Star formation in selected Planck fields

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http://urn.fi/URN:NBN:fi:hulib-201904031591
Title: Star formation in selected Planck fields
Author: Mannfors, Emma
Contributor: University of Helsinki, Faculty of Science
Publisher: Helsingin yliopisto
Date: 2019
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-201904031591
http://hdl.handle.net/10138/300766
Thesis level: master's thesis
Discipline: Tähtitiede
Abstract: Star formation in 53 Galactic fields, selected from the Planck Catalog of Galactic Cold Clumps, has been studied using continuum submillimeter observations from the Herschel space telescope (PACS instrument 70, 100, and 160 μm, SPIRE instrument 250, 350, and 500 μm) and the James Clerk Maxwell Telescope SCUBA-2 instrument (850 μm). Fields are located at galactic latitudes between -20 and +37, and distances of 0.1-4.5 kpc. Dense clumps have been extracted from the 850-μm data using the FellWalker clumpfinding algorithm. Properties of the dust have been found by fitting a modified blackbody function to SPIRE data and clump masses have been estimated using dust properties. Whether clumps are gravitationally bound has been estimated using Bonnor-Ebert analysis. Finally, young stellar objects (YSO) from four catalogs have been associated with the clumps. Clumps are characterized as protostellar, prestellar or starless with protostellar sources having at least one YSO spatially related to them. Prestellar clumps are gravitationally bound while starless clumps are not. Virial analysis has been performed and compared to the results of Bonnor-Ebert analysis to study the role of turbulence in these regions. FellWalker analysis found 529 dense clumps, 147 of which had sufficient data for mass estimation. Mass and radius of clumps is strongly correlated with distance. Temperature also shows a slight increase in more distant fields. These effects are due to the resolution of the SCUBA-2 instrument. Of these 147 clumps, from Bonnor-Ebert analysis 91 are protostellar, 55 prestellar, and 1 starless. The starless clump is the coldest and smallest of the whole sample. Prestellar clumps have an average temperature of 13.2 ± 1.0 K, and a column density of (1.5 ± 0.8)x 10^(22) cm^(-2). Protostellar clumps are on average larger and hotter, but have lower column density than other types of clumps. Virial analysis, which includes estimates of non-thermal support, found 91 protostellar, 17 prestellar, and 39 starless clumps, showing a strong effect of turbulence. Virial prestellar clumps are the largest, coldest and densest of the sample. These clumps represent a diverse sample of Galactic star forming regions, from high-latitude nearby clumps to distant massive clouds.


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