Strong C+ emission in galaxies at z~1-2: Evidence for cold flow
  accretion powered star formation in the early Universe
  We have recently detected the [CII] 157.7 micron line in eight star forming
galaxies at redshifts 1 to 2 using the redshift(z) Early Universe Spectrometer
(ZEUS). Our sample targets star formation dominant sources detected in PAH
emission. This represents a significant addition to [CII] observations during
the epoch of peak star formation. We have augmented this survey with
observations of the [OI] 63 micron line and far infrared photometry from the
PACS and SPIRE Herschel instruments as well as Spitzer IRS spectra from the
literature showing PAH features. Our sources exhibit above average gas heating
efficiency, many with both [OI]/FIR and [CII]/FIR ~1% or more. The relatively
strong [CII] emission is consistent with our sources being dominated by star
formation powered PDRs, extending to kpc scales. We suggest that the star
formation mode in these systems follows a Schmidt-Kennicutt law similar to
local systems, but at a much higher rate due to molecular gas surface densities
10 to 100 times that of local star forming systems. The source of the high
molecular gas surface densities may be the infall of neutral gas from the
cosmic web. In addition to the high [CII]/FIR values, we also find high
[CII]/PAH ratios and, in at least one source, a cool dust temperature. This
source, SWIRE 4-5, bears a resemblance in these diagnostics to shocked regions
of Stephan's Quintet, suggesting that another mode of [CII] excitation in
addition to normal photoelectric heating may be contributing to the observed
[CII] line.
