2000/07/28 by Katherine Freese, Freese, Katherine, Brian Fields +3
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0007444
contribution to: Sources and Detection of Dark Matter in the Universe, Marina del Rey, CA, February 2000
arxiv created 2000/07/28 · arxiv updated 2009/12/01
The nature of the dark matter in the Universe is one of the outstanding questions in astrophysics. In this talk, I address possible stellar baryonic contributions to the 50-90% of our Galaxy that is made of unknown dark matter. First I show that faint stars and brown dwarfs constitute only a few percent of the mass of the Galaxy. Next, I show that stellar remnants, including white dwarfs and neutron stars, are also insufficient in abundance to explain all the dark matter of the Galaxy. High energy gamma-rays observed in HEGRA data place the most robust constraints, ΩWD < 3 × 10-3 h-1, where h is the Hubble constant in units of 100 km s-1 Mpc-1. Overproduction of chemical abundances (carbon, nitrogen, and helium) provide the most stringent constraints, ΩWD < 2 × 10-4 h-1. Comparison with recent updates of microlensing data are also made. According to the gamma-ray limit, all Massive Compact Halo Objects seen by the experiments (Machos) can be white dwarfs if one takes the extreme numbers; however, from chemical overproduction limits, NOT all Machos can be white dwarfs. Comments on recent observations of the infrared background and of white dwarfs are also made. In conclusion, a nonbaryonic component in the Halo seems to be required.