arXiv:0806.4119v1 [astro-ph] 25 Jun 2008 Mem. S.A.It. Vol. 75, 282 c  SAIt 2008 Memorie della R. Salvaterra 1 , C. Burigana 2,3 , R. Schneider 4 , T. R. Choudhury 5 , A. Ferrara 6 , and L. A. Popa 7,2 1 INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (LC), Italy. e-mail: salvaterra@mib.infn.it 2 INAF-IASF Bologna, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, Istituto Nazionale di Astrofisica, via Gobetti 101, I-40129 Bologna, Italy 3 Dipartimento di Fisica, Universit` a degli Studi di Ferrara, via Saragat 1, I-44100 Ferrara, Italy 4 INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy 5 Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK 6 SISSA/International School for Advanced Studies, Via Beirut 4, I-34100 Trieste, Italy 7 Institute for Space Sciences, Bucharest-Magurele, Str. Atomostilor, 409, PoBox Mg-23, Ro-077125, Romania Abstract. We explore the effect of cosmic radiative feedback from the sources of reioniza- tion on the thermal evolution of the intergalactic medium. We find that different prescrip- tions for this feedback predict quite different thermal and reionization histories. In spite of this, current data can not discriminate among different reionization scenarios. We find that future observations both from 21-cm and CMB experiments can be used to break the de- generacy among model parameters provided that we will be able to remove the foreground signal at the percent (or better) level. 1. Introduction It is well known that the temperature increase of the cosmic gas in ionized regions leads to a dramatic suppression of the formation of low-mass galaxies (see Ciardi & Ferrara 2005 for a review). We explore the impact of this effect during cosmic reionization by considering two different feedback prescrip- tions: (i) suppression model where galax- ies can form stars unimpeded provided that their circular velocity is larger than a criti- cal threshold, which is not fixed to a constant value but evolves according to gas tempera- ture (Choudhury & Ferrara 2006); (ii) filtering Send offprint requests to: R. Salvaterra model, where, depending on the mass of the galaxy, the fraction of gas available to star for- mation is reduced with respect of the universal value and it is fully specified by the filtering mass at that redshift (Gnedin 2000). We implement these two different radia- tive feedback prescriptions into a physically- motivated and observationally tested model of reionization (Choudhury & Ferrara 2005; Choudhury & Ferrara 2006). Although the two feedback prescriptions predicts quite different reionization and thermal histories (see Fig. 1), in both scenarios it is possible to reproduce a wide range of observational data with a proper choice of few model parameters (the redshift evolution of Lyman-limit absorption