A CENSUS OF STAR-FORMING GALAXIES IN THEZ∼ 9-10 UNIVERSE BASED ONHST+SPITZEROBSERVATIONS OVER 19 CLASH CLUSTERS: THREE CANDIDATEZ∼ 9-10 GALAXIES AND IMPROVED CONSTRAINTS ON THE STAR FORMATION RATE DENSITY ATZ∼ 9.2

Considering light-matter interactions in the Friedmann equations

Recent observations indicate that the Universe is not transparent but partially opaque due to absorption of light by ambient cosmic dust. This implies that the Friedmann equations valid for the transparent universe must be modified for the opaque universe. This paper studies a scenario in which the opacity rises with redshift. In this case, the light–matter interactions become important, because cosmic opacity produces radiation pressure that counterbalances gravitational forces. The presented theoretical model assumes the Universe is expanding according to the standard FLRW metric but with the scale factor a(t) depending on both types of forces: gravity as well as radiation pressure. The modified Friedmann equations predict a cyclic expansion/contraction evolution of the Universe within a limited range of scale factors with no initial singularity. The model avoids dark energy and removes some other tensions of the standard cosmological model. The paper demonstrates that considering light–matter interactions in cosmic dynamics is crucial and can lead to new cosmological models essentially different from the standard ΛCDM model. This emphasizes the necessity of new observations and studies of cosmic opacity and cosmic dust at high redshifts for more realistic modelling of the evolution of the Universe.

Ultraviolet luminosity density of the universe during the epoch of reionization

The spatial fluctuations of the extragalactic background light trace the total emission from all stars and galaxies in the Universe. A multiwavelength study can be used to measure the integrated emission from first galaxies during reionization when the Universe was about 500 million years old. Here we report arcmin-scale spatial fluctuations in one of the deepest sky surveys with the Hubble Space Telescope in five wavebands between 0.6 and 1.6 μm. We model-fit the angular power spectra of intensity fluctuation measurements to find the ultraviolet luminosity density of galaxies at redshifts greater than 8 to be . This level of integrated light emission allows for a significant surface density of fainter primeval galaxies that are below the point-source detection level in current surveys.

The luminosity of ultraviolet light emitted by the first galaxies in the universe traces the formation and evolution of stars and galaxies which led to the epoch of reionization. Here the authors use data from the Hubble Space Telescope and through a model provide a bound for the total luminosity.