Returning magnetic flux in sunspot penumbrae

We study the presence of reversed polarity magnetic flux in sunspot penumbra. We applied a new regularized method to deconvolve spectropolarimetric data observed with the spectropolarimeter SP onboard Hinode. The new regularization is based on a principal component decomposition of the Stokes profiles. The resulting Stokes profiles were inverted to infer the magnetic field vector using SIR. We find, for the first time, reversed polarity fields at the border of many bright penumbral filaments in the whole penumbra.Comment: 5 pages, 5 figures, accepted for publication in A&A Letter

Spatial deconvolution of spectropolarimetric data: an application to quiet Sun magnetic elements

Observations of the Sun from the Earth are always limited by the presence of the atmosphere, which strongly disturbs the images. A solution to this problem is to place the telescopes in space satellites, which produce observations without any (or limited) atmospheric aberrations. However, even though the images from space are not affected by atmospheric seeing, the optical properties of the instruments still limit the observations. In the case of diffraction limited observations, the PSF establishes the maximum allowed spatial resolution, defined as the distance between two nearby structures that can be properly distinguished. In addition, the shape of the PSF induce a dispersion of the light from different parts of the image, leading to what is commonly termed as stray light or dispersed light. This effect produces that light observed in a spatial location at the focal plane is a combination of the light emitted in the object at relatively distant spatial locations. We aim to correct the effect produced by the telescope's PSF using a deconvolution method, and we decided to apply the code on Hinode/SP quiet Sun observations. We analyze the validity of the deconvolution process with noisy data and we infer the physical properties of quiet Sun magnetic elements after the deconvolution process.Comment: 14 pages, 9 figure

Clear detection of dusty torus signatures in a Weak-Line Radio Galaxy: the case of PKS 0043-42

We report the clearest detection to date of dusty torus signatures in a Weak-Line Radio Galaxy (WLRG). The deep Spitzer InfraRed Spectrograph (IRS) rest-frame mid-infrared (MIR) spectrum of the WLRG PKS 0043-42 (z=0.116) shows a clear spectral turnover at wavelengths longer than ~20 micron suggestive of warm dust, as well as a 9.7 micron silicate absorption feature. In addition, the hard X-ray results, based on Chandra data, strongly support a picture in which PKS 0043-42 has a torus and accretion disc more typical of Strong-Line Radio Galaxies (SLRGs). The MIR and X-ray spectra are markedly different from those of other WLRGs at similar redshifts, and here we show that the former can be successfully fitted with clumpy torus models with parameters characteristic of Type-2 AGN tori: close to edge-on (i=74 deg) and relatively broad (torus angular width=60 deg), with an outer radius of 2 pc, hydrogen column density ~1.6x10^(23) cm^(-2), and AGN bolometric luminosity ~1.6x10^(44) erg s^(-1). The presence of a compact torus in PKS 0043-42 provides evidence that this WLRG is fuelled by cold, rather than hot, gas accretion. We suggest that WLRGs are a diverse population, and PKS 0043-42 may represent a type of radio galaxy in which the AGN activity has been recently re-triggered as a consequence of intermittent gas supply, or in which the covering factor of the Narrow-Line Region (NLR) clouds is relatively low.Comment: 7 pages, 6 figures, 1 table. Accepted by MNRA

Intragranitic locle golcl cleposits in the Tomiño area (Ponteveclra)

[Resumen] En este trabajo se describen las principales características de las mineralizaciones auríferas filonianas que aparecen en varios cuerpos graníticos sintectónicos en el área de Tomillo (SW de la provincia de Pontevedra), haciendo también referencia al contexto geológico en el que dichas mineralizaciones se presentan. Se trata de venas y filones de cuarzo con sulfuros (pirita, arsenopirita y calcopirita principalmente), con greisenización asociada, originados como consecuencia de un proceso neumatolítico-hidrotermal controlado por el sistema de fracturas de los granitos encajantes. Pueden diferenciarse cinco paragénesis consecutivas: postmagmática, de endogreisen, hidrotermal temprana, hidrotermal tardía y supergénica. El oro se presenta en forma de inclusiones microscópicas dentro de los sulfuros (principalmente en la calcopirita), que van aumentando en tamaño y proporciór a lo largo de las etapas sucesivas del proceso de mineralización.[Abstract] The main characteristics of lode gold deposits ocurring in sorne syntectonic granitic bodies in the Tomiño Area (SW of Pontevedra province) are described in this work. The geological context of this mineralization type is also referred to. The mineralizations consist of quartz-veins bearing sulphides (mainly pyrite, arsenopyrite and chalcopyrite), with associated greisenization in the wallrock, produced by a pneumatolytic-hydrothermal process that is controlled by the fracture system in the host granites. Five consecutive paragenesis can be distinguished: postmagmatic, endogreisen, early hydrothermal, late hydrothermal and supergene. Gold oeeurs as mieroseopie inelusions inside sulphides (mainly in ehalco-pyrite), inereasing in size and proportion along the sueeesive stages in the mineralization proeess

Model selection for spectro-polarimetric inversions

Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on objective reasons (for instance, the necessity to explain asymmetries in the Stokes profiles) but it is not clear what degree of complexity is needed. The lack of an objective way of comparing models has, sometimes, led to opposing views of the solar magnetism because the inferred physical scenarios are essentially different. We present the first quantitative model comparison based on the computation of the Bayesian evidence ratios for spectropolarimetric observations. Our results show that there is not a single model appropriate for all profiles simultaneously. Data with moderate signal-to-noise ratios favor models without gradients along the line-of-sight. If the observations shows clear circular and linear polarization signals above the noise level, models with gradients along the line are preferred. As a general rule, observations with large signal-to-noise ratios favor more complex models. We demonstrate that the evidence ratios correlate well with simple proxies. Therefore, we propose to calculate these proxies when carrying out standard least-squares inversions to allow for model comparison in the future.Comment: 16 pages, 2 figures, 8 tables, accepted for publication in Ap

Structure and mineralogy of a gold ore body of shear zone origin: the Fosas de Vila ore. La Coruña. Spain

[Abstract] This paper studies a shear zone containing a gold-bearing milonitic body, in which, evidences of several mining works are still visible. The geometry of the structure is described, as well as the different evolutive stages of the milonitic body and the mineralizations associated with them