadway. For a subway map, see

The hotel is just a few blocks away from The American Museum of Natural History (79th St and Central Park West), and of course, just a few blocks from Central Park itself.


The main goal for this meeting is to come up with a list of the best possible "extreme" simulations related to galaxy formation in a cosmological context, where best is to be understood in terms of the science they will address. By "extreme" we mean either extremely large simulations (e.g. 10 billion particles and hydro cells, 5 levels of AMR refinement) or extremely resolved simulations (e.g. 10 million particles and hydro cells but 30 levels of AMR refinement), or a combination of both :-). Therefore, we will have to review / discuss the supercomputers available to run such simulations, and the codes most suited to run them.

As this is a workshop, the major part of the time is obviously devoted to discussion. However, to trigger and lead these discussions we have chosen a format in which a general presentation of a hot scientific topic — which is expected to last about 15 minutes and certainly no more than a half hour — is given by a "chair(wo)man" or "pundit" which naturally opens on a question / discussion session. In summary, a short presentation, a list of key questions to address / discuss and an example of an "extreme" simulation designed to tackle a key issue is requested from each of the primary presenters / discussion leaders.

Of course, all participants are more than invited (especially those who do not chair a session) to prepare questions / issues they would like to see discussed for each topic.

As a tentative title for the workshop, one could then think of:

"Extreme" Cosmo Hydro Simulations: Which Scientific Issues To Address?

A list of possible topics with a loose schedule and suggested chair would then be:

Monday morning (9:30 am - 12 pm):

  • Numerical techniques and supercomputing centers: state-of-the-art and availability vs size of simulations.
PDF - 1.1 Mb
R. Teyssier’s presentation

Chairman: Romain Teyssier

Monday afternoon (1:30 pm - 4 pm):

  • First stars, proto-galaxies and reionization.
PDF - 5.2 Mb
G. Bryan’s presentation

Chairman: Greg Bryan

Tuesday morning (9:30 am - 12 pm):

  • ISM: molecular cloud and star formation within galaxies
PowerPoint - 19.6 Mb
A. Slyz’s presentation

Chairwoman: Adrianne Slyz

Tuesday afternoon (1:30 pm - 4 pm):

  • High-z (but post-reionization) galaxies (LBG-like objects) and their impact on the IGM
PowerPoint - 6 Mb
A. Kravtsov’s presentation

Chairman: Andrey Kravtsov

Wednesday morning (9:30 am - 12 pm):

  • Galaxies in Clusters and Groups (at high and low z): interactions with and impact on the ICM
PowerPoint - 14 Mb
G. Yepes’ s presentation

Chairman: Gustavo Yepes

Wednesday afternoon (1:30 pm - 4 pm):

  • Galaxies in Large Scale Structures
PDF - 14.3 Mb
J. Blaizot’s presentation

Chairman: Jeremy Blaizot

Thursday morning (9:30 am - 12 pm):

  • Summary of the Workshop: consensus ranking of what are the "most sexy" extreme simulations

Chairman: Stefan Gottloeber

List of participants:

Surname First Name Arrival Date Departure Date
Aubert Dominique 18/12/2005 22/12/2005
Blaizot Jeremy 18/12/2005 22/12/2005
Bryan Greg 18/12/2005 22/12/2005
Devriendt Julien 18/12/2005 22/12/2005
Gottloeber Stefan 17/12/2005 22/12/2005
Kravtsov Andrei 18/12/2005 22/12/2005
Pichon Christophe 18/12/2005 22/12/2005
Rasera Yann 18/12/2005 22/12/2005
Slyz Adrianne 18/12/2005 22/12/2005
Sousbie Thierry 18/12/2005 22/12/2005
Teyssier Romain 18/12/2005 22/12/2005
Yepes Gustavo 17/12/2005 21/12/2005

Brief summary / conclusions of this workshop:

The workshop led to the conclusion that to cover all aspects of galaxy formation (overlap of length and mass scales from proto-galaxies at high redshift to cD monster galaxies located at the center of the richest clusters), one would need a set of minimum 3 extreme simulations:

  • A large box (500 Mpc/h) to obtain a statistically meaningful sample of massive (10 keV) clusters, extremely massive (and rare) galaxies up to moderate redshift (z 1-2) and study their spatial distribution
  • A medium box (100 Mpc/h) to cover intermediate redshifts and the mass assembly of Lyman Break Galaxies at z 3-4, linking them to their local descendents
  • A small box (20 Mpc/h) to tackle high redshift proto-galaxies (z 20) and their impact on the reionization of the Universe

As discussed, the baryon physics to be implemented in each of these runs will be different: simple adiabatic hydrodynamics for the large box; atomic cooling, UV background flux and standard star formation and feedback recipes for the medium box; molecular cooling and post-processing radiative transfer for the small box.