This paper discusses a new model for galactic dark matter by combining an
anisotropic pressure field corresponding to normal matter and a quintessence
dark energy field having a characteristic parameter ωq such that
−1<ωq<−31. Stable stellar orbits together with an attractive
gravity exist only if ωq is extremely close to −31, a result
consistent with the special case studied by Guzman et al. (2003). Less
exceptional forms of quintessence dark energy do not yield the desired stable
orbits and are therefore unsuitable for modeling dark matter.Comment: 12 pages, 1 figur