1,865 research outputs found

    Deconstructing double-barred galaxies in 2D and 3D. II. Two distinct groups of inner bars

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    The intrinsic photometric properties of inner and outer stellar bars within 17 double-barred galaxies are thoroughly studied through a photometric analysis consisting of: i) two-dimensional multi-component photometric decompositions, and ii) three-dimensional statistical deprojections for measuring the thickening of bars, thus retrieving their 3D shape. The results are compared with previous measurements obtained with the widely used analysis of integrated light. Large-scale bars in single- and double-barred systems show similar sizes, and inner bars may be longer than outer bars in different galaxies. We find two distinct groups of inner bars attending to their in-plane length and ellipticity, resulting in a bimodal behaviour for the inner/outer bar length ratio. Such bimodality is related neither to the properties of the host galaxy nor the dominant bulge, and it does not show a counterpart in the dimension off the disc plane. The group of long inner bars lays at the lower end of the outer bar length vs. ellipticity correlation, whereas the short inner bars are out of that relation. We suggest that this behaviour could be due to either a different nature of the inner discs from which the inner bars are dynamically formed, or a different assembly stage for the inner bars. This last possibility would imply that the dynamical assembly of inner bars is a slow process taking several Gyr to happen. We have also explored whether all large-scale bars are prone to develop an inner bar at some stage of their lives, possibility we cannot fully confirm or discard.Comment: 14 pages, 8 figures, 1 table. Accepted for publication in MNRA

    On the nature of some SGRs and AXPs as rotation-powered neutron stars

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    We investigate the possibility that some SGRs/AXPs could be canonical rotation-powered pulsars using realistic NS structure parameters instead of fiducial values. We show that realistic NS parameters lowers the estimated value of the magnetic field and radiation efficiency, LX/E˙rotL_X/\dot{E}_{\rm rot}, with respect to estimates based on fiducial NS parameters. We show that nine SGRs/AXPs can be described as canonical pulsars driven by the NS rotational energy, for LXL_X computed in the soft (2--10~keV) X-ray band. We compute the range of NS masses for which LX/E˙rot<1L_X/\dot{E}_{\rm rot}<1. We discuss the observed hard X-ray emission in three sources of the group of nine potentially rotation-powered NSs. This additional hard X-ray component dominates over the soft one leading to LX/E˙rot>1L_X/\dot{E}_{\rm rot}>1 in two of them. We show that 9 SGRs/AXPs can be rotation-powered NSs if we analyze their X-ray luminosity in the soft 2--10~keV band. Interestingly, four of them show radio emission and six have been associated with supernova remnants (including Swift J1834.9-0846 the first SGR observed with a surrounding wind nebula). These observations give additional support to our results of a natural explanation of these sources in terms of ordinary pulsars. Including the hard X-ray emission observed in three sources of the group of potential rotation-powered NSs, this number of sources with LX/E˙rot<1L_X/\dot{E}_{\rm rot}<1 becomes seven. It remains open to verification 1) the accuracy of the estimated distances and 2) the possible contribution of the associated supernova remnants to the hard X-ray emission.Comment: 11 pages, 14 figures, to appear in A&

    Geodesic Deviation Equation in Bianchi Cosmologies

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    We present the Geodesic Deviation Equation (GDE) for the Friedmann-Robertson-Walker(FRW) universe and we compare it with the equation for Bianchi type I model. We justify consider this cosmological model due to the recent importance the Bianchi Models have as alternative models in cosmology. The main property of these models, solutions of Einstein Field Equations (EFE) is that they are homogeneous as the FRW model but they are not isotropic. We can see this because they have a non-null Weyl tensor in the GDE.Comment: Submitted to Journal of Physics: Conference Series (JPCS), ERE200

    La regulación jurídica de la calidad del agua en la provincia de Buenos Aires, Argentina: tensiones y variedad de criterios

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    El artículo analiza la regulación jurídica de la calidad del agua en la provincia de Buenos Aires. La calidad del agua reviste un papel crítico por la incidencia que tiene en la salud de la población y las condiciones de vida digna. Su prestación mediante el servicio público es la forma más segura de acceso y reduce la explotación de los acuíferos por parte de particulares de forma directa. La selección de la provincia como caso de estudio se vincula con dos motivos: por un lado, la presencia de distintas empresas que prestan el servicio y un entramado que atraviesa regulaciones de la nación y la provincia; y, por otro, la jurisprudencia que ha tenido lugar a partir de demandas por la calidad. El trabajo hace un análisis de la normativa vigente a nivel nacional y provincial de forma comparada, y de los fallos jurisprudenciales relativos a la calidad del agua. El análisis permite observar las tensiones que se presentan por la adecuación de valores de elementos contaminantes a las recomendaciones de la Organización Mundial de la Salud y la relevancia que ha tenido el Poder Judicial en materia de reconocimiento del derecho humano al agua
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