J/MNRAS/267/755 Polarimetry in the Chamaeleon I Dark Cloud (McGregor+, 1994)
Infrared polarimetry in the Chamaeleon I dark cloud.
McGregor P.J., Harrison T.E., Hough J.H., Bailey J.A.
<Mon. Not. R. Astron. Soc., 267, 755-765 (1994)>
=1994MNRAS.267..755M 1994MNRAS.267..755M
ADC_Keywords: Polarization ; Stars, pre-main sequence
Keywords: polarization - stars: formation - stars: pre-main sequence -
ISM: magnetic fields - infrared: general
Abstract:
Position angles and magnitudes of linear polarization in the H band
have been measured for 66 stars embedded in or behind the Chamaeleon I
dark cloud. These data are used to demonstrate that the magnetic field
permeating the cloud has an ordered structure over the full extent of
the dark cloud (∼4pc), with the magnetic field direction changing
smoothly from a position angle of ∼100 degrees in the vicinity of
HD 97300 in the north to ∼140 degrees in the vicinity of HD 97048 in
the south and west. The elongation of the dark cloud is consistent
with collapse preferentially along magnetic field lines. The
polarizing efficiency of the cloud decreases with increasing
line-of-sight extinction. Cloud members show a larger range in degree
of polarization and position angle, which is interpreted as due to
anisotropic scattering local to these stars. The IRAS 11054-7706C
bipolar CO outflow is unusual in that it is oriented at >60 degrees to
the cloud magnetic field direction. The Chamaeleon Infrared Nebula is
polarized at ∼30 per cent in the H band and also is oriented at ∼50
degrees to the local magnetic field. We suggest that gravitational
forces may have overwhelmed magnetic support locally to form these
relatively massive stars.
Description:
H band polarimetry is presented for 66 stars in the direction of the
Chamaeleon I dark cloud. K band polarimetry is presented for a further
two stars. The data were obtained with the Mark II Hatfield
polarimeter on the 3.9-m Anglo-Australian Telescope. Equatorial
coordinates are provided for the 68 stars. These were not presented in
the original paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 67 37 Polarimetry for probable background stars
table2.dat 70 31 Polarimetry for member stars
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Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Object identification
8- 9 I2 h RAh Right ascension (B1950.0)
11- 12 I2 min RAm Right ascension (B1950.0)
14- 17 F4.1 s RAs Right ascension (B1950.0)
19 A1 --- DE- Declination sign (B1950.0)
20- 21 I2 deg DEd Declination (B1950.0)
23- 24 I2 arcmin DEm Declination (B1950.0)
26- 27 I2 arcsec DEs Declination (B19500.0)
29- 33 F5.2 % PolH H band polarization percentage (1)
35- 38 F4.2 % e_PolH Error in H Band polarization percentage (1)
40- 44 F5.1 deg PAH H band polarization position angle (1)
46- 49 F4.1 deg e_PAH Error in H band position angle (1)
51- 52 I2 mag AV ? Estimated visual extinction (2)
54- 70 A17 --- Names Other names
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Note (1): In table1 only.
Note (2): Measurements for W4-5 and W4-6 are K-band polarizations.
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Acknowledgements:
Peter McGregor, Peter.McGregor(at)anu.edu.au
(End) Peter McGregor [ANU, Australia], Patricia Vannier [CDS] 14-Jul-2009