Planck Early Results: The Galactic Cold Core Population revealed by the first all-sky survey

We present the statistical properties of the first version of the Cold Core Catalogue of Planck Objects (C3PO), in terms of their spatial distribution, temperature, distance, mass, and morphology. We also describe the statistics of the Early Cold Core Catalogue (ECC) that is a subset of the complete catalogue, and that contains only the 915 most reliable detections. ECC is delivered as a part of the Early Release Compact Source Catalogue (ERCSC). We have used the CoCoCoDeT algorithm to extract about 10 thousand cold sources. The method uses the IRAS 100μm data as a warm template that is extrapolated to the Planck bands and subtracted from the signal, leading to a detection of the cold residual emission. We have used cross-correlation with ancillary data to increase the reliability of our sample, and to derive other key properties such as distance and mass. Temperature and dust emission spectral index values are derived using the fluxes in the IRAS 100 μm band and the three highest frequency Planck bands. The range of temperatures explored by the catalogue spans from 7 K to 17 K, and peaks around 13 K. Data are not consistent with a constant value of the associated spectral index β over the all temperature range. β ranges from 1.4 to 2.8 with a mean value around 2.1, and several possible scenarios are possible, including β(T ) and the effect of multiple temperature components folded into the measurements. For one third of the objects the distances are obtained using various methods such as the extinction signature, or the association with known molecular complexes or Infra-Red Dark Clouds. Most of the detections are within 2 kpc in the Solar neighbourhood, but a few are at distances greater than 4 kpc. The cores are distributed over the whole range of longitude and latitude, from the deep Galactic plane, despite the confusion, to high latitudes (> 30◦). The associated mass estimates derived from dust emission range from 1 to 105 solar masses. Using their physical properties such as temperature, mass, luminosity, density and size, these cold sources are shown to be cold clumps, defined as the intermediate cold sub- structures between clouds and cores. These cold clumps are not isolated but mostly organized in filaments associated with molecular clouds. The Cold Core Catalogue of Planck Objects (C3PO) is the first unbiased all-sky catalogue of cold compact objects and contains 10783 objects. It gives an unprecedented statistical view to the properties of these potential pre-stellar clumps and offers a unique possibility for their classification in terms of their intrinsic properties and environment.