J/A+A/573/A34 Magnetic field structure around cores with VeLLOs (Soam+, 2015)
Magnetic field structure around cores with very low luminosity objects.
Soam A., Maheswar G., Lee C.W., Dib S., Bhatt H.C., Tamura M.
<Astron. Astrophys. 573, A34 (2015)>
=2015A&A...573A..34S 2015A&A...573A..34S
ADC_Keywords: Molecular clouds ; Magnetic fields ; Polarization
Keywords: ISM: clouds - polarization - ISM: magnetic fields -
Abstract:
We carried out optical polarimetry of five dense cores, (IRAM 04191,
L1521F, L328, L673-7, and L1014) which are found to harbour very low
luminosity objects (VeLLOs; Lint≲0.1L☉). This study was
conducted mainly to understand the role played by the magnetic field
in the formation of very low and substellar mass range objects.
Light from the stars, while passing through the dust grains that are
aligned with their short axis parallel to an external magnetic field,
becomes linearly polarised. The polarisation position angles measured
for the stars can provide the plane-of-the sky magnetic field
orientation. Because the light in the optical wavelength range is most
efficiently polarised by the dust grains typically found at the outer
layers of the molecular clouds, optical polarimetry mostly traces the
magnetic field orientation of the core envelope.
Description:
Polarimetric observations of stars projected on five dense cores were
carried out using the Aries IMaging POLarimeter (AIMPOL) mounted at
the cassegrain focus of the 104cm Sampurnanand telescope of
Aryabhatta Research Institute of Observational Sciences (ARIES),
Nainital, India, coupled with TK 1024pix*1024pix CCD camera. Of these,
only the central 325pix*325pix are used for the observations. AIMPOL
consists of an achromatic half-wave plate (HWP) modulator and a
Wollaston prism beam-splitter. The observations of the stars
projected on three dense cores namely IRAM 04191, L673-7 and L1014
were carried out Reff=0.630um. Observations of L328 were carried out
in standard Johnson Rkc=0.760um filter. The observations of stars
towards L1521F were carried out in standard V filter of 0.550um. The
mean exposure time per observed field was ∼200s. The plate scale of
the CCD used is 1.48"/pixel and the field of view is ∼8' in diameter.
The full width at half maximum (FWHM) varies from 2 to 3 pixels. The
read out noise and gain of CCD are 7.0e- and 11.98 e-/ADU.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 69 5 List of studied sources
table4.dat 56 217 Optical polarisation results of the stars observed
in the direction of five dense cores with
Very Low Luminosity Objects
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Cloud Cloud name
12- 13 I2 h RAh Cloud right ascension (J2000)
15- 16 I2 min RAm Cloud right ascension (J2000)
18- 21 F4.1 s RAs Cloud right ascension (J2000)
23 A1 --- DE- Cloud declination sign (J2000)
24- 25 I2 deg DEd Cloud declination (J2000)
27- 28 I2 arcmin DEm Cloud declination (J2000)
30- 31 I2 arcsec DEs Cloud declination (J2000)
33- 35 I3 pc Dist [127/258] Heliocentric distance, from
Belloche et al. (2002A&A...393..927B 2002A&A...393..927B)
37- 38 I2 pc e_Dist [25/50] Mean error on Dist
40- 43 F4.2 km/s Vdisp [0.88/1.50] Velocity dispersion from
Kim et al. 2014 (in preparation)
45- 48 F4.2 km/s e_Vdisp [0.01/0.04] Mean error on Vdisp
50- 69 A20 --- SName Name of cloud in Simbad
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Cloud Cloud name
12- 14 A3 --- Filt Filter used for observations: V, Rc or Rkc
16- 17 I2 --- Seq [1/77] Star sequential number within the cluster
18 A1 --- n_Seq [a-e] Star identification or peculiarities (1)
21- 30 F10.6 deg RAdeg Right ascension (J2000)
32- 41 F10.6 deg DEdeg Declination (J2000)
43- 45 F3.1 % Pol [0.3/7.9] Degree of polarisation
47- 49 F3.1 % e_Pol [0.1/2.3] rms uncertainty on Pol
51- 53 I3 deg PA [0/180] Polarisation position angle
55- 56 I2 deg e_PA [1/14] rms uncertainty on PA
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Note (1): Notes as follows:
a = IRAS 04193+1518 (YSO)
b = [M81] I-651 (Emission-line Star)
c = K2.5 2MASS J21234472+4959478 (Emission-line Star)
d = TYC 3598-2027--1
e = K6.5 2MASS J21235851+4958086 (Emission-line Star)
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Acknowledgements:
Archana Soam, archanasoam.bhu(at)gmail.com
(End) Patricia Vannier [CDS] 24-Nov-2014