Planck early results. XXIV. Dust in the diffuse interstellar medium and the Galactic halo^⋆

¹ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
² Agenzia Spaziale Italiana Science Data Center, c/o ESRIN, via Galileo Galilei, Frascati, Italy
³ Astroparticule et Cosmologie, CNRS UMR7164, Université Denis Diderot Paris 7,Bâtiment Condorcet, 10 rue A. Domon et Léonie Duquet, Paris, France
⁴ Astrophysics Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK
⁵ Atacama Large Millimeter/submillimeter Array, ALMA Santiago Central Offices, Alonso de Cordova 3107, Vitacura, Casilla 763 0355, Santiago, Chile
⁶ CITA, University of Toronto,60 St. George St., Toronto, ON M5S 3H8, Canada
⁷ CNRS, IRAP,9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁸ California Institute of Technology, Pasadena, California, USA
⁹ DAMTP, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK
¹⁰ DSM/Irfu/SPP, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
¹¹ DTU Space, National Space Institute, Juliane Mariesvej 30, Copenhagen, Denmark
¹² Département de physique, de génie physique et d’optique, Université Laval, Québec, Canada
¹³ Departamento de Física, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo, Spain
¹⁴ Department of Astronomy and Astrophysics, University of Toronto, 50 Saint George Street, Toronto, Ontario, Canada
¹⁵ Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, Canada
¹⁶ Department of Physics, Gustaf Hällströmin katu 2a, University of Helsinki, Helsinki, Finland
¹⁷ Department of Physics, Princeton University, Princeton, New Jersey, USA
¹⁸ Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, Indiana, USA
¹⁹ Department of Physics, University of California, Berkeley, California, USA
²⁰ Department of Physics, University of California, One Shields Avenue, Davis, California, USA
²¹ Department of Physics, University of California, Santa Barbara, California, USA
²² Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois, USA
²³ Dipartimento di Fisica G. Galilei, Università degli Studi di Padova, Via Marzolo 8, 35131 Padova, Italy
²⁴ Dipartimento di Fisica, Università La Sapienza, P.le A. Moro 2, Roma, Italy
²⁵ Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, Milano, Italy
²⁶ Dipartimento di Fisica, Università degli Studi di Trieste, Via A.Valerio 2, Trieste, Italy
²⁷ Dipartimento di Fisica, Università di Ferrara, Via Saragat 1, 44122 Ferrara, Italy
²⁸ Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, Roma, Italy
²⁹ Discovery Center, Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
³⁰ Dpto. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
³¹ European Southern Observatory,ESO Vitacura, Alonso de Cordova 3107, Vitacura, Casilla , 19001 Santiago, Chile
³² European Space Agency, ESAC, Planck Science Office, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, Madrid, Spain
³³ European Space Agency, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
³⁴ Helsinki Institute of Physics, Gustaf Hällströmin katu 2, University of Helsinki, Helsinki, Finland
³⁵ INAF - Osservatorio Astrofisico di Catania, Via S. Sofia 78, Catania, Italy
³⁶ INAF - Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova, Italy
³⁷ INAF - Osservatorio Astronomico di Roma, Via di Frascati 33, Monte Porzio Catone, Italy
³⁸ INAF - Osservatorio Astronomico di Trieste, Via GB Tiepolo 11, Trieste, Italy
³⁹ INAF/IASF Bologna, Via Gobetti 101, Bologna, Italy
⁴⁰ INAF/IASF Milano, Via E. Bassini 15, Milano, Italy
⁴¹ INRIA, Laboratoire de Recherche en Informatique, Université Paris-Sud 11, Bâtiment 490, 91405 Orsay Cedex, France
⁴² IPAG: Institut de Planétologie et d’Astrophysique de Grenoble, Université Joseph Fourier, Grenoble 1 / CNRS-INSU, UMR 5274, 38041 Grenoble, France
⁴³ Imperial College London, Astrophysics group, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK
⁴⁴ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA
⁴⁵ Institut Néel, CNRS, Université Joseph Fourier Grenoble I, 25 rue des Martyrs, Grenoble, France
⁴⁶ Institut d’Astrophysique Spatiale, CNRS UMR8617 Université Paris-Sud 11, Bâtiment 121, Orsay, France
⁴⁷ Institut d’Astrophysique de Paris, CNRS UMR7095, Université Pierre & Marie Curie, 98bis boulevard Arago, Paris, France
⁴⁸ Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
⁴⁹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵⁰ Institute of Theoretical Astrophysics, University of Oslo, Blindern, Oslo, Norway
⁵¹ Instituto de Astrofísica de Canarias,C/Vía Láctea s/n, La Laguna, Tenerife, Spain
⁵² Instituto de Física de Cantabria (CSIC-Universidad de Cantabria),Avda. de los Castros s/n, Santander, Spain
⁵³ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California, USA
⁵⁴ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁵⁵ Kavli Institute for Cosmology Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵⁶ LERMA, CNRS, Observatoire de Paris, 61 avenue de l’Observatoire, Paris, France
⁵⁷ Laboratoire AIM, IRFU/Service d’Astrophysique - CEA/DSM - CNRS - Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁵⁸ Laboratoire Traitement et Communication de l’Information, CNRS UMR 5141 and Télécom ParisTech, 46 rue Barrault, 75634 Paris Cedex 13, France
⁵⁹ Laboratoire de Physique Subatomique et de Cosmologie, CNRS/IN2P3, Université Joseph Fourier Grenoble I, Institut National Polytechnique de Grenoble, 53 rue des Martyrs, 38026 Grenoble cedex, France
⁶⁰ Laboratoire de l’Accélérateur Linéaire, Université Paris-Sud 11, CNRS/IN2P3, Orsay, France
⁶¹ Lawrence Berkeley National Laboratory, Berkeley, California, USA
⁶² Max-Planck-Institut für Astrophysik,Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
⁶³ MilliLab, VTT Technical Research Centre of Finland, Tietotie 3, Espoo, Finland
⁶⁴ NRAO, PO Box 2, Rt 28/92, Green Bank, WV 24944-0002, USA
⁶⁵ National University of Ireland, Department of Experimental Physics, Maynooth, Co. Kildare, Ireland
⁶⁶ Niels Bohr Institute, Blegdamsvej 17, Copenhagen, Denmark
⁶⁷ Observational Cosmology, Mail Stop 367-17, California Institute of Technology, Pasadena, CA, 91125, USA
⁶⁸ Optical Science Laboratory, University College London, Gower Street, London, UK
⁶⁹ SISSA, Astrophysics Sector, Via Bonomea 265, 34136 Trieste, Italy
⁷⁰ SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
⁷¹ School of Physics and Astronomy, Cardiff University,Queens Buildings, The Parade, Cardiff CF24 3AA, UK
⁷² Space Sciences Laboratory, University of California, Berkeley, California, USA
⁷³ Spitzer Science Center, 1200 E. California Blvd., Pasadena, California, USA
⁷⁴ Stanford University, Dept of Physics, Varian Physics Bldg, 382 Via Pueblo Mall, Stanford, California, USA
⁷⁵ Université de Toulouse, ,UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
⁷⁶ Universities Space Research Association, Stratospheric Observatory for Infrared Astronomy, MS 211-3, Moffett Field, CA 94035, USA
⁷⁷ University of Granada, Departamento de Física Teórica y del Cosmos, Facultad de Ciencias, Granada, Spain
⁷⁸ University of Miami,Knight Physics Building, 1320 Campo Sano Dr., Coral Gables, Florida, USA
⁷⁹ Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa, Poland

