Faint Blue Objects on the Hubble Deep Field North and South as Possible Nearby Old Halo White Dwarfs*

摘要

Using data derived from the deepest and finest angular resolution images of the universe yet acquired by astronomers at optical wavelengths, with the Hubble Space Telescope (HST) in two postage-stamp sections of the sky, plus simple geometrical and scaling arguments, we demonstrate that the faint blue population of point-source objects detected in those two fields could actually be ancient halo white dwarfs at distances closer than about 2 kpc from the Sun. This finding has profound implications, as the mass density of the detected objects would account for about one-half of the missing dark matter in the Milky Way, thus solving one of the most controversial issues of modern astrophysics. The existence of these faint blue objects points to a very large mass locked into ancient halo white dwarfs. Our estimate indicates that they could account for as much as one-half of the dark matter in our Galaxy, confirming the suggestions of the MACHO microlensing experiment. Because of the importance of this discovery, deep follow-up observations with HST within the next two years would be needed to determine more accurately the kinematics (tangential motions) of these faint blue old white dwarfs.