David Benisty Eduardo Geundelman and Ofer Lahav Edwin

David Benisty, Eduardo Geundelman and Ofer Lahav

Edwin Hubble (1889 – 1953)

§ The Local group includes the Milky Way galaxy, M 31 and several more small galaxies. • A good approximation for the LG considers only the MW and M 31. Phelps S. , Nusser A. , Desjacques V. , 2013, Ap. J, 775, 102 • How we can estimate the mass of the LG?

van der Marel R. et al. , 2012, Ap. J, 753, 8 §

The T. B. P action reads: The Center of Mass coordinate system: Yields:

§ We evaluate the measured distance of M 31 to obtain what should be the distance at t = 0, for different LG masses. Partridge, Ofer Lahav, Hoffman (MNRAS, 436, L 45, 2013) § The presence of the cosmological constant requires the mass of the LG to be 25% higher!!

§ Including angular momentum avoids singularities and make a possibility for post encounters. § Post encounters requires multiple masses, and the presence of the C. C becomes negligible.

§ Milgrom modifies Newton’s Second Law, instead of including additional matter: § For the Deep MOND regime: Mordehai Milgrom

The precession much differs from GR!

In Cosmology

D. Edmonds, D. Farrah, C. M. Ho, D. Minic, Y. J. Ng and T. Takeuchi, ``Testing MONDian Dark Matter with Galactic Rotation Curves, '' Astrophys. J. {bf 793}, 41 (2014). ]ar. Xiv: 1308. 3252 [astroph. CO. [[

Only after one post encounter MOND get the standard Baryonic matter as the Newtonian limit.

§ For short distances (up to 30 Mpc) only the dark energy contributes to the background. § Many papers that discussed about MOND – considered the dark matter twice.

§ Post Encounters require higher mass for the LG. § The cosmological constant requires higher mass. § MOND would be valid only if in the past M 31 and MW have done encounter. § A test for modified theories of gravity and screening mechanisms.