Orateur
Dr
Luis Acedo
(Instituto de Matemática Multidisciplinar, Universidad Politécnica de Valencia)
Description
In 1983 Milgrom proposed an alternative explanation for the anomalous rotation of galaxies based upon a modification of Newtonian dynamics for small accelerations (MOND theory) [1] . A careful analysis of the rotation curves revealed that the effect of the supposed dark matter seems to activate only when the orbital acceleration is smaller than 2x10^{-8} cm s^{-2}.
MOND theory still challenges the Dark Matter community because simulations of cold dark matter (CDM) accretion favour the formation of halos with a cusp at the center of the galaxies (Via Lactea II [2]). The calculations of galactic density profiles from the rotation curves contradict the prediction of an halo with a peak at the center of galaxies. This phenomenon is related with Milgrom's law because a galactic core almost free from DM will imply that there exists a critical orbit separating the inner regions of the galaxy, where rotation behaviour can be deduced from the observed mass, and the outer regions where DM must be invoked to explain the discrepancy.
We show that this problem is overcome in a Warm Dark Matter theory for sterile neutrinos with a mass around 3 keV [3]. These particle behave as collisionless Vlasov particles with a primordial typical velocity around 330 km s^{-1} and, consequently, they evaporated from galactic cores and reorganized in halos with a cusp at a finite distance from the galactic center (in contrast with Cold Dark Matter simulations which predict a cusp at the center of galaxies).
[1] M. Milgrom, A modification of the Newtonian dynamics as a possible alternative to the hidden mass hypothesis, Astrophysical Journal 270 (1983) 365; A modification of the Newtonian dynamics - Implications for galaxies, Astrophysical Journal 270 (1983) 371.
[2] M. Kuhlen et al., The Via Lactea INCITE simulation: galactic dark matter substructure at high resolution, J. Phys. Conf. Ser. 125:012008 (2008), arXiv 0810.3614.
[3] L. Acedo, A WDM for the evolution of Galactic Halos, JCAP07 (2009) 037.
Author
Dr
Luis Acedo
(Instituto de Matemática Multidisciplinar, Universidad Politécnica de Valencia)
