Search

The existence of life is one of the most fundamental problems of astrophysics. The intriguing existence of progressively complex and apparently improbable living beings should be a general tendency of life in the Universe. We are looking for general physical laws governing the growth of complexity in any astrophysical environment. We posit the existence of a vital scalar field. This scalar is sensitive to the gradient of the inverse of specific entropy, such that its distribution tends to very high values in the interior of living beings. Besides the classical mutations, vital field driven mutations only produce decrements of entropy. The field equations give rise to the existence of vital waves. This theory is able to deal with both the origin of life and the evolution of life. We show that the growth of complexity is accelerated by the vital field., Comment: 19 pages, 3 figures. Accepted for publication in Revista Mexicana de Astronom\'ia y Astrof\'isica

Several cosmic-ray observatories have provided a high accuracy map of the sky at TeV--PeV energies. The data reveals an O(0.1%) deficit from north galactic directions that peaks at 10 TeV and then evolves with the energy, together with other anisotropies at smaller angular scales. Using Boltzmann's equation we derive expressions for the cosmic-ray flux that fit most of these features. The anisotropies depend on the local interstellar magnetic field B_{IS}, on the average galactic field B_{R} in our vicinity, and on the distribution of dominant cosmic-ray sources. We show that the initial dipole anisotropy along B_{IS} can be modulated by changes in the global cosmic ray wind, and that a variation in the dipole direction would imply a given radius of coherence for B_{IS}. We also show that small and medium-scale anisotropies may appear when the full-sky anisotropy finds a turbulence acting as a magnetic lens., Comment: 14 pages

Following the model of magnetically supported rotation of spiral galaxies, the inner disk rotation is dominated by gravity but magnetism is not negligible at radii where the rotation curve becomes flat, and indeed becomes dominant at very large radii. Values of the order of 1 $\mu$G, or even less, produce a centripetal force when the absolute value of the slope of the curve [$B_\phi$, R] (azimuthal field strength versus radius) is less than $R^{-1}$. The $R^{-1}$-profile is called the critical profile. From this hypothesis, the following is to be expected: at large radii, a ``subcritical'' profile (slope flatter than $R^{-1}$); at still larger radii a $B_\phi$-profile becoming asymptotically critical as the density becomes asymptotically vanishing. Recent observations of magnetic fields in NGC 6946 and the Milky Way are in very good agreement with these predictions. This magnetic alternative requires neither galactic dark matter (DM) nor modification of fundamental laws of physics, but it is not in conflict with these hypotheses, especially with the existence of cosmological cold dark matter (CDM)., Comment: 11 pages, 2 figures, accepted for publication in Astron. Astrophys

We present a first study of truncation of the stellar disks of spiral galaxies in the near infrared. Observations of NGC4013, NGC4217, NGC6504 and NGC5981 were made with the CAIN NIR camera on the CST in Tenerife. This wavelength range provides the best description of the phenomenon, not only because extinction effects are minimized, but also because the distribution of the old stellar population is directly obtained. The four galaxies are edge-on and an inversion method was developed to obtain the deprojected profiles. We did not assume any model of the different galactic components. The ``truncation curve'', i.e. T(R)= mu(R)- mu_{D}(R), where mu is the actual surface brightness in mag/arcsec^2 and mu_{D} the exponential disk surface brightness, has been obtained with unprecedented precision. It is suggested that T(R) is proportional to (R_{t}-R)^{-1}, where R_{t} is the truncation radius, i.e. the radius beyond which no star is observed., Comment: 16 pages, 7 figures, accepted in Astronomy and Astrophysics

We review the topic of rotation curves of spiral galaxies emphasizing the standard interpretation as evidence for the existence of dark matter halos. Galaxies other than spirals and late-type dwarfs may also possess great amounts of dark matter, and therefore ellipticals, dwarf spirals, lenticulars and polar ring galaxies are also considered. Furthermore, other methods for determining galactic dark matter, such as those provided by binaries, satellites or globular clusters, have to be included. Cold dark matter hierarchical models constitute the standard way to explain rotation curves, and thus the problem becomes just one aspect of a more general theory explaining structure and galaxy formation. Alternative theories also are included. In the magnetic model, rotation curves could also be a particular aspect of the whole history of cosmic magnetism during different epochs of the Universe. Modifications of Newtonian Dynamics provide another interesting possibility which is discussed here., Comment: 116 pages, 23 figures. Accepted in Fundamentals of Cosmic Physics