Roche lobe sizes in deep-MOND gravity

Free access article

Issue		A&A Volume 444, Number 2, December III 2005


Page(s)		L25 - L28
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:200500200

A&A 444, L25-L28 (2005)
DOI: 10.1051/0004-6361:200500200

Letter

Roche lobe sizes in deep-MOND gravity

Hong Sheng Zhao

SUPA, School of Physics and Astronomy, University of St Andrews, KY16 9SS, Fife, UK

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
e-mail: hz4@st-and.ac.uk

(Received 3 May 2005 / Accepted 7 October 2005 )

Abstract
MOdified Newtonian Dynamics survived the test over two decades, fitting the ups and downs of a variety of galaxy velocity curves without fine tuning (Sanders & McGaugh 2002, ARA&A, 40, 263). MOND is also evolving from an empirical to a decent theory respecting fundamental physics after Bekenstein (2004, Phys. Rev. D, 70, 3509) showed that lensing and Hubble expansion can be modeled rigourously in a Modified Relativity. However, many properties of MOND are obscured by its non-linear Poisson's equation. Here we study the effect of tides for a binary stellar system or a baryonic satellite-host galaxy system. We show that the Roche lobe is more squashed than the Newtonian case due to the anisotropic dilation effect in deep-MOND. We prove analytically that the Roche lobe volume scales linearly with the "true" baryonic mass ratio in both Newtonian and deep-MOND regimes, insensitive to the modification to the inertia mass. Hence accurate Roche radii of satellites can break the degeneracy of MOND and dark matter theory. Globular clusters and dwarf galaxies of comparable luminosities and distances show a factor of ten scatter in limiting radii; this is difficult to explain in any "mass-tracing-light" universe.

Key words: dark matter -- galaxy kinematics and dynamics -- gravitation -- galaxies: dwarf -- globular clusters

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.