1207.4706 (Planck Collaboration)
Planck Collaboration
(Abridged for arXiv) We make use of the Planck all-sky survey to derive number counts and spectral indices of extragalactic sources -- infrared and radio sources -- from the Planck Early Release Compact Source Catalogue at 100 to 857 GHz (3mm to 350micron). After the 80% completeness cut, between 122 and 452 and sources remain, with flux densities above 0.3 and 1.9Jy over about 12,800 to 16,550 deg$^2$ (31 to 40% of the sky). Using the multi-frequency coverage of the Planck High Frequency Instrument, all the sources have been classified into dust-dominated (infrared galaxies) or synchrotron-dominated (radio galaxies) spectral energy distributions (SED). We find an approximately equal number of synchrotron and dusty sources between 217 and 353 GHz; at 353GHz or higher (respectively 217 GHz or lower) frequencies, the number is dominated by dusty (synchrotron) sources, as expected. For most of the sources, the spectral indices are also derived. We provide bright counts from 353 to 857 GHz and the contributions from dusty and synchrotron sources at all HFI frequencies, in the key spectral range where these spectra are crossing, for the first time in a coherent way. The observed counts are in the Euclidean regime. The number counts are compared to previously published data (from earlier Planck results, Herschel, BLAST, SCUBA, LABOCA, SPT, and ACT) and models. We derive the multi-frequency Euclidean level -- the plateau in the normalised differential counts at high flux-density -- and compare it to WMAP, Spitzer and IRAS results. The submillimetre number counts are not well reproduced by curre evolution models of dusty galaxies, whereas the millimetre part appears reasonably well fitted by the most recent model for synchrotron-dominated sources. Finally we provide estimates of the local luminosity density of dusty galaxies, providing the first measurements at 545 and 857 GHz.
View original:
http://arxiv.org/abs/1207.4706
No comments:
Post a Comment