ABSTRACT We propose to use the flux variability of lensed quasar images induced by gravitational microlensing to measure the transverse peculiar velocity of lens galaxies over a wide range of ...redshift. Microlensing variability is caused by the motions of the observer, the lens galaxy (including the motion of the stars within the galaxy), and the source. Hence, its frequency is directly related to the galaxy's transverse peculiar velocity. The idea is to count time-event rates (e.g., peak or caustic crossing rates) in the observed microlensing light curves of lensed quasars that can be compared with model predictions for different values of the transverse peculiar velocity. To compensate for the large timescale of microlensing variability, we propose to count and model the number of events in an ensemble of gravitational lenses. We develop the methodology to achieve this goal and apply it to an ensemble of 17 lensed quasar systems. In spite of the shortcomings of the available data, we have obtained tentative estimates of the peculiar velocity dispersion of lens galaxies at z ∼ 0.5, . Scaling at zero redshift, we derive , consistent with peculiar motions of nearby galaxies and with recent N-body nonlinear reconstructions of the Local Universe based on ΛCDM. We analyze the different sources of uncertainty of the method and find that for the present ensemble of 17 lensed systems the error is dominated by Poisson noise, but that for larger ensembles the impact of the uncertainty on the average stellar mass may be significant.
We use the Wilkinson Microwave Anisotropy Probe (WMAP) 9th-year foreground reduced data at 33, 41 and 61 GHz to derive a Faraday rotation at map and at angular power spectrum levels taking into ...account their observational errors. A processing mask provided by WMAP is used to avoid contamination from the disc of our Galaxy and local spurs. We have found a Faraday rotation component at both, map and power spectrum levels. The lack of correlation of the Faraday rotation with Galactic Faraday rotation, synchrotron and dust polarization from our Galaxy or with cosmic microwave background anisotropies or lensing suggests that it could be originated at reionization (ℓ ≲ 12). Even if the detected Faraday rotation signal is weak, the present study could contribute to establish magnetic fields strengths of B
0 ∼ 10−8 G at reionization.
Context. The knowledge of the regular (large scale) component of the Galactic magnetic field gives important information about the structure and dynamics of the Milky Way, and also constitutes a ...basic tool to determine cosmic ray trajectories. It can also provide clear windows where primordial magnetic fields could be detected. Aims. We aim to obtain the regular (large scale) pattern of the magnetic field distribution of the Milky Way that better fits the polarized synchrotron emission as seen by the WMAP satellite in the 5 years data at 22 GHz. Methods. We have done a systematic study of a number of Galactic magnetic field models: axisymmetric (with and without radial dependence on the field strength), bisymmetric (with and without radial dependence), logarithmic spiral arms, concentric circular rings with reversals and bi-toroidal. We have explored the parameter space defining each of these models using a grid-based approach. In total, more than one million models were computed. The model selection was done using a Bayesian approach. For each model, the posterior distributions were obtained and marginalized over the unwanted parameters to obtain the marginal (one-parameter) probability distribution functions. Results. In general, axisymmetric models provide a better description of the halo component, although with regard to their goodness-of-fit, the other models cannot be rejected. In the case of the disk component, the analysis is not very sensitive for obtaining the disk large-scale structure, because of the effective available area (less than 8% of the whole map and less than 40% of the disk). Nevertheless, within a given family of models, the best-fit parameters are compatible with those found in the literature. Conclusions. The family of models that better describes the polarized synchrotron halo emission is the axisymmetric one, with magnetic spiral arms with a pitch angle of ≈24°, and a strong vertical field of 1 μG at z ≈ 1 kpc. When a radial variation is fitted, models require fast variations.
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 influence of the magnetic field 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 field in the disk, which is described by an axisymmetric pattern. Our conclusion is that a significant improvement of the fit in the outer part is obtained when magnetic effects are considered. The best-fit solution requires an amplitude of ~4 Delta *mG with a weak radial dependence between 10 and 38 kpc.
Cosmic magnetic lenses Battaner, E.; Castellano, J.; Masip, M.
Astronomy and astrophysics (Berlin),
03/2011, Letnik:
527
Journal Article
Recenzirano
Odprti dostop
Aims. Magnetic fields play a critical role in the propagation of charged cosmic rays. We investigate here whether some particular field configurations supported by various astrophysical objects ...produce images on cosmic ray maps. Methods. We consider a simple configuration, namely a constant azimuthal field in a disk-like object, which we identify as a cosmic magnetic lens. Such a configuration is typical of most spiral galaxies, and we hypothetize that it can also appear on smaller or larger scales. Results. We show that the magnetic lens deflects cosmic rays in a regular geometrical pattern, very much like a gravitational lens deflects light but with some interesting differences. In particular, the lens acts effectively only in a definite region of the cosmic-ray spectrum, and it can be convergent or divergent depending on the (clockwise or counterclockwise) direction of the magnetic field and the (positive or negative) electric charge of the cosmic ray. We find that the image of a point-like monochromatic source may be one, two, or four points depending on the relative positions of the source, the observer, and the center of the lens. For a perfect alignment and a lens in the orthogonal plane, the image becomes a ring. We also show that the presence of a lens could introduce low-scale fluctuations and matter-antimatter asymmetries in the fluxes from distant sources. Conclusions. The concept of cosmic magnetic lens that we introduce here may be useful for interpreting possible patterns observed in the cosmic ray flux at different energies.
