Recent observations of the rotation curve of M31 show a rise of the outer part that cannot be understood in terms of standard dark matter models or perturbations of the galactic disk by M31?s satellites. Here, we propose an explanation of this dynamical feature based on the in?uence of the magnetic ?eld within the thin disk. We have considered standard mass models for the luminous mass distribution, a Navarro?Frenk?White model to describe the dark halo, and we have added up the contribution to the rotation curve of a magnetic ?eld in the disk, which is described by an axisymmetric pattern. Our conclusion is that a signi?cant improvement of the ?t in the outer part is obtained when magnetic effects are considered. The best-?t solution requires an amplitude of ?4 ?G with a weak radial dependence between 10 and 38 kpc.
Advertised on
References
(2010) The Astrophysical Journal Letters, Volume 723, Issue 1, pp. L44-L48
It may interest you
-
It’s been decades since the need to study other stars to understand the past, present and future of the Sun was realized. One important aspect that has been investigated is the magnetic activity of stars for which we cannot fully grasp the mechanisms involved. Indeed, the origin of stellar magnetic cycles or the dependence of the magnetic activity on the stellar properties are not completely understood. This knowledge improves not only our understanding of the physics involved in stellar evolution but also affects the study of the Sun to better predict high-energy events and the betterAdvertised on
-
WISEA J181006.18-101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as an extreme early-T subdwarf. However, methane--the characteristic molecule of the spectral class T--was not detected in the previous low-resolution spectrum. Constraining the metallicity--the abundance of elements heavier than helium-- of these cold objects has been a challenge. Using the 10.4 m Gran Telescopio Canarias, the largest optical-infrared telescope in the world, we collected a high-quality near-infrared intermediate-resolutionAdvertised on
-
The properties of blue supergiants are key for constraining the end of the main sequence phase, a phase during which massive stars spend most of their lifetimes. The lack of fast-rotating stars below 21.000K, a temperature around which stellar winds change in behaviour, has been proposed to be caused by enhanced mass-loss rates, which would spin down the star. Alternatively, the lack of fast-rotating stars may be the result of stars reaching the end of the main sequence. Here, we combine newly derived estimates of photospheric and wind parameters, wind terminal velocities from the literatureAdvertised on