Planck intermediate results. XIV. Dust emission at millimetre wavelengths in the Galactic plane
Articolo
Data di Pubblicazione:
2014
Abstract:
We use Planck HFI data combined with ancillary radio data to study the
emissivity index of the interstellar dust emission in the frequency
range 100-353 GHz, or 3-0.8 mm, in the Galactic plane. We analyse the
region l = 20�-44� and |b| <= 4� where the free-free
emission can be estimated from radio recombination line data. We fit the
spectra at each sky pixel with a modified blackbody model and two
opacity spectral indices, betamm and betaFIR,
below and above 353 GHz, respectively. We find that betamm
is smaller than betaFIR, and we detect a correlation
between this low frequency power-law index and the dust optical depth at
353 GHz, tau353. The opacity spectral index
betamm increases from about 1.54 in the more diffuse
regions of the Galactic disk, |b| = 3�-4� and
tau353 ~ 5 � 10-5, to about 1.66 in the
densest regions with an optical depth of more than one order of
magnitude higher. We associate this correlation with an evolution of the
dust emissivity related to the fraction of molecular gas along the line
of sight. This translates into betamm ~ 1.54 for a medium
that is mostly atomic and betamm ~ 1.66 when the medium is
dominated by molecular gas. We find that both the two-level system model
and magnetic dipole emission by ferromagnetic particles can explain the
results. These results improve our understanding of the physics of
interstellar dust and lead towards a complete model of the dust spectrum
of the Milky Way from far-infrared to millimetre wavelengths.
emissivity index of the interstellar dust emission in the frequency
range 100-353 GHz, or 3-0.8 mm, in the Galactic plane. We analyse the
region l = 20�-44� and |b| <= 4� where the free-free
emission can be estimated from radio recombination line data. We fit the
spectra at each sky pixel with a modified blackbody model and two
opacity spectral indices, betamm and betaFIR,
below and above 353 GHz, respectively. We find that betamm
is smaller than betaFIR, and we detect a correlation
between this low frequency power-law index and the dust optical depth at
353 GHz, tau353. The opacity spectral index
betamm increases from about 1.54 in the more diffuse
regions of the Galactic disk, |b| = 3�-4� and
tau353 ~ 5 � 10-5, to about 1.66 in the
densest regions with an optical depth of more than one order of
magnitude higher. We associate this correlation with an evolution of the
dust emissivity related to the fraction of molecular gas along the line
of sight. This translates into betamm ~ 1.54 for a medium
that is mostly atomic and betamm ~ 1.66 when the medium is
dominated by molecular gas. We find that both the two-level system model
and magnetic dipole emission by ferromagnetic particles can explain the
results. These results improve our understanding of the physics of
interstellar dust and lead towards a complete model of the dust spectrum
of the Milky Way from far-infrared to millimetre wavelengths.
Tipologia CRIS:
1.1 Articolo in rivista
Keywords:
ISM: general; Galaxy: general; radiation mechanisms: general; radio continuum: ISM; submillimeter: ISM
Elenco autori:
P., Collaboration; P. A., R.; N., Aghanim; M. I., R.; M., Arnaud; M., Ashdown; F., Atrio Barandela; J., Aumont; C., Baccigalupi; A. J., Banday; R. B., Barreiro; J. G., Bartlett; E., Battaner; K., Benabed; A., Benoit L�vy; J., Bernard; M., Bersanelli; P., Bielewicz; J., Bobin; A., Bonaldi; J. R., Bond; J., Borrill; F. R., Bouchet; F., Boulanger; M., Bucher; C., Burigana; R. C., Butler; J., Cardoso; A., Catalano; A., Chamballu; H. C., Chiang; L., Chiang; P. R., Christensen; D. L., Clements; S., Colombi; L. P., L.; F., Couchot; B. P., Crill; A., Curto; F., Cuttaia; L., Danese; R. D., Davies; R. J., Davis; P. d., Bernardis; A. d., Rosa; G. d., Zotti; J., Delabrouille; C., Dickinson; J. M., Diego; H., Dole; S., Donzelli; O., Dor�; M., Douspis; X., Dupac; T. A., En�lin; H. K., Eriksen; E., Falgarone; F., Finelli; O., Forni; M., Frailis; E., Franceschi; S., Galeotta; K., Ganga; T., Ghosh; M., Giard; G., Giardino; J., Gonz�lez Nuevo; K. M., G�rski; A., Gregorio; A., Gruppuso; F. K., Hansen; D. L., Harrison; C., Hern�ndez Monteagudo; D., Herranz; S. R., Hildebrandt; E., Hivon; W. A., Holmes; A., Hornstrup; W., Hovest; A. H., Jaffe; W. C., Jones; M., Juvela; E., Keih�nen; R., Keskitalo; T. S., Kisner; R., Kneissl; J., Knoche; M., Kunz; H., Kurki Suonio; G., Lagache; A., L�hteenm�ki; J., Lamarre; A., Lasenby; R. J., Laureijs; C. R., Lawrence; R., Leonardi; F., Levrier; M., Liguori; P. B., Lilje; M., Linden V�rnle; M., L�pez Caniego; J. F., Mac�as P�rez; B., Maffei; D., Maino; N., Mandolesi; M., Maris; D. J., Marshall; P. G., Martin; E., Mart�nez Gonz�lez; S., Masi; S., Matarrese; P., Mazzotta; A., Melchiorri; L., Mendes; A., Mennella; M., Migliaccio; S., Mitra; M., Miville Desch�nes; A., Moneti; L., Montier; G., Morgante; D., Mortlock; D., Munshi; J. A., Murphy; P., Naselsky; F., Nati; P., Natoli; H. U., N�rgaard Nielsen; F., Noviello; D., Novikov; I., Novikov; C. A., Oxborrow; L., Pagano; F., Pajot; R., Paladini; D., Paoletti; F., Pasian; G., Patanchon; M., Peel; O., Perdereau; F., Perrotta; F., Piacentini; M., Piat; E., Pierpaoli; D., Pietrobon; S., Plaszczynski; E., Pointecouteau; G., Polenta; N., Ponthieu; L., Popa; G. W., Pratt; S., Prunet; J., Puget; J. P., Rachen; W. T., Reach; R., Rebolo; M., Reinecke; M., Remazeilles; C., Renault; S., Ricciardi; T., Riller; I., Ristorcelli; G., Rocha; C., Rosset; Mart�n, J. A. Rubi�o.; B., Rusholme; M., Sandri; G., Savini; D., Scott; L. D., Spencer; J., Starck; V., Stolyarov; F., Sureau; D., Sutton; A., Suur Uski; J., Sygnet; J. A., Tauber; D., Tavagnacco; Terenzi, Luca; L., Toffolatti; M., Tomasi; M., Tristram; M., Tucci; L., Valenziano; J., Valiviita; B. V., Tent; L., Verstraete; P., Vielva; F., Villa; N., Vittorio; L. A., Wade; B. D., Wandelt; D., Yvon; A., Zacchei; A., Zonca
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