Herscheland SCUBA-2 observations of dust emission in a sample ofPlanckcold clumps

Abstract

Context. Analysis of all-sky Planck submillimetre observations and the IRAS 100 µm data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Aims. Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. Methods. We examine the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compare with JCMT/SCUBA-2 850 µm maps with Herschel data that are filtered using the SCUBA-2 pipeline. Clumps are extracted using the Fellwalker method and their spectra are modelled as modified blackbody functions. Results. According to IRAS and Planck data, most fields have dust colour temperatures T C ∼ 14 − 18 K and opacity spectral index values of β = 1.5 − 1.9. The clumps/cores identified in SCUBA-2 maps have T ∼ 13 K and similar β values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 µm. In fits involving Planck data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median β value slightly above 1.8. In the joint SPIRE and SCUBA-2 850 µm fits the value decreases to β ∼1.6. Most of the observed T -β anticorrelation can be explained by noise. Conclusions. The typical submillimetre opacity spectral index β of cold clumps is found to be ∼1.7. This is above the values of diffuse clouds but lower than in some previous studies of dense clumps. There is only tentative evidence of T -β anticorrelation and β decreasing at millimetre wavelengths.

Statistical analysis of the interplay between interstellar magnetic fields and filaments hostingPlanckGalactic cold clumps

“…The Planck clumps, being elongated and more extended than the Planck beam, could be considered as a "cold matrix" linking dense substructures to each other over a broad range of scales. More recently, the SCOPE JCMT legacy survey performed with the SCUBA-2 instrument at JCMT to map about 1000 PGCCs in 850 µm continuum emission, has detected thousands of dense cores, identified as either starless cores or protostellar cores with young (Class 0/I) sources (Liu et al 2016;Tatematsu et al 2017;Juvela et al 2018a).…”

Dust spectrum and polarisation at 850 μm in the massive IRDC G035.39-00.33

“…XIV (2014). More recently, Juvela et al (2018) analysed Herschel and SCUBA-2 observations of cores and clumps within some 90 PGCC fields. For those objects the median value at Herschel wavelengths was β ∼ 1.8 (although with significant scatter) and the inclusion of the SCUBA-2 850 µm data point decreased the value closer to β ∼ 1.6.…”

The evolutionary status of protostellar clumps hosting class II methanol masers

“…A value of 1.8 is chosen as this was found to best characterise the shape of the observed SED of the clumps, consistent with previous work (e.g. Juvela et al 2015Juvela et al , 2018Guzmán et al 2015). A greybody is fitted to each constructed SED by least-squares minimisation using the Levenberg-Marquardt algorithm to return best fit values of T and M d 2 .…”