J/A+A/655/A76 L1172/1174 R-band polarimetric results (Saha+, 2021)
Tracing the magnetic field morphology of the LDN 1172/1174 cloud complex.
Saha P., Gopinathan M., Sharma E., Won Lee C., Ghosh T., Kim S.
<Astron. Astrophys., 655, A76 (2021)>
=2021A&A...655A..76S 2021A&A...655A..76S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, standard ; Polarization
Keywords: techniques: polarimetric - stars: formation - ISM: clouds -
ISM: magnetic fields
Abstract:
Context. The LDN 1172/1174 cloud complex in the Cepheus Flare region
presents a hub-filament structure with the reflection nebula,
NGC 7023, illuminated by a Herbig Be star, HD 200775, which consists
of the hub with a ∼5pc long narrow filament attached to it. Formation
of a sparse cluster of low- and intermediate-mass stars is presently
taking place in the hub. Aims. The aim of this work is to map the
magnetic field geometry of LDN 1172/1174 to understand the role played
by the field lines in the formation of the molecular cloud. Methods.
Unpolarized background stars can be used to measure dichroically
polarized light produced by the magnetically aligned grains present in
molecular clouds. As these dust grains get aligned with their minor
axes parallel to the ambient magnetic field, the polarization
measurements can provide the plane-of-sky component of the magnetic
field. We made R-band polarization measurements of 249 stars projected
on the entire LDN 1172/1174 cloud complex to map the geometry of the
magnetic field of this region. Results. The magnetic field geometry
constructed from our R-band polarization measurements is found to be
parallel to the elongated structure inferred from the column density
distribution of the cloud produced using the Herschel images. Our
R-band polarization measurements are found to be in good agreement
with those obtained from Planck. There is evidence of a possible
distortion of the magnetic fields toward the northwestern part of the
cloud by HD 200775. The magnetic field strength is estimated as
∼30µG. The estimated star formation rate (SFR)/mass of
2.0±1.3%Myr-1 and 0.4±0.3%Myr-1 for LDN 1172/1174 and the
neighboring cloud complex, LDN 1147/1158, respectively, are found to
be consistent with the mean SFR/mass found for the clouds with
magnetic field orientations parallel and perpendicular to their
elongated structures, respectively. These results support earlier
findings that the clouds with magnetic field lines parallel to their
long axes seem to have higher SFRs compared to those with the magnetic
field orientation perpendicular to the cloud elongation.
Description:
Polarimetric observations of 42 fields (each field is a circle of 8'
in diameter) covering the cloud complex L1172/1174 were carried out
using the ARIES Imaging POLarimeter (AIMPOL).
Table A.1 lists the polarimetric measurements of the sample stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 55 249 R-band polarimetric results of 249 stars
observed toward L1172/1174
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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- 3 I3 --- Seq [1/249] Sequential numnber
5- 14 F10.6 deg GLON Galactic longitude
16- 24 F9.6 deg GLAT Galactic latitude
26- 28 F3.1 % P Degree of polarisation
30- 32 F3.1 % e_P Degree of polarisation error
34- 36 I3 deg theta Position angle, measured from the north to east
38 I1 deg e_theta Position angle error
40- 43 I4 pc Dist Distance
46- 49 I4 pc E_Dist Distance error (upper value)
52- 55 I4 pc e_Dist Distance error (lower value)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 17-Feb-2022