J/ApJ/741/112 IR polarization data in the BN region (Poidevin+, 2011)
Multi-scale analysis of magnetic fields in filamentary molecular clouds
in Orion A.
Poidevin F., Bastien P., Jones T.J.
<Astrophys. J., 741, 112 (2011)>
=2011ApJ...741..112P 2011ApJ...741..112P (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Polarization ; Infrared sources ;
Magnetic fields
Keywords: ISM: individual (Orion A, OMC-1, OMC-2, OMC-3, OMC-4) -
ISM: magnetic fields - polarization
Abstract:
New visible and K-band polarization measurements of stars surrounding
molecular clouds in Orion A and stars in the Becklin-Neugebauer (BN)
vicinity are presented. Our results confirm that magnetic fields
located inside the Orion A molecular clouds and in their close
neighborhood are spatially connected. On and around the BN object, we
measured the angular offsets between the K-band polarization data and
available submillimeter (submm) data. We find high values of the
polarization degree, PK, and of the optical depth, τK, close
to an angular offset position of 90° whereas lower values of PK
and τK are observed for smaller angular offsets. We interpret
these results as evidence for the presence of various magnetic field
components toward lines of sight in the vicinity of BN. On a larger
scale, we measured the distribution of angular offsets between
available H-band polarization data and the same submm data set. Here
we find an increase of <PH> with angular offset, which we interpret
as a rotation of the magnetic field by ≲60°. This trend
generalizes previous results on small scales toward and around lines
of sight to BN and is consistent with a twist of the magnetic field on
a larger scale toward OMC-1. A comparison of our results with several
other studies suggests that a two-component magnetic field, perhaps
helical, could be wrapping the OMC-1 filament.
Description:
Polarimetry on and around the BN object was done on 33 stars on 2002
February 15 (UT) using NSFCAM on the IRTF in polarimetry mode. The
filter was the standard IRTF K-band filter centered on λ=2.2µm.
A description of NSFCAM in polarimetry mode was given by Jones
(1997AJ....114.1393J 1997AJ....114.1393J).
Objects:
----------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------
05 35 17.3 -05 23 28 Orion A = M 42
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 71 33 IR Polarization Data in the BN Region
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See also:
J/ApJ/604/717 : Polarization in OMC 1/4 (Houde+, 2004)
J/AJ/136/621 : Near-infrared polarimetry of M42 (Kusakabe+, 2008)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Star [0/38] Star number (NN)
4- 5 A2 --- n_Star [BN ] Note on star (1)
7 I1 h RAh Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 15 F4.1 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18 A1 deg DEd Degree of Declination (J2000)
20- 21 I2 arcmin DEm Arcminute of Declination (J2000)
23- 26 F4.1 arcsec DEs Arcsecond of Declination (J2000)
28- 31 F4.1 % PK Degree of polarization in K band (2)
33- 37 F5.1 deg thetaK Position angle in K band
39- 42 F4.1 deg e_thetaK Uncertainty in thetaK
44- 47 F4.2 mag H-K H-K color index
49- 50 A2 --- LBLS Possible source identification in
Lonsdale et al. (1982AJ.....87.1819L 1982AJ.....87.1819L),
LBLS a in Simbad
52- 54 A3 --- S+S Possible source identification in
Stolovy et al. (1998ApJ...492L.151S 1998ApJ...492L.151S),
[SBE98] CBN in Simbad and
Shuping et al. (2004AJ....128..363S 2004AJ....128..363S),
[RLK73] IRc NNW in Simbad
56- 60 A5 --- ID Other identification designation
62- 63 I2 deg thetaoff [2/82]? Angular offset between 2.2 µm
and 350 µm
65- 69 F5.2 --- tauK Optical depth
71 A1 --- SC [0/1] Selection code (3)
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Note (1): Note as follows:
BN = Becklin-Neugebauer region.
Note (2): A precision of σP=±0.3% can be assumed for these data.
Note (3): Indicates the reliability of polarization data to probe magnetic
fields. Code as follows:
1 = For reliable data;
0 = Otherwise.
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 18-Aug-2017