J/A+A/689/A225 BRC 17, BRC 18 and lambda Ori optical polarisation (Neha+, 2024)
Optical polarimetry study of the Lambda-Orionis star-forming region.
Neha S., Soam A., Maheswar G.
<Astron. Astrophys. 689, A225 (2024)>
=2024A&A...689A.225N 2024A&A...689A.225N (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Molecular clouds ; Polarization ; Optical
Keywords: techniques: polarimetric - ISM: clouds - ISM: magnetic fields -
galaxies: star formation
Abstract:
We present an optical polarimetry study of the nearby star-forming
region Lambda-Orionis to map the plane-of-the-sky magnetic field
geometry to understand the magnetized evolution of the HII region and
the associated small molecular clouds. We made multiwavelength
polarization observations of 34 bright stars distributed across the
region. We also present the R-band polarization measurements that
focused on the small molecular clouds, bright-rimmed clouds (BRC),
BRC 17, and BRC 18, which are located at the periphery of the HII
region. The magnetic field lines exhibit a large-scale ordered
orientation consistent with the Planck submillimeter polarization
measurements. The magnetic field lines in the two BRCs are found to be
roughly in north-south directions. However, a larger dispersion is
noted in the orientation for BRC 17 compared to BRC 18. Using a
structure-function analysis, we estimate the strength of the
plane-of-the-sky component of the magnetic field as ∼28uG for BRC 17
and ∼40uG for BRC 18. The average dust grain size and the mean value
of the total-to-selective extinction ratio (RV) in the HII region are
found to be ∼0.51±0.05um and ∼2.9±0.3, respectively. The distance
of the whole HII region is estimated as ∼392±8pc by combining
astrometry information from Global Astrometric Interferometer for
Astrophysics (Gaia) early data release 3 (EDR3, Cat. I/350) for young
stellar objects associated with BRCs and confirmed members of the
central cluster Collinder 69.
Description:
We performed the optical linear polarization observations of the LOSFR
containing BRC 17 and BRC 18 using the ARIES IMaging POLarimeter
(AIMPOL) mounted at the 104 cm Sampurnanand telescope, which is
situated at the Aryabhatta Research Institute of Observational
Sciences (ARIES), Nainital, India. We used standard Johnson VRI
filters with λVeff=0.550um, λReff=0.670um, and
λIeff=0.805um for the polarimetric observations.
Objects:
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RA (2000) DE Designation(s)
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05 31 27.78 +12 05 30.9 BRC 17 = SFO 17
05 44 29.75 +09 08 53.7 BRC 18 = SFO 18
05 35 10.07 +09 48 46.7 lambda Ori cluster = Cl Collinder 69
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 106 34 Polarization results for the observed Tycho stars
in the VRI filters toward the lambda-Ori region
tablea2.dat 45 276 Polarization results of 105 stars observed in
the direction of BRC 17 and 171 stars observed
toward BRC 18 with P/σP≥2 in the R filter
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- ID [1/34] Star sequential number
4- 12 F9.6 deg RAdeg Right ascension (J2000)
14- 22 F9.6 deg DEdeg Declination (J2000)
24- 26 F3.1 % PV Polarisation degree in V band
28- 30 F3.1 % e_PV Polarisation degree in V band error
32- 34 I3 deg thetaV Polarisation position angle in V band
36- 37 I2 deg e_thetaV Polarisation position angle in V band error
39- 41 F3.1 % PR Polarisation degree in R band
43- 45 F3.1 % e_PR Polarisation degree in R band error
47- 49 I3 deg thetaR Polarisation position angle in R band
51- 52 I2 deg e_thetaR Polarisation position angle in R band error
54- 56 F3.1 % PI Polarisation degree in I band
58- 60 F3.1 % e_PI Polarisation degree in I band error
62- 64 I3 deg thetaI Polarisation position angle in I band
66- 67 I2 deg e_thetaI Polarisation position angle in I band error
69- 72 F4.2 um lambdamax Maximum wavelength (1)
74- 77 F4.2 um e_lambdamax Maximum wavelength error (1)
79- 82 F4.2 % Pmax Maximum degree of polarization (1)
84- 87 F4.2 % e_Pmax Maximum degree of polarization error (1)
89- 92 F4.2 --- RV Total-to-selective extinction
94- 97 F4.2 --- e_RV Total-to-selective extinction error
99-102 I4 pc Dist Distance from Bailer-Jones et al.
(2021AJ....161..147B 2021AJ....161..147B, Cat. I/352)
104-106 I3 pc e_Dist Distance error from Bailer-Jones et al.
(2021AJ....161..147B 2021AJ....161..147B, Cat. I/352)
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Note (1): maximum wavelength and degree of polarization estimated from a
Serkowski fitting.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Dir Direction cloud (BRC 17 or BRC 18)
8- 10 I3 --- Star [1/171] Star sequential number within the
direction cloud
12- 20 F9.6 deg RAdeg Right ascension (J2000)
22- 30 F9.6 deg DEdeg Declination (J2000)
32- 34 F3.1 % P Polarisation degree
36- 38 F3.1 % e_P Polarisation degree error
40- 42 I3 deg theta Polarisation position angle
44- 45 I2 deg e_theta Polarisation position angle error
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Feb-2025