J/MNRAS/403/1577 Polarization towards open cluster NGC 6823 (Medhi+, 2010)
Polarization towards the young open cluster NGC 6823.
Medhi B.J., Maheswar G., Pandey J.C., Tamura M., Sagar R.
<Mon. Not. R. Astron. Soc., 403, 1577-1591 (2010)>
=2010MNRAS.403.1577M 2010MNRAS.403.1577M
ADC_Keywords: Clusters, open ; Polarization
Keywords: polarization - dust, extinction -
open clusters and associations: individual: NGC 6823
Abstract:
We present multiwavelength linear polarimetric observations of 104
stars towards the region of young open cluster NGC 6823. The
polarization towards NGC 6823 is dominated by foreground dust grains
and we found evidence for the presence of several layers of dust
towards the line of sight. The first layer of dust is approximately
located within 200pc towards the cluster, which is much closer to the
Sun than the cluster itself (∼2.1kpc). The radial distribution of
the position angles for the member stars is found to show a systematic
change, while the polarization is found to reduce towards the outer
parts of the cluster and the average position angle of the coronal
region of the cluster is very close to the inclination of the Galactic
parallel (∼32°). The size distribution of the grains within
NGC 6823 is similar to those in the general interstellar medium. The
patchy distribution of foreground dust grains is suggested to be
mainly responsible for both differential reddening and polarization
towards NGC 6823. The majority of the observed stars do not show
evidence of intrinsic polarization in their light.
Description:
The polarimetric data for the four fields (centred at
19:43:10+23:17:55; 19:43:24=+23:12:26; 19:43:24+23:23:55 and
19:42:4+23:17:43) in NGC 6823 were acquired using the ARIES Imaging
Polarimeter (AIMPOL) mounted on the Cassegrain focus of the 104cm
Sampurnanand Telescope of ARIES, Nainital in B, V and Rc photometric
bands, on 2007 May 24, May 25, June 6 and June 7.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 72 104 Observed B, V and Rc polarization values for
different stars in NGC 6823
table4.dat 69 104 Values of Pmax, λmax, σ1 and
<ε> for the observed data in NGC 6823
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID(M) ID according to this observation,
<[MMP2010] NNN> in Simbad
5- 8 A4 --- ID(B) ID according to Barkhatova
(1957SvA.....1..822B 1957SvA.....1..822B), NGC 6823 NNNa
10- 14 F5.2 mag Vmag V magnitude
16- 19 F4.2 % Bpol Measured value of polarization in B band
21- 24 F4.2 % e_Bpol rms uncertainty on PB
26- 28 I3 deg Bpa Polarization position angle (of the E vector)
in B band
30 I1 deg e_Bpa rms uncertainty on PAB
32- 35 F4.2 % Vpol Measured value of polarization in V band
37- 40 F4.2 % e_Vpol rms uncertainty on PV
42- 44 I3 deg Vpa Polarization position angle (of the E vector)
in V band
46 I1 deg e_Vpa rms uncertainty on PAV
48- 51 F4.2 % Rpol Measured value of polarization in R band
53- 56 F4.2 % e_Rpol rms uncertainty on PR
58- 60 I3 deg Rpa Polarization position angle (of the E vector)
in R band
62 I1 deg e_Rpa rms uncertainty on PAR
64- 67 F4.2 --- MP(E) [0,1]?=- Membership probability according to
Erickson (1971A&A....10..270E 1971A&A....10..270E)
69- 72 F4.2 --- MP(D) [0,1]?=- Membership probability according to
Dias et al. (2006, Cat. J/A+A/446/949)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID(M) ID according to this observation,
<[MMP2010] NNN> in Simbad
5- 8 A4 --- ID(B) ID according to Barkhatova
(1957SvA.....1..822B 1957SvA.....1..822B), NGC 6823 NNNa
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 20 F5.2 s RAs Right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
34- 37 F4.2 % Pmax Maximum polarization
39- 42 F4.2 % e_Pmax rms uncertainty on Pmax
44- 47 F4.2 um l.max Wavelength of maximal polarisation
49- 52 F4.2 um e_l.max rms uncertainty on lammax
54- 57 F4.2 --- sig1 σ1 parameter (the unit weighting error
of the fit) (2)
59- 62 F4.2 --- Dispersion of the position angle <ε>,
normalized by the mean position angle error
64- 67 F4.2 mag E(B-V) ?=- Reddenning
69 A1 --- r_E(B-V) [GSE] Reference for E(B-V) (1)
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Note (1): Reference for E(B-V) as follows:
G = According to Guetter (1992AJ....103..197G 1992AJ....103..197G)
S = According to Stone (1988AJ.....96.1389S 1988AJ.....96.1389S)
E = According to Erickson (1971A&A....10..270E 1971A&A....10..270E)
Note (2): σ1>1.6 should be indicative of the presence of intrinsic
polarization (values ≤1.6 are compatible with the Serkowski's
interstellar polarization law).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Feb-2012