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    Planck early results. XXI. Properties of the interstellar medium in the Galactic plane

    Abergel, A. and Ade, P.A.R. and Aghanim, N. and Arnaud, M. and Ashdown, M. and Aumont, J. and Baccigalupi, C. and Balbi, A. and Banday, A.J. and Barreiro, R.B. and Bartlett, J.G. and Battaner, E. and Benabed, K. and Benoit, A. and Bernard, J.-P. and Bersanelli, M. and Bhatia, R. and Bock, J.J. and Bonaldi, A. and Bond, J.R. and Borrill, J. and Bouchet, F.R. and Boulanger, F. and Bucher, M. and Burigana, C. and Cabella, P. and Cardoso, J.-F. and Catalano, A. and Cayon, L. and Challinor, A. and Chamballu, A. and Chiang, L.-Y. and Chiang, C. and Christensen, P.R. and Colombi, S. and Couchot, F. and Coulais, A. and Crill, B.P. and Cuttaia, F. and Dame, T.M. and Danese, L. and Davies, R.D. and Davis, R.J. and De Bernardis, P. and de Gasperis, G. and de Rosa, A. and de Zotti, G. and Delabrouille, J. and Delouis, J.-M. and Desert, F.-X. and Dickinson, C. and Donzelli, S. and Dore, O. and Dorl, U. and Douspis, M. and Dupac, X. and Efstathiou, G. and Enßlin, T.A. and Finelli, F. and Forni, O. and Frailis, M. and Franceschi, E. and Galeotta, S. and Ganga, K. and Giard, M. and Giardino, G. and Giraud-Héraud, Y. and Gonzalez-Nuevo, J. and Gorski, K.M. and Gratton, S. and Gregorio, A. and Grenier, I.A. and Grupposo, A. and Hansen, F.K. and Harrison, D. and Henrot-Versille, S. and Herranz, D. and Hilderbrandt, S.R. and Hivon, E. and Hobson, M. and Holmes, W.A. and Hovest, W. and Hoyland, R.J. and Huffenberger, K.M. and Jaffe, A.H. and Jaffe, T.R. and Jones, W.C. and Juvela, M. and Keihanen, E. and Keskitalo, R. and Kisner, T.S. and Kneissl, R. and Knox, L. and Kurki-Suonio, H. and Lagache, G. and Lahteenmaki, A. and Lamarre, J.-M. and Lasenby, A. and Laureijs, R.J. and Lawrence, C.R. and Leach, S. and Leonardi, R. and Leroy, C. and Lilje, P.B. and Linden-Vornle, M. and Lopez-Caniego, M. and Lubin, P.M. and Macias-Perez, J.F. and MacTavish, C.J. and Maffei, B. and Mandolesi, N. and Mann, R. and Maris, M. and Marshall, D.J. and Martinez-Gonzalez, E. and Masi, S. and Matarrese, S. and Matthai, F. and Mazzotta, P. and McGehee, P. and Meinhold, P.R. and Melchiorri, A. and Mendes, L. and Mennella, A. and Miville-Deschenes, M.-A. and Moneti, A. and Montier, L. and Morgante, G. and Mortlock, D. and Munshi, D. and Murphy, J.Anthony and Naselsky, P. and Natoli, P. and Netterfield, C.B. and Norgaard-Nielsen, H.U. and Noviello, F. and Novikov, D. and Novikov, I. and Osborne, S. and Pajot, F. and Paladini, R. and Pasian, F. and Patanchon, G. and Perdereau, O. and Perotto, L. and Perotta, L. and Piacentini, F. and Piat, M. and Plaszczynski, S. and Pointecouteau, E. and Polenta, G. and Ponthieu, N. and Poutanen, T. and Prezeau, G. and Prunet, S. and Puget, J.-L. and Rachen, J.P. and Reach, W.T. and Rebolo, R. and Reich, W. and Renault, C. and Ricciardi, S. and Riller, T. and Ristorcelli, I. and Rocha, G. and Rosset, C. and Rubino-Martin, J.A. and Rusholme, B. and Sandri, M. and Santos, D. and Savini, G. and Scott, D. and Seiffert, M.D. and Shellard, P. and Smoot, G.F. and Starck, J.-L. and Stivoli, F. and Stolyarov, V. and Stompor, R. and Sudiwala, R. and Sygnet, J.-F. and Tauber, J.A. and Terenzi, L. and Toffolatti, L. and Tomasi, M. and Torre, J.-P. and Tristram, M. and Tuovinen, J. and Umana, G. and Valenziano, L. and Varis, J. and Vielva, P. and Villa, F. and Vittorio, N. and Wade, L.A. and Wandelt, B.D. and Wilkinson, A. and Ysard, N. and Yvon, D. and Zacchei, A. and Zonca, A. (2011) Planck early results. XXI. Properties of the interstellar medium in the Galactic plane. Astronomy & Astrophysics, 536 (A21). pp. 1-18. ISSN 0004-6361

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    Planck has observed the entire sky from 30 GHz to 857 GHz. The observed foreground emission contains contributions from different phases of the interstellar medium (ISM). We have separated the observed Galactic emission into the different gaseous components (atomic, molecular and ionised) in each of a number of Galactocentric rings. This technique provides the necessary information to study dust properties (emissivity, temperature, etc.), as well as other emission mechanisms as a function of Galactic radius. Templates are created for various Galactocentric radii using velocity information from atomic (neutral hydrogen) and molecular (12CO) observations. The ionised template is assumed to be traced by free-free emission as observed by WMAP, while 408 MHz emission is used to trace the synchrotron component. Gas emission not traced by the above templates, namely “dark gas”, as evidenced using Planck data, is included as an additional template, the first time such a component has been used in this way. These templates are then correlated with each of the Planck frequency bands, as well as with higher frequency data from IRAS and DIRBE along with radio data at 1.4 GHz. The emission per column density of the gas templates allows us to create distinct spectral energy distributions (SEDs) per Galactocentric ring and in each of the gaseous tracers from 1.4 GHz to 25 THz (12 μm). The resulting SEDs allow us to explore the contribution of various emission mechanisms to the Planck signal. Apart from the thermal dust and free-free emission, we have probed the Galaxy for anomalous (e.g., spinning) dust as well as synchrotron emission. We find the dust opacity in the solar neighbourhood, τ/NH = 0.92±0.05×10−25 cm2 at 250 μm, with no significant variation with Galactic radius, even though the dust temperature is seen to vary from over 25 K to under 14 K. Furthermore, we show that anomalous dust emission is present in the atomic, molecular and dark gas phases throughout the Galactic disk. Anomalous emission is not clearly detected in the ionised phase, as free-free emission is seen to dominate. The derived dust propeties associated with the dark gas phase are derived but do not allow us to reveal the nature of this phase. For all environments, the anomalous emission is consistent with rotation from polycyclic aromatic hydrocarbons (PAHs) and, according to our simple model, accounts for (25 ± 5)% (statistical) of the total emission at 30 GHz.

    Item Type: Article
    Keywords: ISM: general; Galaxy; general – radio continuum; ISM – submillimeter; ISM – infrared; ISM – radiation mechanisms;
    Academic Unit: Faculty of Science and Engineering > Experimental Physics
    Item ID: 4317
    Depositing User: Dr. Anthony Murphy
    Date Deposited: 15 Apr 2013 14:21
    Journal or Publication Title: Astronomy & Astrophysics
    Publisher: EDP Sciences
    Refereed: Yes

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