J/ApJ/849/157 Polarimetry obs. toward IC5146 background stars (Wang+, 2017)
Multiwavelength stellar polarimetry of the filamentary cloud IC5146.
I. Dust properties.
Wang J.-W., Lai S.-P., Eswaraiah C., Clemens D.P., Chen W.-P., Pandey A.K.
<Astrophys. J., 849, 157 (2017)>
=2017ApJ...849..157W 2017ApJ...849..157W
ADC_Keywords: Polarization; Optical; Photometry, infrared; Extinction;
Star Forming Region; Interstellar medium
Keywords: dust, extinction ; ISM: clouds ; ISM: individual objects (IC5146) ;
ISM: magnetic fields ; ISM: structure ; polarization
Abstract:
We present optical and near-infrared stellar polarization observations
toward the dark filamentary clouds associated with IC5146. The data
allow us to investigate the dust properties (this paper) and the
magnetic field structure (Paper II). A total of 2022 background stars
were detected in the Rc, i', H, and/or K bands to AV≲25mag. The
ratio of the polarization percentage at different wavelengths provides
an estimate of λmax, the wavelength of the peak polarization,
which is an indicator of the small-size cutoff of the grain size
distribution. The grain size distribution seems to significantly
change at AV∼3mag, where both the average and dispersion of
PRc/PH decrease. In addition, we found λmax∼0.6-0.9µm
for AV>2.5mag, which is larger than the ∼0.55µm in the general
interstellar medium (ISM), suggesting that grain growth has already
started in low-AV regions. Our data also reveal that polarization
efficiency (PE=Pλ/AV) decreases with AV as a power law in
the Rc, i', and K bands with indices of -0.71±0.10, -1.23±0.10,
and -0.53±0.09. However, H-band data show a power index change; the
PE varies with AV steeply (index of -0.95±0.30) when
AV<2.88±0.67mag, but softly (index of -0.25±0.06) for greater AV
values. The soft decay of PE in high-AV regions is consistent with the
radiative alignment torque model, suggesting that our data trace the
magnetic field to AV∼20mag. Furthermore, the breakpoint found in the
H band is similar to that for AV, where we found the PRc/PH
dispersion significantly decreased. Therefore, the flat PE-AV in
high-AV regions implies that the power-index changes result from
additional grain growth.
Description:
We measured the polarization of background stars toward the IC5146
filamentary cloud system with several instruments: the Aryabhatta
Research Institute of Observational Sciences (ARIES) Imaging
Polarimeter (AIMPOL) and Triple-Range (g', r', i') Imager and
POLarimeter (TRIPOL; at the Lulin Observatory) provided optical Rc-
and i'-band polarimetry data, respectively. Mimir (at the Lowell
Observatory Perkins Telescope) measured the H- and K-band
polarizations at near-infrared wavelengths.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 380 48741 Measured polarization properties of stars probing
the IC5146 dark cloud complex
--------------------------------------------------------------------------------
See also:
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
VI/139 : Herschel Observation Log (Herschel Science Centre, 2013)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
J/ApJ/665/369 : Photopolarimetry of Southern Coalsack stars (Andersson+, 2007)
J/A+A/502/845 : Dust coagulation in molecular clouds (Ormel+, 2009)
J/ApJ/741/21 : Polarization of stars in Taurus (Chapman+, 2011)
