Issue |
A&A
Volume 507, Number 2, November IV 2009
|
|
---|---|---|
Page(s) | 635 - 638 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/200912571 | |
Published online | 24 September 2009 |
Tully-Fisher relation, key to dark companion of baryonic matter
Institute for Advanced Studies in Basic Sciences (IASBS), PO Box 45195-1159, Zanjan, Iran e-mail: [sobouti;a.hasani;haghi]@iasbs.ac.ir
Received:
26
May
2009
Accepted:
20
August
2009
Rotation curves of spiral galaxies i) fall off
much less steeply than the Keplerian curves do; and ii) have
asymptotic speeds almost proportional to the fourth root of the mass
of the galaxy, the Tully-Fisher relation. These features alone are
sufficient for assigning a dark companion to the galaxy in an
unambiguous way. In regions outside a spherical system, we design a
spherically symmetric spacetime to accommodate these peculiarities. Gravitation emerges in excess of what the observable
matter can produce. We attribute the excess gravitation to a
hypothetical, dark, perfect fluid companion to the galaxy and resort
to the Tully-Fisher relation to deduce its density and pressure. The
dark density turns out to be proportional to the square root of the
mass of the galaxy and to fall off as . The dark equation of state is barrotropic. For the interior of
the configuration, we require the continuity of the total force
field at the boundary of the system. This enables us to determine
the size and the distribution of the interior dark density and
pressure in terms of the structure of the observable matter. The
formalism is nonlocal and nonlinear, and the density and pressure of
the dark matter at any spacetime point turn out to depend on certain
integrals of the baryonic matter over all or parts of the system in
a nonlinear manner.
Key words: gravitation / methods: numerical / galaxies: spiral / cosmology: dark matter
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.