A. Traficante

Publications (25) View all

• Article: Artifact removal for GLS map makers by means of post-processing.

  L Piazzo, D Ikhenaode, P Natoli, M Pestalozzi, F Piacentini, A Traficante
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  ABSTRACT: The quality of astrophysical images produced by means of the Generalised Least Square (GLS) approach may be degraded by the presence of artificial structures, obviously not present in the sky. This problem affects in different degrees all images produced by the instruments onboard the European Space Agency (ESA) Herschel satellite. In this paper we analyse these artifacts and introduce a method to remove them. The method is based on a post-processing of GLS image that estimates and removes the artifacts subtracting them from the original image. We find that the only drawback of this method is a slight increase of the background noise which, however, can be mitigated by detecting the artifacts and by performing the subtraction only where they are detected. The efficiency of the approach is demonstrated and quantified using simulated and real data.
  IEEE Transactions on Image Processing 05/2012; · 3.04 Impact Factor
• Source

  Available from: Glenn J. White

  Article: A 100 pc Elliptical and Twisted Ring of Cold and Dense Molecular Clouds Revealed by Herschel Around the Galactic Center

  S. Molinari, J. Bally, A. Noriega-Crespo, M. Compiègne, J. P. Bernard, D. Paradis, P. Martin, L. Testi, M. Barlow, T. Moore, [......], S. D. Lord, L. Morgan, F. Motte, F. Schuller, G. S. Stringfellow, J. C. Tan, M. A. Thompson, D. Ward-Thompson, G. White, and G. Umana
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  ABSTRACT: Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on board the Herschel satellite, reveal a ~3 × 107 M ☉ ring of dense and cold clouds orbiting the Galactic center. Using a simple toy model, an elliptical shape having semi-major axes of 100 and 60 pc is deduced. The major axis of this 100 pc ring is inclined by about 40° with respect to the plane of the sky and is oriented perpendicular to the major axes of the Galactic Bar. The 100 pc ring appears to trace the system of stable x 2 orbits predicted for the barred Galactic potential. Sgr A is displaced with respect to the geometrical center of symmetry of the ring. The ring is twisted and its morphology suggests a flattening ratio of 2 for the Galactic potential, which is in good agreement with the bulge flattening ratio derived from the 2MASS data.
  The Astrophysical Journal Letters 06/2011; 735(2):L33. · 5.53 Impact Factor
• Source

  Available from: Francesco Piacentini

  Article: The data reduction pipeline for the Hi-GAL survey

  A. Traficante, L. Calzoletti, M. Veneziani, B. Ali, G. de Gasperis, A. M. di Giorgio, D. Ikhenaode, S. Molinari, P. Natoli, M. Pestalozzi, S. Pezzuto, F. Piacentini, L. Piazzo, G. Polenta, E. Schisano
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  ABSTRACT: We present the data reduction pipeline for the Hi-GAL survey. Hi-GAL is a key project of the Herschel satellite which is mapping the inner part of the Galactic plane (|l| <= 70\cdot and |b| <= 1\cdot), using 2 PACS and 3 SPIRE frequency bands, from 70{\mu}m to 500{\mu}m. Our pipeline relies only partially on the Herschel Interactive Standard Environment (HIPE) and features several newly developed routines to perform data reduction, including accurate data culling, noise estimation and minimum variance map-making, the latter performed with the ROMAGAL algorithm, a deep modification of the ROMA code already tested on cosmological surveys. We discuss in depth the properties of the Hi-GAL Science Demonstration Phase (SDP) data.
  06/2011;
• Source

  Available from: Francesco Piacentini

  Article: A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center

  S. Molinari, J. Bally, A. Noriega-Crespo, M. Compiègne, J. -P. Bernard, D. Paradis, P Martin, L. Testi, M. Barlow, T. Moore, [......], S. D. Lord, L. Morgan, F. Motte, F. Schuller, G. S. Stringfellow, J. C. Tan, M. A. Thompson, D. Ward-Thompson, G White, G. Umana
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  ABSTRACT: Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on-board the Herschel satellite, reveal a 3x10^7 solar masses ring of dense and cold clouds orbiting the Galactic Center. Using a simple toy-model, an elliptical shape having semi-major axes of 100 and 60 parsecs is deduced. The major axis of this 100-pc ring is inclined by about 40 degrees with respect to the plane-of-the-sky and is oriented perpendicular to the major axes of the Galactic Bar. The 100-pc ring appears to trace the system of stable x_2 orbits predicted for the barred Galactic potential. Sgr A* is displaced with respect to the geometrical center of symmetry of the ring. The ring is twisted and its morphology suggests a flattening-ratio of 2 for the Galactic potential, which is in good agreement with the bulge flattening ratio derived from the 2MASS data.
  05/2011;
• Source

  Available from: Francesco Piacentini

  Article: Variations of the spectral index of dust emissivity from Hi-GAL observations of the Galactic plane

  D. Paradis, M. Veneziani, A. Noriega-Crespo, R. Paladini, F. Piacentini, J. -P. Bernard, P. de Bernardis, L. Calzoletti, F. Faustini, P Martin, S. Masi, L. Montier, P. Natoli, I. Ristorcelli, M. A. Thompson, A. Traficante, S. Molinari
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  ABSTRACT: Variations in the dust emissivity are critical for gas mass determinations derived from far-infrared observations, but also for separating dust foreground emission from the Cosmic Microwave Background (CMB). Hi-GAL observations allow us for the first time to study the dust emissivity variations in the inner regions of the Galactic plane at resolution below 1 degree. We present maps of the emissivity spectral index derived from the combined Herschel PACS 160 \mu m, SPIRE 250 \mu m, 350 \mu m, and 500 \mu m data, and the IRIS 100 \mu m data, and we analyze the spatial variations of the spectral index as a function of dust temperature and wavelength in the two Science Demonstration Phase Hi-GAL fields, centered at l=30{\deg} and l=59{\deg}. Applying two different methods, we determine both dust temperature and emissivity spectral index between 100 and 500 \mu m, at an angular resolution of 4'. Combining both fields, the results show variations of the emissivity spectral index in the range 1.8-2.6 for temperatures between 14 and 23 K. The median values of the spectral index are similar in both fields, i.e. 2.3 in the range 100-500 \mu m, while the median dust temperatures are equal to 19.1 K and 16.0 K in the l=30{\deg} and l=59{\deg} field, respectively. Statistically, we do not see any significant deviations in the spectra from a power law emissivity between 100 and 500 \mu m. We confirm the existence of an inverse correlation between the emissivity spectral index and dust temperature, found in previous analyses. Comment: A&A, accepted
  09/2010;