J/A+A/695/A101 Faraday moments of STAPS (Raycheva+, 2025)
Faraday moments of the Southern Twenty-centimeter All-sky Polarization
Survey (STAPS).
Raycheva N., Haverkorn M., Ideguchi S., Stil J.M., Sun X., Han J.L.,
Carretti E., Gao X.Y., Bracco A., Clark S.E., Dickey J.M., Gaensler B.M.,
Hill A., Landecker T., Ordog A., Seta A., Tahani M., Wolleben M.
<Astron. Astrophys. 695, A101 (2025)>
=2025A&A...695A.101R 2025A&A...695A.101R (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Magnetic fields ; Polarization
Keywords: polarization - ISM: magnetic fields
Abstract:
Faraday tomography of broadband radio polarization
surveys enables us to study magnetic fields and their interaction with
the interstellar medium (ISM). Such surveys include the Global
Magneto-Ionic Medium Survey (GMIMS), which covers the northern and
southern hemispheres at ∼300-1800MHz.
In this work, we used the GMIMS High Band South (1328-1768MHz),
also named the Southern Twenty-centimeter All-sky Polarization Survey
(STAPS), which observes the southern sky at a resolution of 18°.
To extract the key parameters of the magnetized ISM from STAPS, we
computed the Faraday moments of the tomographic data cubes. These
moments include the total polarized intensity, the mean Faraday depth
weighted by the polarized intensity, the weighted dispersion of the
Faraday spectrum, and its skewness. We compared the Faraday moments to
those calculated over the same frequency range in the northern sky
(using the Dominion Radio Astrophysical Observatory, DRAO), in a strip
of 360°x30° that overlaps with STAPS coverage.
We find that the total polarized intensity is generally
dominated by diffuse emission that decreases at longitudes of
l≤300°. The Faraday moments reveal a variety of polarization
structures. Low-intensity regions at high latitudes usually have a
single Faraday depth component. Due to its insufficiently large
frequency coverage, STAPS cannot detect Faraday thick structures.
Comparing the Faraday depths from STAPS to total rotation measures
from extragalactic sources suggests that STAPS frequencies are high
enough that the intervening ISM causes depolarization to background
emission at intermediate and high Galactic latitudes. Where they
overlap, the STAPS and DRAO surveys exhibit broad correspondence but
differ in polarized intensity by a factor of ∼1.8
Description:
The STAPS observations were made with the 64m Parkes
telescope Murriyang using an H-OH receiver. The S-PASS Galileo
receiver was placed in prime focus, and the H-OH receiver was located
off-axis next to the Galileo receiver, displaced 630 mm from the prime
focus horizontally, and 7.6 mm vertically to keep the feed in focus.
In this way, STAPS was able to piggyback on the S-PASS survey without
requiring additional observing time, with some penalty in the form of
beam distortions (see below). The complete survey and data products
is presented by Sun et al. (2025A&A...694A.169S 2025A&A...694A.169S, Cat. J/A+A/694/A169).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 52 3 List of fits maps
fits/* . 3 Individual fits maps
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See also:
J/A+A/694/A169 : STAPS images (Sun+, 2025)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Nx Number of pixels along X-axis
6- 9 I4 --- Ny Number of pixels along Y-axis
11- 16 I6 Kibyte size Size of FITS file
18- 24 A7 --- FileName Name of FITS file, in subdirectory fits
26- 52 A27 --- Title Title of the FITS file
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History:
From Marijke Haverkorn, m.haverkorn(at)astro.ru.nl
Acknowledgements:
This work is part of the joint NWO-CAS research programme in the field
of radio astronomy with project number 629.001.022, which is (partly)
financed by the Dutch Research Council (NWO). We thank Karel D.
Temmink for the help with coding/parallelization in the astronomy
department's coma computing cluster. MH acknowledges funding from
the European Research Council (ERC) under the European Union's
Horizon 2020 research and innovation programme (grant agreement No
772663). JMS acknowledges the support of the Natural Sciences and
Engineering Research Council of Canada (NSERC), 2019-04848. XHS, JLH
and XYG are supported by the International Partnership Program of
Chinese Academy of Sciences, Grant No. 114A11KYSB20170044. The Dunlap
Institute is funded through an endowment established by the David
Dunlap family and the University of Toronto. AO is partly supported by
the Dunlap Institute. BMG acknowledges the support of the Natural
Sciences and Engineering Research Council of Canada (NSERC) through
grant RGPIN-2022-03163, and of the Canada Research Chairs program. AB
acknowledges financial support from the INAF initiative "IAF Astronomy
Fellowships in Italy" (grant name MEGASKAT). MT is supported by the
Banting Fellowship (Natural Sciences and Engineering Research Council
Canada) hosted at Stanford University and the Kavli Institute for
Particle Astrophysics and Cosmology (KIPAC) Fellowship. The authors
acknowledge Interstellar Institute's program "With Two Eyes" and the
Paris-Saclay University's Institute Pascal for hosting discussions
that nourished the development of the ideas behind this work. This
work made use of Astropy3 a community-developed core Python package
for Astronomy (Astropy Collaboration et al. 2018) and Python modules
of Matplotlib4 (Hunter 2007), NumPy5 (Oliphant 2006; van der Walt et
al. 2011), and SciPy6 (Virtanen et al. 2020). This research made use
of the software package Montage7. Parts of this work's results use
the color maps in the CMasher package (van der Velden 2020). The
Parkes 64m radio-telescope (Murriyang) is part of the Australia
Telescope National Facility 8 which is funded by the Australian
Government for operation as a National Facility managed by CSIRO. We
acknowledge the Wiradjuri people as the Traditional Owners of the
Observatory site.
References:
Sun et al., 2025A&A...694A.169S 2025A&A...694A.169S, Cat. J/A+A/694/A169
The Southern Twenty-centimetre All-sky Polarization Survey (STAPS):
Survey description and maps
(End) Patricia Vannier [CDS] 28-Feb-2025