Science Highlight

As part of the ongoing ALMA large program REBELS (Reionization-Era Bright Emission Line Survey), 40 UV-luminous primary targets were observed at z > 6.5. Among these targets are REBELS-12 and REBELS-29. In their recent paper, Fudamoto and colleagues report two additional emission line neighbours found after inspecting the ALMA data cube of these two sources.

The images on the left show [CII] 158 µm line and dust emission detections for (a) the REBELS-29 field at z∼6.68 and (b) the REBELS-12 field at z∼7.35. Background images are HST F140W and VIDEO J-band, respectively. White horizontal bars correspond to 10 proper kpc. Solid red and light blue contours show 2σ to 5σ levels (and −5σ to −2σ for dashed contours) for the continuum and [CII] moment-0 maps, respectively. The continuum subtracted [CII] spectra are shown at the native velocity resolution of 20 km/s. The two sources REBELS-29-2 and REBELS-12-2 were found serendipitously as companions to the central, UV-luminous targets, with emission lines at almost exactly the same frequencies as the central targets, accompanied with dust continuum emission at the same location. Their spatial and spectral proximity, and absence in optical/NIR images confirms these companions as unexpected, dusty star forming sources in the epoch of reionization.