Planckearly results. XXIII. The first all-sky survey of Galactic cold clumps

Abstract

We present the statistical properties of the Cold Clump Catalogue of Planck Objects (C3PO), the first all-sky catalogue of cold objects, in terms of their spatial distribution, dust temperature, distance, mass, and morphology. We have combined Planck and IRAS data to extract 10 342 cold sources that stand out against a warmer environment. The sources are distributed over the whole sky, including in the Galactic plane, despite the confusion, and up to high latitudes (>30 • ). We find a strong spatial correlation of these sources with ancillary data tracing Galactic molecular structures and infrared dark clouds where the latter have been catalogued. These cold clumps are not isolated but clustered in groups. Dust temperature and emissivity spectral index values are derived from their spectral energy distributions using both Planck and IRAS data. The temperatures range from 7 K to 19 K, with a distribution peaking around 13 K. The data are inconsistent with a constant value of the associated spectral index β over the whole temperature range: β varies from 1.4 to 2.8, with a mean value around 2.1. Distances are obtained for approximately one third of the objects. Most of the detections lie within 2 kpc of the Sun, but more distant sources are also detected, out to 7 kpc. The mass estimates inferred from dust emission range from 0.4 M to 2.4 × 10 5 M . Their physical properties show that these cold sources trace a broad range of objects, from low-mass dense cores to giant molecular clouds, hence the "cold clump" terminology. This first statistical analysis of the C3PO reveals at least two colder populations of special interest with temperatures in the range 7 to 12 K: cores that mostly lie close to the Sun; and massive cold clumps located in the inner Galaxy. We also describe the statistics of the early cold core (ECC) sample that is a subset of the C3PO, containing only the 915 most reliable detections. The ECC is delivered as a part of the Planck Early Release Compact Source Catalogue (ERCSC).

${\rm H\,\scriptsize{I}}$, CO, ANDPLANCK/IRASDUST PROPERTIES IN THE HIGH LATITUDE CLOUD COMPLEX, MBM 53, 54, 55 AND HLCG 92 – 35. POSSIBLE EVIDENCE FOR AN OPTICALLY THICK ${\rm H\,\scriptsize{I}}$ ENVELOPE AROUND THE CO CLOUDS

“…In particular, the Planck collaboration released a whole sky distribution of dust temperature T d and dust opacity τ 353 at 5 arcmin resolution which was achieved through sensitive measurements of the dust emission above 100 GHz in the Galactic foreground. Five papers by the Planck collaboration presented comparisons between CO and dust emission (Planck Collaboration et al 2011b, 2011c, 2011d. These studies derived basic physical relationships between neutral gas and dust emission and concluded that dark gas (Grenier et al 2005) occupies 15% of the ISM, where the H i emission is assumed to be optically thin.…”

The JCMT BISTRO Survey: The Distribution of Magnetic Field Strengths toward the OMC-1 Region

“…A dispersion of polarization angles is often measured as a standard deviation of the angles assuming that an underlying magnetic field is uniform with a direction equal to the mean orientation of the polarization segments over quite a large area, or the whole area, of a molecular cloud or core (e.g., Kirk et al 2006;Curran & Chrysostomou 2007;Cortes et al 2016;Choudhury et al 2019). Other methods include a nonuniform magnetic field model to fit the overall shape of polarization segments (Girart et al 2009), a two-point correlation function to determine the field structure function (e.g., Hildebrand et al 2009;Houde et al 2009;Poidevin et al 2010;Chuss et al 2019), and a spatial filter to estimate the underlying field morphology (Pillai et al 2015). applied an "unsharp masking" method that uses a moving average of polarization angles with a 36″ × 36″ subregion of Orion A to get the large-scale mean magnetic field.…”