Welcome to my scientific web page

General presentation

My name is Jean-Julien Fleck (a bit difficult to pronounce for non french people… just call me JJ). I was a PhD student in astrophysics at the Strasbourg Observatory working on numerical simulation of star clusters within interaction galaxies under the supervision of C. Boily. I have been defending my thesis with success on tuesday 31st of july 2007. You can have a look to the manuscript (in french). I’m now teaching physics in a MPSI ``classe préparatoire’’ in Nancy ``Lycée Henri Poincaré’’.

If interested, you can look at my complete CV (in french) or at my former website at the École Normale Supérieure where I studied theoretical physics (with a bit of practice from time to time) from 2000 to 2004

Scientific interest

My interest in astrophysics are multiple and mostly theoretical:

• Using a gaseous model program named GasTel, I have been studying the influence of mass segregation on estimating the mass of young unresolved star clusters.

• I have also reconducted the previous simulations with a direct nbody integrator, namely nbody6, or its parallelized counterpart nbody6++. My parallel runs have mainly been conducted at the High Computing Centers of Illkirch-Graffenstadten in Alsace and of Edinburgh within the framework of the program HPC-Europa.

• On a larger scale, I have been studying the direct merging of two galaxies chosen to mimic the NGC 4038-39 system, also known under the name of the “Antennae”. To do this, I used the NEMO stellardynamical toolsbox and especially the fast integrator gyrfalcON.

• As I am mainly interested in monitoring the evolution of young star clusters that could be formed during such violent tidal interactions, it would be interesting to include tidal effects directly in nbody6[++], I thus wrote an extension to nbody6[++] that can apply any external tidal field when giving the program the evolution in time of the tidal tensor retrieved from gyrfalcON simulations.

• I spent some time at the Institute for Astronomy in Hawaii working on the time varying tidal effect of the Milky Way on dwarf spheroidal galaxies incollaboration with Jeff Kuhn. I still plan to study resonance effect on these systems with gyrfalcON.

Programming skills and projects

• nbody6 and GasTel being written in FORTRAN, I had to learn this language in order to make my programs compute interesting quantities.

• Nevertheless, my predilection programming language remained Perl, whose flexibility made it easy to analyse FORTRAN outputs. If some applications required fast computing abilities, I found it easier to write a perl program that writes, compiles and run a FORTRAN program on the fly (I wrote once the same heavy computing program in perl and Perl/FORTRAN and the latter ran 30 times faster…). Some such scripts that could be of interest are available below.

• I discovered quite recently (2006) Ruby and felt quite in love with its object-oriented programming paradigm. Thus all my late programming has been made with Ruby. Vincent Fourmond has convinced me to help him programming and documenting its SciYAG project and in particular ctioga which is a command-line plotting tool based on Tioga by Bill Paxton (one of the designer of PostScript, not the movie actor).

List of Publications

• Parametric Dwarf Spheroidal Tidal Interaction with Jeff Kuhn, 2003
• On the Mass of Dense Star Clusters in Starburst Galaxies from Spectro-Photometry, with C. Boily, A. Lançon and S. Deiters, 2006

Talks, posters and attended meetings

• First Hoher List Meeting, 15 October 2004, talk: pdf
• Edinburgh’s MODEST 5a Meeting, 15 December 2004, talk: pdf, interactive movie
• Vienna, 16 February 2005, talk, pdf, interactive movie
• SF2A, Strasbourg, 27 June 2005, talk: pdf, interactive movie
• Amsterdam MODEST Summer School, july 2005, talk: movie together with Nicolas Kielbasiewicz
• Second Hoher List Meeting, november 2005, talk: pdf, interactive movie
• Lund’s MODEST 6a Meeting, december 2005
• Vienna visit, february 2006, talk: pdf, interactive movie
• CAW, talk: pdf, interactive movie
• Lunteren, june 2006, poster: pdf
• PhD defence, july 2007: interactive movie

Some (useful?) scripts

Here are some scripts I wrote and that I am using daily. Most of them are related to my work but some could be of general interest.

Perl scripts

• mkpgp automaticaly builds up the skeleton of a new Perl script
• mkpgpf automaticaly builds up the skeleton of a new FORTRAN program embedded within a Perl script to more easily handle options
• PrendreLigneEvery mini-script to select one line of a file every some others. Useful to reduce data sets.
• OrbitePotentielFige integrates the orbit of several particles given in a x y z vx vy vz format (number of particles on first lign) in the fixed potential created by several source particles given in a m x y z format (number of particles on first lign) using a Leap-Frog integrator

Ruby scripts

• mkpgr automaticaly builds up the skeleton of a new Ruby script to easily manage option stuff. You need the Program library to use it.
• vtioga is browser-based viewer that uses Tioga to create the pdfs, converts them to png’s, and then displays them in a browser page created using Ruby on Rails. The browser page has thumbnails for all the figures in the file —click them to see a larger version. The version is still in an alpha prerelease state so tell me if you encounter any problem. The installation is described in the tutorial
• mkthese is a Ruby script for PhD students finishing their thesis. At the time of redaction, you will find that the thesis overall structure can change a lot depending on the last state of your researchs. To be able to compile atomicaly each part of my own thesis, I wrote this convenient script which compile automaticaly all the needed TeX files. It does not (yet) write the thesis in itself but is certainly not far from it.