Zero-polarization candidate regions for the calibration of wide-field optical polarimeters
Journal article, 2024
Context. 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. Aims. 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. Methods. We selected stars in regions with extremely low reddening, located at high Galactic latitudes. We targeted four ∼40′ × 40′ 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%. Conclusions. At least 9 out of the 12 fields can be used for a zero-point calibration of wide-field polarimeters.
polarization
ISM: general
methods: observational
catalogs
techniques: polarimetric
Author
N. Mandarakas
University of Crete
Foundation for Research and Technology-Hellas (FORTH)
Georgia Virginia Panopoulou
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
V. Pelgrims
Université libre de Bruxelles (ULB)
S. B. Potter
South African Astronomical Observatory
University of Johannesburg
V. Pavlidou
University of Crete
Foundation for Research and Technology-Hellas (FORTH)
A. N. Ramaprakash
California Institute of Technology (Caltech)
Foundation for Research and Technology-Hellas (FORTH)
Inter-University Centre for Astronomy and Astrophysics
Konstantinos Tassis
University of Crete
Foundation for Research and Technology-Hellas (FORTH)
D. Blinov
Foundation for Research and Technology-Hellas (FORTH)
S. Kiehlmann
Foundation for Research and Technology-Hellas (FORTH)
E. Koutsiona
University of Crete
S. Maharana
South African Astronomical Observatory
S. Romanopoulos
Foundation for Research and Technology-Hellas (FORTH)
University of Crete
R. Skalidis
California Institute of Technology (Caltech)
A. Vervelaki
University of Crete
S. E. Clark
Kavli Institute for Particle Astrophysics and Cosmology
Stanford University
J. A. Kypriotakis
University of Crete
Foundation for Research and Technology-Hellas (FORTH)
A. C.S. Readhead
Foundation for Research and Technology-Hellas (FORTH)
California Institute of Technology (Caltech)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 684 A132Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.1051/0004-6361/202348099