Landau Damping of Baryonic Structure Formation in the

Landau Damping of Baryonic Structure Formation in the Post Reionization Epoch Arxiv: 1006. 5777 Feng-Yin Chang Leung Center for Cosmology and Particle Astrophysics (Le. Cos. PA) , National Taiwan University COSMO/Cos. PA 2010 , Tokyo 1

Reionization plasma neutral gas plasma from QSO spectrum ( from WMAP 7) Bolton, et al (2010) Becker, et al (2001) Larson, et al (2010) 2

Previous Studies • Effects of reionization on intergalactic medium (IGM) and low-mass galaxies were studied by many researches. • In 1986, Rees and Ikeuchi independently pointed out the increasing of gas temperature during reionization could suppress the formation of small galaxies with mass less then Jeans mass. Ikeuchi AP&SS(2986) Rees, as MNRAS scale the (1986) • Gnedin (2000) proposed the filtering characteristic scale for the baryonic fluctuation, instead of Jeans scale, for linear and nonlinear regimes. Gnedin, Ap. J (2000) • Chen and Lai (2007) first consider the plasma collective effects on the baryonic structure formation, but their calculation is incomplete. P, Chen& KC La, i PRL(2007) 3

Why Plasma Effects? Three Plasma Criteria: Plasma collective effects: plasma wave, Landau damping, instabilities…. 4

Plasma Waves 5

Linear Fluid Equations ionized gases plasma For mean molecular weight 6

Landau Damping The nonlinear empirical formula F. Chen 0. 4 of one oscillation period the ion acoustic wave would be Landau-damped to e-fold of its initial amplitude. 7

Solution of Baryon Fluctuation For simplicity, const. damping where oscillation part 8

Results For Ionized gas Gnedin &Hui, MNRAS(1998) ionized gas plasma w LD The suppression of modes with intermediate and high k due to Landau damping gives rise to a correction of kf plasma w/o LD F. Y. Chang, P. Chen, Ar. Xiv: , 1006. 5777 9

Modified Filtering Scale F. Y. Chang, P. Chen, Ar. Xiv: , 1006. 5777 10

Results ionized gas plasma The two characteristic wavenumbers for plasma and ionized gas deviate larger in high redshift. 11

Landau Damping on Early Evolution ionized gas plasma The small-scale baryon acoustic oscillations in early post-reionization epoch can help distinguish the models 12

Recent measurements We seek for a cosmological survey for small-scale structure formation. Tegmark et. al, 2002 We are here 13

Summary • The plasma collective effects on baryonic structure formation in the post-reionization is considered. • Two major plasma influences: sound speed and Landau damping. • The ion acoustic modes were rapidly smoothed out due to the Landau damping. • The Landau damped spectrum should be characterized by a modified filtering scale. • Measurement of small-scale baryonic oscillation is essential to learn the nature of the cosmic structure formation. 14