Search

ABSTRACT WMAP's detection of high electron-scattering optical depth τ[sub e] suggests substantial star formation at high redshift z∼ 17 ± 5 . On the other hand, the recovered σ[sub 8]∼ 0.84 ± 0.04 argues against a cluster Sunyaev–Zeldovich (SZ) origin for the observed small-scale cosmic microwave background (CMB) fluctuation excess, which generally requires σ[sub 8]∼ 1.1 . Here we consider the effects of high-redshift star formation on the CMB. We derive a fairly model-independent relation between τ[sub e] and the number of ionizing photons emitted per baryon N[sub γ] , and use this to calibrate the amount of high-redshift supernova activity. The resulting supernova remnants Compton cool against the CMB creating a Compton y distortion y∼ few × 10[sup -6] within observational bounds. However they also create small-scale SZ fluctuations, which could be comparable with SZ fluctuations from unresolved galaxy clusters. This raises the exciting possibility that we have already detected signatures of the first stars not just once, but twice, in the CMB. [ABSTRACT FROM AUTHOR]

Abstract We show that gas in a large fraction of low-mass dark matter haloes may form Toomre-stable discs, if angular momentum is conserved when the gas contracts. Such haloes would be stable to star formation and therefore remain dark. This may potentially explain deviation between the predicted and the observed faint-end slope of the luminosity function and the discrepancy between the predicted and observed number of dwarf satellites in the Local Group. The above mechanism does not require a strong variation of the baryon fraction with the virial mass of the dark halo. We show that model fits to rotation curves are also consistent with this hypothesis: none of the observed galaxies lies in the region of parameter space forbidden by the Toomre stability criterion. [ABSTRACT FROM AUTHOR]