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Dust spectrum and polarisation at 850 μm in the massive IRDC G035.39-00.33
- Source :
- Astronomy & Astrophysics, Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2018, 620, pp.A26. ⟨10.1051/0004-6361/201833245⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2018, 620, pp.A26. ⟨10.1051/0004-6361/201833245⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2018, 620, pp.A26
- Publication Year :
- 2018
- Publisher :
- EDP Sciences, 2018.
-
Abstract
- The dust sub-millimetre polarisation of star-forming clouds carries information on dust and the role of magnetic fields in cloud evolution. With observations of a dense filamentary cloud G035.39-00.33, we aim to characterise the dust emission properties and the variations of the polarisation fraction. JCMT SCUBA-2/POL-2 data at 850um are combined with Planck 850um (353GHz) data to map polarisation fractions. With previous SCUBA-2 observations (450um and 850um) and Herschel data, the column densities are determined via modified blackbody fits and via radiative transfer modelling. Models are constructed to examine how the polarisation angles and fractions depend on potential magnetic field geometries and grain alignment. POL-2 data show clear changes in the magnetic field orientation. The filament has a peak column density of N(H2)~7 10^22 cm-2, a minimum dust temperature of T~12 K, and a mass of some 4300Msun for the area N(H2)> 5 10^21 cm-2. The estimated average value of the dust opacity spectral index is beta ~ 1.9. The ratio of sub-millimetre and J band optical depths is tau(250 um)/tau(J) ~ 2.5 10^-3, more than four times the typical values for diffuse medium. The polarisation fraction decreases as a function of column density to p ~ 1% in the central filament. Because of noise, the observed decrease of p(N) is significant only at N(H2)>2 10^22 cm-2. The observations suggest that the grain alignment is not constant. Although the data can be explained with a complete loss of alignment at densities above ~ 10^4 cm-3 or using the predictions of radiative torques alignment, the uncertainty of the field geometry and the spatial filtering of the SCUBA-2 data prevent strong conclusions. G035.39-00.33 shows strong signs of dust evolution and the low polarisation fraction is suggestive of a loss of polarised emission from its densest parts.<br />accepted for publication in Astronomy and Astrophysics
- Subjects :
- GRAIN ALIGNMENT
Opacity
RADIATIVE TORQUES
SCUBA-2 OBSERVATIONS
INFRARED OBSERVATIONS
Extinction (astronomy)
FOS: Physical sciences
Context (language use)
Astrophysics
MOLECULAR CLOUD
POLARIMETRY
ISM: clouds
01 natural sciences
Molecular physics
Protein filament
DARK CLOUD
0103 physical sciences
Radiative transfer
TAURUS
GOULD BELT SURVEY
010303 astronomy & astrophysics
QC
ComputingMilieux_MISCELLANEOUS
QB
infrared: ISM
Physics
Spectral index
stars: formation
stars: protostars
extinction
010308 nuclear & particles physics
Molecular cloud
MAGNETIC-FIELD
Astronomy and Astrophysics
115 Astronomy, Space science
Astrophysics - Astrophysics of Galaxies
Magnetic field
13. Climate action
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
submillimeter: ISM
dust, extinction
dust
[SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Subjects
Details
- ISSN :
- 14320746 and 00046361
- Volume :
- 620
- Database :
- OpenAIRE
- Journal :
- Astronomy & Astrophysics
- Accession number :
- edsair.doi.dedup.....80f6c1a4b0c28372a776e229e50db1f4