Research interests

Summary

My research cover both the observations and the modeling of the matter dynamics, essentially the dark section, from intermediate scales, of a few Megaparsecs, to the largest scales accessible through CMB, several Gigaparsecs. I am using the consequences of this dynamics to derive methods for determining constraints on the physics of the Universe, e.g. the Dark Energy. I am applying these methods to observations.

I am interested in observations of large sets of galaxies, modeling the formation of Large Scale structures, and studying their impacts on other observables like the Cosmic Microwave Background.

Work on the kinetic Sunyaev-Zel’dovich effect

During a four month internship in Oxford in 2003, I used a number of simulations to check the importance of the second order Sunyaev-Zel’dovich effect of the cluster of galaxies on the CMB polarization (astro-ph/0307293). During this internship I also tried to setup a major cluster merger to study a transient state of the gas dynamics in the center of clusters called “cold front” (astro-ph/0312015). To achieve those two projects, I had to build new tools capable of simulating how photons properties are modified by the scattering on the particles of the inter-galactic medium (IGM). A report of my activities during my internship are available here.

Peculiar velocities of galaxies

Between September 2005 and September 2008, I did my Ph.D. on the reconstruction of peculiar velocities of galaxies or groups of galaxies from available redshift survey. To achieve that we used a recently developed technique, called the Monge-Ampère-Kantorovitch reconstruction, which, under fair hypotheses, is capable to predict the current velocity of a cosmological object (galaxy, cluster of galaxies) from its current position. The method has been successfully checked against simulations (astro-ph/0501217). The first aim was to prove it may really work using a distribution of galaxy given in redshift coordinates, thus in the presence of finger-of-gods and redshift distortion. I ended up with a thorough study on observational biases in cosmic velocity field reconstructions (0707.3483). I had to understand exactly how a bad knowledge on the position, the mass and on catalog boundaries would affect the reconstructed peculiar velocities.

I am continuing the work on peculiar velocities by attempting a Bayesian model of the velocity field.

Catalogs of galaxies

I am currently trying to do measurements based on real redshift data such as the 2MASS redshift survey used in conjunction with galaxy distance measurements by Brent Tully. I hope to apply also the method to SDSS data, which instead of having a full sky coverage provide a really interesting deep survey as far as MAK reconstruction is concerned.

With my collaborator, Michael J. Hudson, we have built a deep extension of the 2MASS Redshift Survey, which we dubbed the 2M++ galaxy redshift catalog. This catalog is going to be soon publicly available (expected May 2011).

Perturbative expansion of dynamics

My other interests in cosmology cover extension to higher orders of Zel’dovich approximation, N-body simulations and statistics on large scale structures (2 point correlation function and probability density of cell occupancy by a galaxy).

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