CII is one of the brightest emission lines from star-forming galaxies and is an excellent tracer for star formation. Recent work measured the CII emission line amplitude for redshifts 2<z<3.2 by cross-correlating Planck High Frequency Instrument emission maps with tracers of overdensity from the Baryon Oscillation Spectroscopic Sky Survey, finding ICII=6.6−4.8+5.0×104 Jy/sr at 95% confidence. In this paper, we present a refinement of this earlier work by improving the mask weighting in each of the Planck bands and the precision in the covariance matrix. We report a detection of excess emission in the 545 GHz Planck band separate from the cosmic infrared background (CIB) present in the 353-857 GHz Planck bands. This excess is consistent with redshifted CII emission, in which case we report bCIIICII=2.0−1.1+1.2×105 Jy/sr at 95% confidence, which strongly favors many collisional excitation models of CII emission. Our detection shows strong evidence for a model with a non-zero CII parameter, though line intensity mapping observations at high spectral resolution will be needed to confirm this result.
@article{arxiv.1904.01180,
title = {Evidence for CII diffuse line emission at redshift $z\sim2.6$},
author = {Shengqi Yang and Anthony R. Pullen and Eric R. Switzer},
journal= {arXiv preprint arXiv:1904.01180},
year = {2019}
}