Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000hst..prop.8698m&link_type=abstract
HST Proposal ID #8698
Astronomy and Astrophysics
Astrophysics
Hst Proposal Id #8698 Stellar Populations
Scientific paper
The nature of dark matter is one of the key astrophysical questions of the day. The existence of dark matter and its dynamical dominance in the outer parts of our Galaxy and spiral galaxies with flat rotation curves is well established. The MACHO project has identified half of the Milky Way's dark matter with stellar objects of 0.5 M_sun, probably white dwarfs. But the location of the microlensing in the halo is disputed. Ibata et al {astroph-9908270} have detected two candidate halo white dwarfs of L/L_sun 10^-5 in the Hubble Deep Field with 25 +/- 5 mas/year proper motions. They argue that this could be the missing mass. We propose to make second epoch observations of 20 WFPC2 fields in the Groth parallel program. If Ibata et al are correct, we expect to see five times the number of white dwarfs, at half the distance, with twice the proper motions, and three times the time baseline. The angular shift of these objects will be 300 mas, readily detected with WFPC2. In addition, the detected objects will be bright enough for low dispersion spectroscopy with large telescopes. If we confirm the Ibata et al result, quantitative constraints will be put on the fraction of the Galaxy's missing mass in this new stellar population.
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