Cross-correlation results. The red dashed line marks the maximum of the correlation, indicating the relative shift between the galaxy spectrum and the source spectrum. The green dashed line represents the median of the cross-correlation estimates. The gray shaded region denotes the ±1rms_MAD around the median. In the upper left corner, an 80×80 pixels zoom-in of the white-light image of the central region of UDG 11 is shown, with a red circle marking the specific source that is analyzed.