Motivated by recent evidence that the epoch of reionization of hydrogen may have ended at a redshift as low as z ≈ 6, we consider the detectability of the sources responsible for this reionization. The main idea is that reionization places limits on the mean surface brightness of the population of reionization sources. Reducing the number of model-dependent assumptions to a minimum, we discuss ...

Ionized gas and stellar kinematical parameters have been measured along the major axis of 20 nearby disc galaxies. We discuss the properties of each sample galaxy distinguishing between those characterized by regular or peculiar kinematics. In early-type disc galaxies ionized gas tends to rotate faster than stars and to have a lower velocity dispersion (Vg > V⋆ and σg < σ⋆), whereas in late-typ...

We prove that almost every real quadratic map is either regular or Collet-Eckmann. This implies exponential rates of mixing of the last renormalization of the map. We also show that the recurrence of the critical orbit is polynomial in a full measure set. It follows from a result of Baladi and Viana that almost every quadratic map is stochastically stable in the strong sense. Combined with meth...