J/MNRAS/485/2825 Filaments hosting Planck Galactic cold clumps (Alina+, 2019)
Statistical analysis of the interplay between interstellar magnetic fields and
filaments hosting Planck Galactic cold clumps.
Alina D., Ristorcelli I., Montier L., Abdikamalov E., Juvela M.,
Ferriere K., Bernard J.-P., Micelotta E.R.
<Mon. Not. R. Astron. Soc., 485, 2825-2843 (2019)>
=2019MNRAS.485.2825A 2019MNRAS.485.2825A (SIMBAD/NED BibCode)
ADC_Keywords: Polarization ; Interstellar medium ; Extinction ; Radio sources
Keywords: polarization - methods: statistical - (ISM:) dust, extinction
Abstract:
We present a statistical study of the relative orientation in the
plane of the sky between interstellar magnetic fields and filaments
hosting cold clumps. For the first time, we consider both the density
of the environment and the density contrast between the filaments and
their environment. Moreover, we geometrically distinguish between the
clumps and the remaining portions of the filaments. We infer the
magnetic field orientations in the filaments and in their environment
from the Stokes parameters, assuming optically thin conditions. Thus,
we analyse the relative orientations between filaments, embedded
clumps, internal and background magnetic fields, depending on their
environment and evolutionary stages. We recover the previously
observed trend for filaments in low column density environments to be
aligned parallel to the background magnetic field; however, we find
that this trend is significant only for low-contrast filaments,
whereas high-contrast filaments tend to be randomly orientated with
respect to the background magnetic field. Filaments in high column
density environments do not globally show any preferential
orientation, although low-contrast filaments alone tend to have
perpendicular relative orientation with respect to the background
magnetic field. For a subsample of nearby filaments, for which volume
densities can be derived, we find a clear transition in the relative
orientation with increasing density, at nH∼103cm-3, changing
from mostly parallel to mostly perpendicular in the off-clump portions
of filaments and from even to bimodal in clumps. Our results confirm a
strong interplay between interstellar magnetic fields and filaments
during their formation and evolution.
Description:
In our analysis, we use the Planck 353GHz full mission data, which is
a part of the Planck Product 2015 release.
The Planck all-sky Galactic cold clump catalogue (Planck Collaboration
XXVIII 2016A&A...594A..28P 2016A&A...594A..28P, Cat. J/A+A/594/A28) contains 13188 sources
detected using a dedicated method (Montier et al. 2010A&A...522A..83M 2010A&A...522A..83M;
Planck Collaboration XXIII 2011A&A...536A..23P 2011A&A...536A..23P). The method consists
of a colour-based detection of the excess emission in the cold
residual maps after subtraction of the warm component traced by IRAS
100µm observations. Clumps were fitted using elliptical Gaussian
functions, and the catalogue contains the resulting semimajor and
semiminor axes and the position angles of the ellipses. With the
exception of some sources in the Large Magellanic Cloud and in the
Small Magellanic Cloud, the catalogue excludes extragalactic sources
(Planck Collaboration XXVIII 2016A&A...594A..28P 2016A&A...594A..28P, Cat. J/A+A/594/A28)
and contains nearby cores, clumps, and distant molecular clouds. This
makes the catalogue particularly useful in studies related to the
early stages of star formation.
Several methods exist to detect filamentary structures (Sousbie
2011MNRAS.414..350S 2011MNRAS.414..350S; Soler et al. 2013ApJ...774..128S 2013ApJ...774..128S; Planck
Collaboration XI 2014A&A...571A..11P 2014A&A...571A..11P). Among those, we opted for the
SupRHT method, which is an improved version of the Rolling Hough
Transform proposed by Clark, Peek & Putman (2014ApJ...789...82C 2014ApJ...789...82C).
After applying some selection criteria, we detected 137 linear
filaments.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 103 138 Characteristics of the filaments used in the study
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See also:
J/A+A/594/A28 : Planck Catalogue of Galactic cold clumps (PGCC) (Planck+, 2016)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Object number in the Planck Galactic cold
clump (PGCC) catalogue
(Cat. J/A+A/594/A28/)
7- 13 F7.3 deg GLON Galactic longitude
15- 21 F7.3 deg GLAT Galactic latitude
23- 27 F5.1 arcmin s Filament length
29- 32 F4.1 arcmin w Filament width
34- 39 F6.1 deg PAfil2 Average position angle given by the SupRHT
method using Gaussian fit
41- 44 F4.1 deg e_PAfil2 Error on PAfil2
46- 51 F6.2 10+20cm-2 NHtot Average column density over the filament
53- 58 F6.3 10+20cm-2 e_NHtot Error on NHtot
60- 65 F6.2 10+20cm-2 NHfil Average column density over the filament
excluding clumps areas
67- 72 F6.3 10+20cm-2 e_NHfil Error on NHfil
74- 79 F6.2 10+20cm-2 NHbkg Average column density over the background
region
81- 86 F6.3 10+20cm-2 e_NHbkg Error on NHbkg
88- 92 F5.1 deg psi2 ? Average magnetic field angle over the
filament using Gaussian fit
94- 98 F5.1 deg psi1 ? Average magnetic field angle over the
filament using circular statistics
100-103 F4.1 deg e_psi1 ? Error on psi1
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-Sep-2022