J/MNRAS/513/4899 Polarization study in NGC 2345 direction (Singh+, 2022)
Polarization, polarizing efficiency, and grain alignment towards the direction
of the cluster NGC 2345.
Singh S., Pandey J.C., Hoang T.
<Mon. Not. R. Astron. Soc. 513, 4899-4912 (2022)>
=2022MNRAS.513.4899S 2022MNRAS.513.4899S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Interstellar medium ; Optical ;
Photometry ; Polarization ; Associations, stellar ;
Positional data
Keywords: polarization - techniques: polarimetric - dust, extinction -
open clusters and associations: individual: NGC 2345
Abstract:
We have investigated the grain alignment and dust properties towards
the direction of the cluster NGC 2345 using the multiband optical
polarimetric observations. For the majority of the stars, the observed
polarization is found to be due to the interstellar medium with
average values of maximum polarization and wavelength corresponding to
it as 1.55 per cent and 0.58 µm, respectively. This reveals a
similar size distribution of dust grains to that in the general
interstellar medium in the direction of NGC 2345. Alteration of dust
properties near the distance of 1.2 kpc towards the direction of NGC
2345 has been noticed. The dust grains located beyond this distance
are found to be aligned with the Galactic magnetic field, whereas a
dispersion in the orientation of the dust grains lying in the
foreground of this distance is found. Polarizing efficiency of grains
in this direction is found to be close to the average efficiency for
our Galaxy. The decreased grain size along with the increased
polarizing efficiency towards the core region of the cluster indicates
the local radiation field is higher within the cluster, which is
responsible for the increased alignment efficiency of small grains.
The wavelength of maximum polarization (associated with the average
size of aligned grains) is also found to increase with extinction and
reduces with the increase in polarizing efficiency, which can be
explained by the radiative torque alignment mechanism.
Description:
In this paper, we present a multiband polarimetric study for an open
star cluster NGC 2345. The open cluster NGC 2345 is a young cluster in
Canis Major constellation, (i.e see section Introduction). Concerning
observations and data reduction, we use ARIES imaging polarimeter
AIMPOL for cluster NGC 2345 and a field region. The observations were
performed in four pass-bands, B (λeff = 0.44 µm), V
(λeff = 0.55 µm), R (λeff = 0.67 µm), and
I (λeff = 0.80 µm).
As there is no grid in AIMPOL, the overlapping of images can not be
avoided. Thus we have manually selected the isolated sources in each
our 4 bands. Owing to this and considering the offset of the observed
regions in different days, we have selected 172 stars in B, 146 in V,
168 in R, and 156 in I bands. Further, we have discarded those values
of a polarization for which the relative error is more than 0.5 or >
2σ. A total of 197 sources, of which 135 are of the cluster
region and 62 from the field region are included in this study. More,
we have cross-matched our stars with the Gaia DR2 data sets and
fulfilled by the condition for a good astrometric solution (Lindegren
et al. 2018A&A...616A...2L 2018A&A...616A...2L). Membership probability MP of observed
stars in the cluster NGC 2345 are taken from Cantat-Gaudin et al.
(2018A&A...618A..93C 2018A&A...618A..93C, Cat. J/A+A/618/A93) considering NGC 2345
membership only when MP > 0.5, (i.e see section 2). Then, we compute
the degree of polarization and polarization position angle in the 4
bands for observed sources as the table1.dat shows (see section 3
Results and analysis).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 137 197 The degree of polarization P and polarization
position angle (Θ) in four bands B/V/R/I
for observed stars in the cluster NGC 2345 and
a field region
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See also:
J/A+A/618/A93 : Gaia DR2 open clusters in the Milky Way (Cantat-Gaudin+, 2018)
J/AJ/161/149 : Vilnius photometry in IC 59 and IC 63 (Soam+, 2021)
J/AJ/160/256 : Polarization of 125 stars in NGC 1817 open cluster
(Singh+, 2020)
J/A+A/631/A124 : NGC 2345 Stroemgren photometry (Alonso-Santiago+, 2019)
J/A+A/558/A53 : Milky Way global survey of star clusters. II.
(Kharchenko+, 2013)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Region Region Cluster or Field region
16- 18 I3 --- ID Identifier number (ID)
20 A1 --- n_ID ID marked with asterisk symbol are members of
the cluster NGC 2345
22- 40 I19 --- GaiaDR2 Gaia DR2 source identifier (Gaia)
42- 45 F4.2 arcsec Offset Offset position between ARIES and Gaia
positions (Offset)
47- 50 F4.2 % PB ? Degree of polarization in the B band (PB)
52- 55 F4.2 % e_PB ? Mean error of PB (errorPB)
57- 61 F5.1 deg PAB ? Position angle of polarization in the B
band (ΘB)
63- 66 F4.1 deg e_PAB ? Mean error of PAB (errorΘB)
68- 71 F4.2 % PV ? Degree of polarization in the V band (PV)
73- 76 F4.2 % e_PV ? Mean error of PV (errorPV)
78- 83 F6.2 deg PAV ? Position angle of polarization in the V
band (ΘV)
85- 89 F5.2 deg e_PAV ? Mean error of PAV ( (errorΘV)
91- 96 F6.2 % PR ? Degree of polarization in the R band (PR)
98- 101 F4.2 % e_PR ? Mean error of PR (errorPR)
103- 108 F6.2 deg PAR ? Position angle of polarization in the R
band (ΘR)
110- 114 F5.2 deg e_PAR ? Mean error of PAR (errorΘR)
116- 121 F6.2 % PI ? Degree of polarization in the I band (PI)
123- 126 F4.2 % e_PI ? Mean error of PI (errorPI)
128- 132 F5.1 deg PAI ? Position angle of polarization in the I
band (ΘI)
134- 137 F4.1 deg e_PAI ? Mean error of PAI (errorΘI)
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 10-Jan-2025