HST F555W image of corrected X-ray positions (solid red circles) and Chandra source detection error ellipses (dashed blue ellipses) of the ULXs. Since X-1 is not observed in the HST F555W filter, its position is shown on the F438W image. The numbers shown for the color bars are in units of electrons s⁻¹. Solid green circles within the error radii of X-5 indicate Gaia sources. All panels are to the same scale, with north up and east to the left.