Strong [CII] emission at high redshift
  We report the detection of the [CII]157.74um fine-structure line in the
lensed galaxy BRI 0952-0115 at z=4.43, using the APEX telescope. This is the
first detection of the [CII] line in a source with L_FIR < 10^13 L_sun at high
redshift. The line is very strong compared to previous [CII] detections at
high-z (a factor of 5-8 higher in flux), partly due to the lensing
amplification. The L_[CII]/L_FIR ratio is 10^-2.9, which is higher than
observed in local galaxies with similar infrared luminosities. Together with
previous observations of [CII] at high redshift, our result suggests that the
[CII] emission in high redshift galaxies is enhanced relative to local galaxies
of the same infrared luminosity. This finding may result from selection effects
of the few current observations of [CII] at high redshift, and in particular
the fact that non detections may have not been published (although the few
published upper limits are still consistent with the [CII] enhancement
scenario). If the trend is confirmed with larger samples, it would indicate
that high-z galaxies are characterized by different physical conditions with
respect to their local counterparts. Regardless of the physical origin of the
trend, this effect would increase the potential of the [CII]158um line to
search and characterize high-z sources.
