J/A+A/684/A132 Zero-polarization candidate regions (Mandarakas+, 2024)
Zero-polarization candidate regions for the calibration of wide-field optical
polarimeters.
Mandarakas N., Panopoulou G.V., Pelgrims V., Potter S.B., Pavlidou V.,
Ramaprakash A., Tassis K., Blinov D., Kiehlmann S., Koutsiona E.,
Maharana S., Romanopoulos S., Skalidis R., Vervelaki A., Clark S.E.,
Kypriotakis J.A., Readhead A.C.S.
<Astron. Astrophys. 684, A132 (2024)>
=2024A&A...684A.132M 2024A&A...684A.132M (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Polarization ; Infrared
Keywords: polarization - methods: observational - techniques: polarimetric -
catalogs - ISM: general
Abstract:
The calibration of optical polarimeters relies on the use of
stars with negligible polarization (i.e., unpolarized standard stars)
for determining the instrumental polarization zero point. For
wide-field polarimeters, calibration is often done by imaging the same
star over multiple positions in the field of view (FoV), which is a
time-consuming process. A more effective technique is to target fields
containing multiple standard stars. While this method has been used
for fields with highly polarized stars, there are no such sky regions
with well measured unpolarized standard stars.
We aim to identify sky regions with tens of stars exhibiting
negligible polarization that are suitable for a zero-point calibration
of wide-field polarimeters.
We selected stars in regions with extremely low reddening, located at
high Galactic latitudes. We targeted four ∼40'x40' fields in
the northern and eight in the southern equatorial hemispheres.
Observations were carried out at the Skinakas Observatory and the
South African Astronomical Observatory. Results. We found two fields
in the north and seven in the south characterized by a mean
polarization lower than p<0.1%.
At least 9 out of the 12 fields can be used for a zero-point
calibration of wide-field polarimeters.
Description:
Polarimetric measurements in sdss-r' and R bands of stars in 12
zero-polarization candidate regions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 114 304 Catalog of polarimetric measurements
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 GAIA DR3 source_id
21- 28 F8.4 deg RAdeg Right Ascension (ICRS) at Ep=2026.0
30- 37 F8.4 deg DEdeg Declination (ICRS) at Ep=2026.0
39- 46 F8.5 --- q q=Q/I Stokes parameter
48- 54 F7.5 --- e_q Uncertainty of q
56- 63 F8.5 --- u u=U/I Stokes parameter
65- 71 F7.5 --- e_u Uncertainty of u
73- 80 E8.3 --- p Polarization degree
81- 88 E8.3 --- debp Debiased estimator of p
89- 95 F7.5 --- e_p Uncertainty of p
97-102 F6.2 deg EVPA Polarization position angle North-to-East
104-109 F6.2 deg e_EVPA [] Uncertainty of EVPA
111-114 A4 --- Field zero-polarization candidate field
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Acknowledgements:
Nikos Mandarakas, nmandarakas(at)physics.uoc.gr
(End) Patricia Vannier [CDS] 08-Feb-2024