SIMBAD references

Using the deepest and finest resolution images of the universe acquired with the Hubble Space Telescope and a similar image taken 7 yr later for the Great Observatories Origins Deep Survey, we have derived proper motions for the point sources in the Hubble Deep Field-North. Two faint blue objects, HDF 2234 and HDF 3072, are found to display significant proper motion, 10.0±2.5 and 15.5±3.8 mas/yr. Photometric distances and tangential velocities for these stars are consistent with disk white dwarfs located at ∼500 pc. The faint blue objects analyzed by Ibata et al. and Mendez & Minniti do not show any significant proper motion; they are not halo white dwarfs, and they do not contribute to the Galactic dark matter. These objects are likely to be distant active galactic nuclei.