Event

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 I_CII=6.6^{+5.0}_{-4.8}*10^4 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 b_CII*I_CII =2.0^{+1.2}_{-1.1}*10^5 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. We will apply this cross-correlating strategy in EXCLAIM, a future intensity mapping survey that aims to measure the integrated CO and CII emission in 0<z<3.5, to probe the star formation rate decline puzzle.