J/A+A/569/L1 : Polarization hole in a starless core (Alves+, 2014)
J/ApJ/793/126 : L204 - Cloud 3 polarimetry and photometry (Cashman+, 2014)
J/ApJ/833/176 : The magnetic field of L1544. I. NIR data (Clemens+, 2016)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 -- Seq [1/48741] Polarimetric Catalog Star Number
7- 15 F9.5 deg RAdeg [325.7/328.9] Right Ascension (J2000)
17- 24 F8.5 deg DEdeg [46.5/48.5] Declination (J2000)
26- 32 F7.2 % QR [-2.6/4]?=-999 Normalized Stokes Q in Rc-band
34- 40 F7.2 % e_QR [0.02/0.8]?=-999 Uncertainty in QR
42- 48 F7.2 % UR [-3.3/6.3]?=-999 Normalized Stokes U in Rc-band
50- 56 F7.2 % e_UR [0.01/0.8]?=-999 Uncertainty in UR
58- 64 F7.2 % PR [0/6.4]?=-999 Debiased Rc-band polarization
percentage
66- 72 F7.2 % e_PR [0.03/0.8]?=-999 Uncertainty in PR
74- 80 F7.2 deg PAR [0.6/180]?=-999 Rc-band Polarization Angle
82- 88 F7.2 deg e_PAR [0.3/75]?=-999 Uncertainty in PAR
90- 96 F7.2 % Qi [-3.7/6]?=-999 Normalized Stokes Q in i'-band
98-104 F7.2 % e_Qi [0.02/1]?=-999 Uncertainty in Qi
106-112 F7.2 % Ui [-2.4/6.6]?=-999 Normalized Stokes U in i'-band
114-120 F7.2 % e_Ui [0.02/1]?=-999 Uncertainty in Ui
122-128 F7.2 % Pi [0.5/6.6]?=-999 Debiased i'-band polarization
percentage
130-136 F7.2 % e_Pi [0.02/1]?=-999 Uncertainty in Pi
138-144 F7.2 deg PAi [0.5/180]?=-999 i'-band Polarization Angle
146-152 F7.2 deg e_PAi [0.3/9.5]?=-999 Uncertainty in PAi
154-160 F7.2 % QH [-99.9/99.9]?=-999 Normalized Stokes Q in H-band
162-168 F7.2 % e_QH [0.08/99.9]?=-999 Uncertainty in QH
170-176 F7.2 % UH [-99.9/99.9]?=-999 Normalized Stokes U in H-band
178-184 F7.2 % e_UH [0.08/99.9]?=-999 Uncertainty in UH
186-192 F7.2 % PH [0/99.9]?=-999 Debiased H-band polarization
percentage
194-200 F7.2 % e_PH [0.08/99]?=-999 Uncertainty in PH
202-208 F7.2 deg PAH [0/180]?=-999 H-band Polarization Angle
210-216 F7.2 deg e_PAH [1.3/180]?=-999 Uncertainty in PAH
218-224 F7.2 % QK [-95.3/99.9]?=-999 Normalized Stokes Q in K-band
226-232 F7.2 % e_QK [0.1/99.9]?=-999 Uncertainty in QK
234-240 F7.2 % UK [-99.1/89.5]?=-999 Normalized Stokes U in K-band
242-248 F7.2 % e_UK [0.1/99.9]?=-999 Uncertainty in UK
250-256 F7.2 % PK [0/99.9]?=-999 Debiased K-band polarization
percentage
258-264 F7.2 % e_PK [0.1/99]?=-999 Uncertainty in PK
266-272 F7.2 deg PAK [0/180]?=-999 K-band Polarization Angle
274-280 F7.2 deg e_PAK [2.8/180]?=-999 Uncertainty in PAK
282-289 F8.3 mag Jmag [5.5/17.6]?=-999 2MASS J-band magnitude
291-298 F8.3 mag e_Jmag [0.007/2.3]?=-999 Uncertainty in Jmag
300-307 F8.3 mag Hmag [4.4/16.5]?=-999 2MASS H-band magnitude
309-316 F8.3 mag e_Hmag [0.007/1]?=-999 Uncertainty in Hmag
318-325 F8.3 mag Ksmag [3.9/16.3]?=-999 2MASS Ks-band magnitude
327-334 F8.3 mag e_Ksmag [0.005/0.8]?=-999 Uncertainty in Kmag
336-343 F8.3 mag W1mag [4/16.1]?=-999 WISE band 1 magnitude
345-352 F8.3 mag e_W1mag [0.02/0.5]?=-999 Uncertainty in W1mag
354-361 F8.3 mag W2mag [4/17.7]?=-999 WISE band 2 magnitude
363-370 F8.3 mag e_W2mag [0.01/0.6]?=-999 Uncertainty in W2mag
372-378 F7.2 mag Av [-3.7/28.8]?=-999 NICER extinction (1)
380-380 I1 -- UF [0/1] Usage Flag: 1=Selected for further
analysis; 0=Not selected
--------------------------------------------------------------------------------
Note (1): The uncertainties of Av are 0.93mag, estimated in Section 3.1.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Jun-2018