Planck Early Results. VII. The Early Release Compact Source Catalog

TL;DR

This paper documents the Planck ERCSC, an early, high-reliability all-sky catalog of compact sources spanning 30–857 GHz, constructed from the first Planck sky surveys with 1.6 coverages and 60% of a second pass. It details the dual detection pipelines (PwS and SExtractor), four flux-density estimators, and a Monte-Carlo QA framework that yields a cumulative reliability threshold of $\ge 0.90$, complemented by multiple secondary quality cuts. It also introduces two multifrequency catalogs—the ESZ SZ-cluster catalog and the ECC cold-core catalog—derived from dedicated MMF3 and greybody fitting procedures, validated through cross-matches with external surveys and follow-up observations. The ERCSC provides a rich resource (>15,000 sources) for immediate follow-up with facilities like Herschel, ALMA, and VLA, while transparently outlining caveats such as variability, CO contamination, and ISM cirrus effects. Overall, the work delivers a rapid, well-characterized, multi-band catalog that advances foreground studies and facilitates astrophysical investigations across Galactic and extragalactic source populations.

Abstract

(Abridged) A brief description of the methodology of construction, contents and usage of the Planck Early Release Compact Source Catalogue (ERCSC), including the Early Cold Cores (ECC) and the Early Sunyaev-Zeldovich (ESZ) cluster catalogue is provided. The catalogue is based on data that consist of mapping the entire sky once and 60% of the sky a second time by Planck, thereby comprising the first high sensitivity radio/submillimetre observations of the entire sky. A Monte-Carlo algorithm based on the injection and extraction of artificial sources into the Planck maps was implemented to select reliable sources among all extracted candidates such that the cumulative reliability of the catalogue is >=90%. The 10sigma photometric flux density limit of the catalogue at |b|>30 deg is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30 and 857 GHz. Sources which are up to a factor of ~2 fainter than this limit, and which are present in "clean" regions of the Galaxy where the sky background due to emission from the interstellar medium is low, are included in the ERCSC if they meet the high reliability criterion. The Planck ERCSC sources have known associations to stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic interstellar medium features. A significant fraction of unclassified sources are also present in the catalogs. In addition, two early release catalogs that contain 915 cold molecular cloud core candidates and 189 SZ cluster candidates that have been generated using multi-frequency algorithms are presented. The entire source list, with more than 15000 unique sources, is ripe for follow-up characterisation with Herschel, ATCA, VLA, SOFIA, ALMA and other ground-based observing facilities.

Figures (18)

• Figure 1: The variance in units of Kelvin$^{2}$ across the entire sky, with the left panel showing the variance for the LFI frequencies and the right panel showing the variance for the HFI frequencies. At any single frequency, the variance in the all-sky maps span almost a factor of 50 over the entire sky.
• Figure 2: Plots showing the results of the Monte-Carlo analysis at 30GHz with the PwS algorithm. The upper two rows shows the results when the flux density of sources is from FLUXDET while the lower two rows shows the results when the flux density of sources is from FLUX. The set of 3 plots in the top-left and bottom-left corner show the all-sky flux-density uncertainty, differential reliability and differential completeness of the Monte-Carlo sources as a function of SNR where signal may be FLUX or FLUXDET and the noise is the background RMS. The set of four plots at the top right and bottom right show (left to right, top to bottom) the fractional flux density uncertainty, $(S_\textrm{in}-S_\textrm{out})/S_\textrm{in}$ (see Sect. \ref{['sec:catalogue']}), the distribution of the absolute positional offset, differential positional offset, as well as completeness and contamination ($1-$reliability converted to a percentage) as a function of flux density for the half of the sky with the lowest sky background RMS. The range of sky background RMS converted to a point source flux density uncertainty, is shown in the inset in mJy. The primary source selections in the catalogues are based on the reliability vs output flux density/background RMS plots such that the cumulative reliability (integral of the differential reliability) is greater than 90%.
• Figure 3: As in Figure \ref{['fig:mcres']} but at 143GHz with the PwS algorithm.
• Figure 4: As in Figure \ref{['fig:mcres']} but at 857GHz with the SExtractor algorithm.
• Figure 5: The Planck ERCSC flux density limit quantified as the faintest ERCSC source at $|b|<10\degr$ (dashed black line) and at $|b|>30\degr$ (solid black line) is shown relative to other wide area surveys. Also shown are the spectra of known sources of foreground emission as red lines; these include a S$_{\nu}\sim\nu^{-0.7}$ synchrotron component, $\nu^{-0.1}$ free-free component, a Rayleigh-Jeans component and a $\nu^{2}$ emissivity blackbody of temperature 18K. The ERCSC sensitivity is worse in the Galactic Plane due to the strong contribution of ISM emission especially at submillimetre wavelengths. In the radio regime, the effect is smaller. The faintest WMAP 7 year 5$\sigma$ sources are derived from the catalogue of gold2010wright2009. Although the flux density limits of WMAP and Planck appear to be comparable at the lowest frequencies, the Planck ERCSC is more complete as discussed in Section \ref{['sec:valid']}. The GB6 sensitivity value is from greg, AT20G flux limit from mur, SCUBA-2 All Sky Survey (SASSy) limit from the Joint Astronomy Center website while the IRAS flux density limits are from the IRAS explanatory supplement beichman.