Thursday, October 20 14:00 - 16:00 (ENS - Big CECAM)

Dear all, on the occasion of the TODAI Forum we have two collaborators visiting. Unfortunately, the date coincides with the MUSE workshop at the observatory. The TODAI Forum is continued in Paris and accompanied by a conference on the Acceleration of the Universe : http://www.iap.fr/coldenet/ We decided to do a mini-workshop at ENS comprising two talks. Everybody is welcome !

Programme

Exoplanets

 14:00 Yasushi Suto (Todai, Tokyo) : Colors of a second Earth : towards exoplanetary remote-sensing

Abstract : We develop a simple method to estimate the fractional areas of different surface types on earth-like exoplanets from multi-band photometry. Our attempt is to reproduce the scattered light curves as a sum of the 5 surface types, i.e., ocean, soil, vegetation, snow and cloud. We would like to answer an ambitious, but well-defined, scientific question : "If we discover an exoplanet identical to the Earth in the near future, can we infer the presence of vegetation observationally ?’’. This is why we intentionally and specifically adopt the major surface types of the Earth, including vegetation, into the analysis even though our method is thus inevitably model-dependent. We apply our method to mock scattered light curves of the Earth and to the real data from the Earth observing satellite. In an idealized situation where the photometric errors are only photon shot noise, we are able to reproduce the fractional areas of those components fairly well. We may be even able to detect a signature of vegetation from the distinct feature of photosynthesis on the Earth, known as the red edge. In our reconstruction method, Rayleigh scattering due to the atmosphere has an important effect, and for terrestrial exoplanets with atmosphere similar to our Earth, it is possible to estimate the presence of oceans and an atmosphere simultaneously.

References :

1. Yuka Fujii, Hajime Kawahara, Yasushi Suto, Atsushi Taruya, Satoru Fukuda, Teruyuki Nakajima, and Edwin L. Turner : “Colors of a second Earth I : estimating the fractional areas of ocean, land and vegetation of Earth-like exoplanets” The Astrophysical Journal 715, 866—880, 2010.
2. Yuka Fujii, Hajime Kawahara, Yasushi Suto, Satoru Fukuda, Teruyuki Nakajima, Timothy A. Livengood, and Edwin L. Turner : “Colors of a second Earth II : Effects of clouds on photometric characterization of Earth-like exoplanets” The Astrophysical Journal 738, 184(1-15), 2011.

Large Scale Structure

 15:00 Chiaki Hikage (Univ. of Princeton) : Synergy analysis with galaxy imaging and redshift surveys

Abstract : Wide-field galaxy imaging and redshift survey aims for uncovering the accelerated expansion in the universe. The largest source of systematic uncertainty in this analysis is the challenge of modeling the complex relationship between galaxy redshift and the distribution of dark matter. I will talk about how the synergy analysis reduces the systematic uncertainties due to galaxy biasing and Finger-of-God effect.

Reference : C. Hikage, M. Takada, D. Spergel : "Using galaxy-galaxy weak lensing measurements to correct the Finger-of-God" http://arxiv.org/abs/1106.1640

See the list of forthcoming seminars here