Imprint of First Stars Era in the Cosmic Infrared Background Fluctuations

We present the latest results on Cosmic Infrared Background (CIB) fluctuations from early epochs from deep Spitzer data. The results show the existence of significant CIB fluctuations at the IRAC wavelengths (3.6 to 8 μm) which remain after removing galaxies down to very faint levels. These fluctuations must arise from populations with a significant clustering component, but only low levels of the shot noise. There are no correlations between the source-subtracted IRAC maps and the corresponding fields observed with the HST ACS at optical wavelengths. Taken together, these data imply that 1) the sources producing the CIB fluctuations are individually faint with S_ν < a few nJy at 3.6 and 4.5 μm 2) have different clustering pattern than the more recent galaxy populations; 3) are located within the first 0.7 Gyr (unless these fluctuations can somehow be produced by - so far unobserved - local galaxies of extremely low luminosity and with the unusual for local populations clustering pattern), 4) produce contribution to the net CIB flux of at least 1-2 nW m_-2 sr_-1 at 3.6 and 4.5 μm and must have mass-to-light ratio significantly below the present-day populations, and 5) they have angular density of ~ a few per arcsec² and are in the confusion of the present day instruments, but can be individually observable with JWST.