%0 Generic %1 bouwens2015cosmic %A Bouwens, R. J. %A Illingworth, G. D. %A Oesch, P. A. %A Caruana, J. %A Holwerda, B. %A Smit, R. %A Wilkins, S. %D 2015 %K galaxy high-z reionisation %T Cosmic Reionization after Planck: The Derived Growth of the Ionizing Background now matches the Growth of the Galaxy UV Luminosity Density %U http://arxiv.org/abs/1503.08228 %X Thomson optical depth measurements from Planck provide new insights into the reionization of the universe. To obtain new model-independent constraints on the properties of the ionizing sources, we determine the empirical evolution of the ionising background. We use a simple two-parameter model to map out the evolution in this background at z>~6 from the new Planck optical depth tau measurements and from the constraints provided by quasar absorption spectra and the prevalence of Ly-alpha emission in z~7-8 galaxies. We find the redshift evolution in the ionising background N_ion required by the observations to be dlog_10 N_ion/dz(z=8)=-0.19_-0.11^+0.09, largely independent of the assumed clumping factor C_HII and entirely independent of the identity of the ionizing sources. The trend in N_ion is well-matched by the evolution of the galaxy UV-luminosity density (dlog_10 rho_UV/dz=-0.11+/-0.04) to a magnitude limit >~-13 mag, suggesting that galaxies are the sources that drive the reionization of the universe. The role of galaxies is further strengthened by the conversion from the UV luminosity density to N_ion(z) being possible for physically plausible values of the escape fraction f_esc, the Lyman-continuum photon production efficiency xi_ion, and faint-end cut-off M_lim to the LF. Lastly, we use the inferred evolution in the ionizing background to estimate the z~10 UV luminosity density, finding this luminosity density to be 12_-7^+21x lower than at z~6, consistent with current measurements at z~10. Quasars/AGN appear to match neither the redshift evolution nor normalization of the ionizing background. This new approach of contrasting the inferred evolution of the ionising background with that of the galaxy UV luminosity density adds to the growing observational evidence that galaxies are the sources that drive the reionization of the universe.

@misc{bouwens2015cosmic, abstract = {Thomson optical depth measurements from Planck provide new insights into the reionization of the universe. To obtain new model-independent constraints on the properties of the ionizing sources, we determine the empirical evolution of the ionising background. We use a simple two-parameter model to map out the evolution in this background at z>~6 from the new Planck optical depth tau measurements and from the constraints provided by quasar absorption spectra and the prevalence of Ly-alpha emission in z~7-8 galaxies. We find the redshift evolution in the ionising background N_{ion} required by the observations to be dlog_{10} N_{ion}/dz(z=8)=-0.19_{-0.11}^{+0.09}, largely independent of the assumed clumping factor C_{HII} and entirely independent of the identity of the ionizing sources. The trend in N_{ion} is well-matched by the evolution of the galaxy UV-luminosity density (dlog_{10} rho_{UV}/dz=-0.11+/-0.04) to a magnitude limit >~-13 mag, suggesting that galaxies are the sources that drive the reionization of the universe. The role of galaxies is further strengthened by the conversion from the UV luminosity density to N_{ion}(z) being possible for physically plausible values of the escape fraction f_{esc}, the Lyman-continuum photon production efficiency xi_{ion}, and faint-end cut-off M_{lim} to the LF. Lastly, we use the inferred evolution in the ionizing background to estimate the z~10 UV luminosity density, finding this luminosity density to be 12_{-7}^{+21}x lower than at z~6, consistent with current measurements at z~10. Quasars/AGN appear to match neither the redshift evolution nor normalization of the ionizing background. This new approach of contrasting the inferred evolution of the ionising background with that of the galaxy UV luminosity density adds to the growing observational evidence that galaxies are the sources that drive the reionization of the universe.}, added-at = {2015-03-31T09:33:42.000+0200}, author = {Bouwens, R. J. and Illingworth, G. D. and Oesch, P. A. and Caruana, J. and Holwerda, B. and Smit, R. and Wilkins, S.}, biburl = {https://www.bibsonomy.org/bibtex/2a94020a4c2ec1bb554b04546f46df479/miki}, description = {[1503.08228] Cosmic Reionization after Planck: The Derived Growth of the Ionizing Background now matches the Growth of the Galaxy UV Luminosity Density}, interhash = {1b88588320fae3bc6462be7f7f294227}, intrahash = {a94020a4c2ec1bb554b04546f46df479}, keywords = {galaxy high-z reionisation}, note = {cite arxiv:1503.08228Comment: 16 pages, 10 figures, 3 tables, submitted to the Astrophysical Journal, Figure 6 shows the main result of the paper, Table 1 includes a compilation of the many key constraints on the ionisation state of the universe at z>6}, timestamp = {2015-03-31T09:33:42.000+0200}, title = {Cosmic Reionization after Planck: The Derived Growth of the Ionizing Background now matches the Growth of the Galaxy UV Luminosity Density}, url = {http://arxiv.org/abs/1503.08228}, year = 2015 }