Paradis, D. and Veneziani, M. and Noriega-Crespo, A. and Paladini, R. and Piacentini, F. and Bernard, J. P. and de Bernardis, P. and Calzoletti, L. and Faustini, F. and Martin, P. and Masi, S. and Montier, L. and Natoli, P. and Ristorcelli, I. and Thompson, M. A. and Traficante, A. and Molinari, S. (2010) Variations of the spectral index of dust emissivity from Hi-GAL observations of the Galactic plane. Astronomy and Astrophysics, 520 . L8. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20101109-094236545
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Context. 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°. Aims. We present maps of the emissivity spectral index derived from the combined Herschel PACS 160 μm, SPIRE 250 μm, 350 μm, and 500 μm data, and the IRIS 100 μm 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° and l = 59°. Methods. Applying two different methods, we determine both dust temperature and emissivity spectral index between 100 and 500 μm, at an angular resolution (θ) of 4'. Results. 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 μm, while the median dust temperatures are equal to 19.1 K and 16.0 K in the l = 30° and l = 59° field, respectively. Statistically, we do not see any significant deviations in the spectra from a power law emissivity between 100 and 500 μm. We confirm the existence of an inverse correlation between the emissivity spectral index and dust temperature, found in previous analyses.
|Additional Information:||© 2010 ESO. Received 30 June 2010; Accepted 13 September 2010. Published online 30 September 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal investigator consortia and with important participation from NASA. Data processing and maps production have been possible thanks to ASI generous support via contract I/038/080/0. M.V. is grateful to Davide Pietrobon for software support.|
|Subject Keywords:||dust, extinction; infrared: ISM|
|Official Citation:||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 and S. Molinari A&A 520 L8 (2010) DOI: 10.1051/0004-6361/201015301|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||09 Nov 2010 23:36|
|Last Modified:||26 Dec 2012 12:36|
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