Galactic cold cores
Department of Physics, PO Box 64, 00014, University of
2 Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
3 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
4 LERMA, CNRS UMR8112, Observatoire de Paris, 61 avenue de l’Observatoire, 75014 Paris, France
5 LERMA, CNRS UMR8112, Observatoire de Paris and École Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
6 The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902, Japan
7 IPAC, Caltech, Pasadena, USA
8 Laboratoire AIM Paris-Saclay, CEA/DSM – INSU/CNRS – Université Paris Diderot, IRFU/SAp CEA-Saclay, 91191 Gif-sur-Yvette, France
9 Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest, PO Box 67, Hungary
10 Loránd Eötvös University, Department of Astronomy, Pázmány P.s. 1/a, 1117 Budapest, Hungary ( OTKA K62304 )
11 IAS, Université Paris-Sud, 91405 Orsay Cedex, France
12 Laboratoire d’Astrophysique de Marseille, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13, France
13 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
Accepted: 7 February 2012
Context. In the project galactic cold cores we are carrying out Herschel photometric observations of cold regions of the interstellar clouds as previously identified with the Planck satellite. The aim of the project is to derive the physical properties of the population of cold clumps and to study its connection to ongoing and future star formation.
Aims. We examine the cloud structure around the Planck detections in 71 fields observed with the Herschel SPIRE instrument by the summer of 2011. We wish to determine the general physical characteristics of the fields and to examine the morphology of the clouds where the cold high column density clumps are found.
Methods. Using the Herschel SPIRE data, we derive colour temperature and column density maps of the fields. Together with ancillary data, we examine the infrared spectral energy distributions of the main clumps. The clouds are categorised according to their large scale morphology. With the help of recently released WISE satellite data, we look for signs of enhanced mid-infrared scattering (“coreshine”), an indication of growth of the dust grains, and have a first look at the star formation activity associated with the cold clumps.
Results. The mapped clouds have distances ranging from ~100 pc to several kiloparsecs and cover a range of sizes and masses from cores of less than 10 M⊙ to clouds with masses in excess of 10 000 M⊙. Most fields contain some filamentary structures and in about half of the cases a filament or a few filaments dominate the morphology. In one case out of ten, the clouds show a cometary shape or have sharp boundaries indicative of compression by an external force. The width of the filaments is typically ~0.2–0.3 pc. However, there is significant variation from 0.1 pc to 1 pc and the estimates are sensitive to the methods used and the very definition of a filament. Enhanced mid-infrared scattering, coreshine, was detected in four clouds with six additional tentative detections. The cloud LDN 183 is included in our sample and remains the best example of this phenomenon. About half of the fields are associated with active star formation as indicated by the presence of mid-infrared point sources. The mid-infrared sources often coincide with structures whose sub-millimetre spectra are still dominated by the cold dust.
Key words: ISM: clouds / infrared: ISM / submillimeter: ISM / dust, extinction / stars: formation / stars: protostars
Planck (http://www.esa.int/Planck) is a project of the European Space Agency – ESA – with instruments provided by two scientific consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors provided in a collaboration between ESA and a scientific consortium led and funded by Denmark.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Appendices A–E are available in electronic form at http://www.aanda.org
© ESO, 2012