Planck intermediate results. XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck
Journal
Date Issued
2015
Author(s)
Planck Collaboration
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Fermi Collaboration
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Ade, P. A. R.
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Aghanim, N.
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Aniano, G.
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Arnaud, M.
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Ashdown, M.
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Aumont, J.
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Baccigalupi, C.
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Banday, A. J.
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Barreiro, R. B.
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Bartolo, N.
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Battaner, E.
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Benabed, K.
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Benoit-Lévy, A.
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Bernard, J. -P.
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Bersanelli, M.
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Bielewicz, P.
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Bonaldi, A.
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Bonavera, L.
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Bond, J. R.
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Borrill, J.
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Bouchet, F. R.
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Boulanger, F.
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Butler, R. C.
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Calabrese, E.
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Cardoso, J. -F.
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Casandjian, J. M.
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Catalano, A.
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Chamballu, A.
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Chiang, H. C.
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Christensen, P. R.
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Colombo, L. P. L.
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Combet, C.
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Couchot, F.
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Crill, B. P.
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Curto, A.
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Danese, L.
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Davies, R. D.
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Davis, R. J.
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de Bernardis, P.
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de Zotti, G.
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Delabrouille, J.
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Désert, F. -X.
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Dickinson, C.
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Diego, J. M.
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Digel, S. W.
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Dole, H.
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Donzelli, S.
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Doré, O.
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Douspis, M.
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Ducout, A.
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Dupac, X.
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Efstathiou, G.
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Elsner, F.
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Enßlin, T. A.
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Eriksen, H. K.
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Falgarone, E.
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Forni, O.
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Fraisse, A. A.
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Frejsel, A.
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Fukui, Y.
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Galli, S.
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Ganga, K.
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Ghosh, T.
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Giard, M.
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Gjerløw, E.
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González-Nuevo, J.
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Górski, K. M.
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Gregorio, A.
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Grenier, I. A.
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Hansen, F. K.
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Hanson, D.
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Harrison, D. L.
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Henrot-Versillé, S.
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Hernández-Monteagudo, C.
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Herranz, D.
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Hildebrandt, S. R.
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Hivon, E.
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Hobson, M.
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Holmes, W. A.
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Hovest, W.
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Huffenberger, K. M.
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Hurier, G.
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Jaffe, A. H.
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Jaffe, T. R.
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Jones, W. C.
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Juvela, M.
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Keihänen, E.
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Keskitalo, R.
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Kisner, T. S.
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Kneissl, R.
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Knoche, J.
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Kunz, M.
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Kurki-Suonio, H.
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Lagache, G.
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Lamarre, J. -M.
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Lasenby, A.
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Lattanzi, M.
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Lawrence, C. R.
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Leonardi, R.
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Levrier, F.
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Liguori, M.
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Lilje, P. B.
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Linden-Vørnle, M.
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López-Caniego, M.
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Lubin, P. M.
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Macías-Pérez, J. F.
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Maffei, B.
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Maino, D.
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Mandolesi, N.
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Marshall, D. J.
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Martin, P. G.
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Martínez-González, E.
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Masi, S.
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Matarrese, S.
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Mazzotta, P.
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Melchiorri, A.
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Mendes, L.
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Mennella, A.
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Migliaccio, M.
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Miville-Deschênes, M. -A.
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Moneti, A.
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Montier, L.
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Mortlock, D.
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Munshi, D.
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Murphy, J. A.
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Naselsky, P.
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Natoli, P.
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Nørgaard-Nielsen, H. U.
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Novikov, D.
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Novikov, I.
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Oxborrow, C. A.
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Pagano, L.
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Pajot, F.
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Paladini, R.
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Pasian, F.
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Perdereau, O.
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Perotto, L.
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Perrotta, F.
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Pettorino, V.
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Piacentini, F.
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Piat, M.
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Plaszczynski, S.
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Pointecouteau, E.
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Polenta, G.
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Popa, L.
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Pratt, G. W.
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Prunet, S.
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Puget, J. -L.
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Rachen, J. P.
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Reach, W. T.
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Rebolo, R.
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Reinecke, M.
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Remazeilles, M.
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Renault, C.
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Ristorcelli, I.
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Rocha, G.
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Roudier, G.
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Rusholme, B.
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Santos, D.
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Scott, D.
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Spencer, L. D.
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Stolyarov, V.
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Strong, A. W.
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Sudiwala, R.
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Sunyaev, R.
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Sutton, D.
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Suur-Uski, A. -S.
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Sygnet, J. -F.
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Tauber, J. A.
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Tibaldo, L.
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Toffolatti, L.
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Tomasi, M.
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Tristram, M.
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Tucci, M.
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Valiviita, J.
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Van Tent, B.
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Vielva, P.
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Wade, L. A.
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Wandelt, B. D.
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Wehus, I. K.
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Yvon, D.
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Zonca, A.
Description
The development of Planck has been supported by: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN, J.A., and RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); and PRACE (EU). A description of the Planck Collaboration and a list of its members, including the technical or scientific activities in which they have been involved, can be found at http://www.sciops.esa.int/index.php?project=planckpage=Planck_Collaboration . The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Énergie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. Support from the Institut Universitaire de France is acknowledged.
Abstract
The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, NH, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H2 conversion factor, XCO; and (iii) probe the dust properties per gas nucleon in each phase and map their spatial variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ353; the thermal radiance of the large grains; and an estimate of the dust extinction, AVQ, empirically corrected for the starlight intensity. The dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV-TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the H i-DNM-CO transitions for five separate clouds. CO-dark H2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected AVQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in AVQ/NH with increasing NH and molecular fraction, and with decreasing dust temperature. The rise in τ353/NH is even steeper. We observe variations of lesser amplitude and orderliness for the specific power of the grains, except for a coherent decline by half in the CO cores. This combined information suggests grain evolution. We provide average values for the dust properties per gas nucleon in the different phases. The γ rays and dust radiance yield consistent XCO estimates near 0.7 × 1020 cm-2 K-1 km-1 s. The AVQ and τ353 tracers yield biased values because of the large rise in grain opacity in the CO clouds. These results clarify a recurrent disparity in the γ-ray versus dust calibration of XCO, but they confirm the factor of 2 difference found between the XCO estimates in nearby clouds and in the neighbouring spiral arms.
Appendices are available in electronic form at http://www.aanda.org
Volume
582
Start page
A31
Issn Identifier
0004-6361
Ads BibCode
2015A&A...582A..31P
Rights
open.access
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