M 51 EOs (grey dots) overlayed on a Digitized Sky Survey 2 (DSS2) image of M 51. The grey lines indicate the size of the HST mosaic of 6 ACS images used by Hwang & Lee (2008) to find EOs in M 51. The black circles indicate projected distances from M 51 of 10, 20, 50, and 100 kpc. For comparison, the projected position of the Milky Way EOs, if the Milky Way would be seen face-on at the distance and the position of M 51, are added as black crosses.