Extended Data Fig. 1: Multiwavelength images of the CDF-S XT2 neighbourhood.

a, Merged Chandra 0.5–7-keV image including the entire 7-Ms CDF-S survey. b, Same as a, but excluding ObsID 16453. c, Chandra 0.5–7-keV image from ObsID 16453 alone. The large dashed circle marks the source region (r = 3.5″) for the extraction of light curves and spectra. The X-ray images in a–c are rendered in counts using the same linear scale, with pixel values ranging from 0 to 8. d, HST/CANDELS F160W image. In each panel, the small red circle marks the position and 1σ positional uncertainty of the source with XID_7Ms 330 reported in the 7-Ms CDF-S main catalogue¹⁷, while the cyan circle denotes that of the source with XID_4Ms 256 reported in the 4-Ms CDF-S main catalogue³⁸. The magenta numbers and crosses mark the object numbers of the six closest galaxies to CDF-S XT2 (see Extended Data Table 2) and their positions in the CANDELS F160W DR1 catalogue²², respectively. For clarity, the position of CDF-S XT2 is not annotated; it is slightly (about 0.3″) northeastern to that of XID_7Ms 330.