Strong [CII] emission at high redshift

TL;DR

This paper reports the first detection of strong [CII] emission in a high-redshift galaxy with lower infrared luminosity, suggesting an enhancement of [CII] emission at high redshift compared to local galaxies, which could improve high-z galaxy detection.

Contribution

First detection of [CII] line in a high-redshift galaxy with L_FIR < 10^13 L_sun, revealing enhanced [CII] emission relative to local galaxies of similar luminosity.

Findings

[CII] emission is significantly stronger than in previous high-z observations.

The L_[CII]/L_FIR ratio is higher than in local galaxies with similar IR luminosity.

High-z galaxies may have different physical conditions than local counterparts.

Abstract

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.