Context. Warps occurring in galactic discs have been studied extensively in HI and in the optical, but rarely in the near-infrared (NIR) bands that trace the older stellar populations. Aims. We ...provide NIR data of nearby edge-on galaxies, combined with optical observations, for direct comparison of the properties of galactic warps as a function of wavelength, and calculate warp curves for each galaxy and obtain the characteristic warp parameters. We discuss these properties as possible constraints to the different mechanisms that have been proposed for the development and persistence of galactic warps. Methods. We observed 20 galaxies that were selected from a statistically complete diameter-limited subsample of edge-on disc galaxies. We used the Cerro Tololo Infrared Imager (CIRIM) at the CTIO 1.5 m Ritchey-Chretien telescope to acquire the NIR data. We used the 1.54 m Danish and 0.92 m Dutch telescopes at the European Southern Observatory's La Silla site for our optical observations. Results. Our results show that 13 of our 20 sample galaxies are warped, with the warp more pronounced in the optical than at NIR wavelengths. In the remaining seven galaxies, no warp is apparent within the limitations of our automated detection method. The transition between the unperturbed inner disc and the outer, warped region is rather abrupt. S0 galaxies exhibit very small or no warps. The magnetic model remains one of a number of interesting formation scenarios.
We investigate the use of the rest-frame 24 mu m luminosity as an indicator of the star formation rate (SFR) in galaxies with different metallicities by comparing it to the (extinction-corrected) H ...alpha luminosity. We carry out this analysis in two steps: First, we compare the emission from H II regions in different galaxies with metallicities between 12 + log(O/H) = 8.1 and 8.9. We find that the 24 mu m and the extinction-corrected H alpha luminosities from individual H II regions follow the same correlation for all galaxies, independent of their metallicity. Second, the role of metallicity is explored further for the integrated luminosity in a sample of galaxies with metallicities in the range of 12 + log (O/H) = 7.2-9.1. For this sample we compare the 24 mu m and H alpha luminosities integrated over the entire galaxies and find a lack of the 24 mu m emission for a given H alpha luminosity for low-metallicity objects, likely reflecting a low dust content. These results suggest that the 24 mu m luminosity is a good metallicity-independent tracer for the SFR in individual H II regions. On the other hand, metallicity has to be taken into account when using the 24 mu m luminosity as a tracer for the SFR of entire galaxies.
The study of the disk rotation curve of our Galaxy at large distances provides an interesting scenario for us to test whether magnetic fields should be considered as a non-negligible dynamical ...ingredient. By assuming a bulge, an exponential disk for the stellar and gaseous distributions, and a dark halo and disk magnetic fields, we fit the rotation velocity of the Milky Way. In general, when the magnetic contribution is added to the dynamics, a better description of the rotation curve is obtained. Our main conclusion is that magnetic fields should be taken into account for the Milky Way dynamics. Azimuthal magnetic field strengths of B sub(varphi) ~ 2 mu G at distances of ~2 R sub(0)(16 kpc) are able to explain the rise-up for the rotation curve in the outer disk.
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.
The characteristic t(12;16)(q13;p11) chromosomal translocation, which leads to gene fusion that encodes the FUS-CHOP chimeric protein, is associated with human liposarcomas. The altered expression of ...FUS-CHOP has been implicated in a characteristic subgroup of human liposarcomas. We have introduced the FUS-CHOP transgene into the mouse genome in which the expression of the transgene is successfully driven by the elongation factor 1alpha (EF1alpha) promoter to all tissues. The consequent overexpression of FUS-CHOP results in most of the symptoms of human liposarcomas, including the presence of lipoblasts with round nuclei, accumulation of intracellular lipid, induction of adipocyte-specific genes and a concordant block in the differentiation program. We have demonstrated that liposarcomas in the FUS-CHOP transgenic mice express high levels of the adipocyte regulatory protein PPARgamma, whereas it is not expressed in embryonic fibroblasts from these animals following induction to differentiation toward the adipocyte lineage, indicating that the in vitro system does not really reflect the in vivo situation and the developmental defect is downstream of PPARgamma expression. No tumors of other tissues were found in these transgenic mice despite widespread activity of the EF1alpha promoter. This establishes FUS-CHOP overexpression as a key determinant of human liposarcomas and provide the first in vivo evidence for a link between a fusion gene created by a chromosomal translocation and a solid tumor.
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