Strong [CII] emission at high redshift

Abstract

We report the detection of the [Cii]157.74 μm 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 < 10¹³~L_⊙ at high redshift. The line is much stronger than 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 with the same infrared luminosity. This finding may result from selection effects of the few current observations of [Cii] at high redshift and, in particular, from non detections that may not have 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 than for their local counterparts. Regardless of the physical origin of the trend, this effect would increase the potential of the [Cii]158 μm line to search and characterize high-z sources.

Based on observations made with ESO telescope APEX, under program ID E-082.B-0692A-2008.

Appendix A is only available in electronic form at http://www.aanda.org