[CII] emission in z ~ 6 strongly lensed, star-forming galaxies

Understand

The far-infrared fine-structure line [CII] at 1900.5\,GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star-formation in very high-redshift galaxies.

• However, recent results for galaxies at $z>6$ have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimeter galaxies.
• We report the results of ALMA observations of two lensed, star-forming galaxies at $z = 6.029$ and $z=6.703$.
• The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M$_\odot$ yr$^{-1}$ and magnification of $\mu = 11.4\pm1.9$) shows a line detection with $L_{\rm [CII]} = 8.9\times10^{6}$ L$_\odot$, making it the lowest $L_{\rm [CII]}$ detection at $z>6$.