Star formation and the interstellar medium in z>6 UV-luminous Lyman-break galaxies

Understand

We present Atacama Large Millimeter Array (ALMA) detections of atomic carbon line and dust continuum emission in two UV-luminous galaxies at redshift 6.

• The far-infrared (FIR) luminosities of these galaxies are substantially lower than similar starbursts at later cosmic epochs, indicating an evolution in the dust properties with redshift, in agreement with the evolution seen in ultraviolet (UV) attenuation by dust.
• The [CII] to FIR ratios are found to be higher than at low redshift showing that [CII] should be readily detectable by ALMA within the reionization epoch.
• One of the two galaxies shows a complex merger nature with the less massive component dominating the UV emission and the more massive component dominating the FIR line and continuum.