J/A+A/624/L8 Starlight polarization (Panopoulou+, 2019)
Extreme starlight polarization in a region with highly polarized dust emission.
Panopoulou G.V., Hensley B.S., Skalidis R., Blinov D., Tassis K.
<Astron. Astrophys. 624, L8 (2019)>
=2019A&A...624L...8P 2019A&A...624L...8P (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Polarization
Keywords: polarization - ISM: magnetic fields - extinction -
submillimeter: ISM - local interstellar matter
Abstract:
Galactic dust emission is polarized at unexpectedly high levels, as
revealed by Planck. The origin of the observed 20% polarization
fractions can be identified by characterizing the properties of
optical starlight polarization in a region with maximally polarized
dust emission. We measure the R-band linear polarization of 22 stars
in a region with a submillimeter polarization fraction of 20%. A
subset of 6 stars is also measured in the B, V, and I bands to
investigate the wavelength dependence of polarization. We find that
starlight is polarized at correspondingly high levels. Through
multiband polarimetry we find that the high polarization fractions are
unlikely to arise from unusual dust properties, such as enhanced grain
alignment. Instead, a favorable magnetic field geometry is the most
likely explanation, and is supported by observational probes of the
magnetic field morphology. The observed starlight polarization exceeds
the classical upper limit of [pV/E(B-V]{max}=9%/mag and is at
least as high as 13%/mag, as inferred from a joint analysis of Planck
data, starlight polarization and reddening measurements. Thus, we
confirm that the intrinsic polarizing ability of dust grains at
optical wavelengths has long been underestimated.
Description:
The catalog contains the R-band data presented in the publication,
cross- matched with the Gaia-derived catalog of stellar distances from
Bailer Jones et al. 2018AJ....156...58B 2018AJ....156...58B, Cat. I/347 (BJ2018). The data
were obtained in 2018 with the RoboPol polarimeter (Ramaprakash et
al., 2019MNRAS.485.2355R 2019MNRAS.485.2355R), mounted on the 1.3m telescope at the
Skinakas observatory in Crete, Greece.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 133 22 R-band linear polarization of stars in a region
of highly polarized dust emission
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See also:
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Star identifier from BJ2018 (Cat. I/347)
21- 32 A12 --- USNOB Star identifier from USNO-B1 (Cat. I/284)
34- 40 F7.5 deg RAdeg Gaia DR2 right ascension (ICRS at epoch 2015.5)
42- 49 F8.5 deg DEdeg Gaia DR2 declination (ICRS at epoch 2015.5)
51- 58 F8.5 --- Q Stokes q
60- 66 F7.5 --- e_Q 1-sigma error on Stokes Q
68- 75 F8.5 --- U Stokes u
77- 83 F7.5 --- e_U 1-sigma error on Stokes U
85- 91 F7.5 --- P Fractional linear polarization (1)
93- 99 F7.5 --- e_P 1-sigma error on P (1)
101-107 F7.5 --- dP Debiased fractional linear polarization (1)
109-113 F5.1 deg theta Polarization angle in the celestial frame
115-118 F4.1 deg e_theta 1-sigma error in theta
120-123 I4 pc Dist Max likelihood distance from BJ2018 (Cat. I/347)
125-128 I4 pc e_Dist Lower limit on distance
130-133 I4 pc E_Dist Upper limit on distance
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Note (1): Note that P, e_P, dP are fractions (non-dimensional).
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Acknowledgements:
Georgia Panopoulou, panopg(at)caltech.edu
(End) Patricia Vannier [CDS] 27-Mar-2019