Colloquium 111: Dark matter and stellar mass assembly since z=7 (Prof. Sebastien R.A. Foucaud, Apr.03, 2013)

Title: Dark matter and stellar mass assembly since z=7

Speaker: Prof. Sebastien R.A. Foucaud,Department of Earth Sciences, National Taiwan Normal University

Location: Room 111, Physics Building

Time: 15:00-16:00p, April 3rd, 2013

Abstract:

The past and coming few years see the advent of new generations of deep and wide surveys in optical and near-infrared, which enable us to explore the evolution of galaxies on range of redshifts and masses never explored so far. Owing to my involvement to some of the most important of these surveys, I am exploring the mass assembly history of galaxies since z=7. As the large-scale behavior of galaxies is ruled by their dark matter content, an estimate of the mass of their dark matter halos is crucial to gain a good understanding of the history of their mass assembly. Clustering analyses allows us to link galaxy populations to the mass of their host haloes, and I am using this technique to probe the halo masses of galaxies up to z=7. In particular, I am interested in the luminous-to-dark mass ratio and its evolution with redshift. These results implied that a halo downsizing is in place since z=2, where galaxy mass assembly happen faster in higher mass haloes at high redshifts while at lower redshifts it migrates to lower mass halos.

I also demonstrate that the (stellar) baryonic mass of galaxies are not as well correlated to the mass of their dark matter haloes as expected, and even by involving gaseous mass, the budget of mass is not compatible with the baryonic fraction implied by cosmological studies (CMB).

To understand better the origin of these missing baryons, I am exploring directly the mass assembly of galaxies by major mergers. I demonstrate that since z=2 while major merger plays a minor role in mass assembly of the most galaxies, it plays an increasingly important role in the lower mass galaxies, in particular at low redshift, in contradiction with the theoretical predictions.

Finally I will conclude on the challenges raised by the exploitation of the current and next generation of large surveys, and how they required development of topics such as Astroinformatics and Virtual Observatory.

Biography:

Research Interests：

• Formation and Evolution of Galaxies
• Large Scale Structure
• Clusters and groups of Galaxies
• Multiwavelength surveys and Virtual Observatories

Professional experience：

• 2009- : Assistant Professor, Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan
• 2005-2009: Research fellow, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom
• 2003-2005: Postdoctoral Fellow, Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan, Italy

Education：

• 1999-2003: PhD in Astrophysics, Université de Provence, Marseille, France
• 1998-1999: Msc in Astrophysics and Astronomy, Université Claude Bernard, Lyon, France
• 1996-1998: Bsc in Physics, Université Paul Sabatier, Toulouse, France