Received: 9 January 2011
Accepted: 22 September 2011

Abstract

This paper presents the first results from a comparison of Planck dust maps at 353, 545 and 857GHz, along with IRAS data at 3000 (100 μm) and 5000GHz (60 μm), with Green Bank Telescope 21-cm observations of Hi in 14 fields covering more than 800deg² at high Galactic latitude. The main goal of this study is to estimate the far-infrared to sub-millimeter (submm) emissivity of dust in the diffuse local interstellar medium (ISM) and in the intermediate-velocity (IVC) and high-velocity clouds (HVC) of the Galactic halo. Galactic dust emission for fields with average Hi column density lower than 2 × 10²⁰ cm^-2 is well correlated with 21-cm emission because in such diffuse areas the hydrogen is predominantly in the neutral atomic phase. The residual emission in these fields, once the Hi-correlated emission is removed, is consistent with the expected statistical properties of the cosmic infrared background fluctuations. The brighter fields in our sample, with an average Hi column density greater than 2 × 10²⁰ cm^-2, show significant excess dust emission compared to the Hi column density. Regions of excess lie in organized structures that suggest the presence of hydrogen in molecular form, though they are not always correlated with CO emission. In the higher Hi column density fields the excess emission at 857 GHz is about 40% of that coming from the Hi, but over all the high latitude fields surveyed the molecular mass faction is about 10%. Dust emission from IVCs is detected with high significance by this correlation analysis. Its spectral properties are consistent with, compared to the local ISM values, significantly hotter dust (T ~ 20 K), lower submm dust opacity normalized per H-atom, and a relative abundance of very small grains to large grains about four times higher. These results are compatible with expectations for clouds that are part of the Galactic fountain in which there is dust shattering and fragmentation. Correlated dust emission in HVCs is not detected; the average of the 99.9% confidence upper limits to the emissivity is 0.15 times the local ISM value at 857 and 3000GHz, in accordance with gas phase evidence for lower metallicity and depletion in these clouds. Unexpected anti-correlated variations of the dust temperature and emission cross-section per H atom are identified in the local ISM and IVCs, a trend that continues into molecular environments. This suggests that dust growth through aggregation, seen in molecular clouds, is active much earlier in the cloud condensation and star formation processes.