J/A+A/684/A162 Starlight-polarization-based tomography (Pelgrims+, 2024)
The first degree-scale starlight-polarization-based tomography map of the
magnetized interstellar medium.
Pelgrims V., Mandarakas N., Skalidis R., Tassis K., Panopoulou G.V.,
Pavlidou V., Blinov D., Kiehlmann S., Clark S.E., Hensley B.S.,
Romanopoulos S., Basyrov A., Eriksen H.K., Falalaki M., Ghosh T.,
Gjerlow E., Kypriotakis J.A., Maharana S., Papadaki A., Pearson T.J.,
Potter S.B., Ramaprakash A.N., Readhead A.C.S., Wehus I.K.
<Astron. Astrophys. 684, A162 (2024)>
=2024A&A...684A.162P 2024A&A...684A.162P (SIMBAD/NED BibCode)
ADC_Keywords: Polarization ; Interstellar medium ; Optical
Keywords: polarization - methods: statistical - dust, extinction -
ISM: magnetic fields - ISM: structure
Abstract:
We present the first degree-scale tomography map of the dusty
magnetized interstellar medium (ISM) from stellar polarimetry and
distance measurements. We used the RoboPol polarimeter at Skinakas
Observatory to conduct a survey of the polarization of starlight in a
region of the sky of about four square degrees. We propose a Bayesian
method to decompose the stellar-polarization source field along the
distance to invert the three-dimensional (3D) volume occupied by the
observed stars. We used this method to obtain the first 3D map of the
dusty magnetized ISM. Specifically, we produced a tomography map of
the orientation of the plane-of-sky component of the magnetic field
threading the diffuse, dusty regions responsible for the stellar
polarization. For the targeted region centered on Galactic coordinates
(l, b) (103.3deg, 22.3deg), we identified several ISM clouds. Most of
the lines of sight intersect more than one cloud. A very nearby
component was detected in the foreground of a dominant component from
which most of the polarization signal comes and which we identified as
being an intersection of the wall of the Local Bubble and the Cepheus
Flare. Farther clouds, with a distance of up to 2kpc, were similarly
detected. Some of them likely correspond to intermediate-velocity
clouds seen in HI spectra in this region of the sky. We found that the
orientation of the plane-of-sky component of the magnetic field
changes along distance for most of the lines of sight. Our study
demonstrates that starlight polarization data coupled to distance
measures have the power to reveal the great complexity of the dusty
magnetized ISM in 3D and, in particular, to provide local measurements
of the plane-of-sky component of the magnetic field in dusty regions.
This demonstrates that the inversion of large data volumes, as
expected from the Pasiphae survey, will provide the necessary means to
move forward in the modeling of the Galactic magnetic field and of the
dusty magnetized ISM as a contaminant in observations of the cosmic
microwave background polarization.
Description:
The data table results from an optical polarization survey in R band
using the RoboPol polarimeter at Skinakas observatory between 2019 and
2022 to which is appended data from Panopoulou et al.
(2019ApJ...872...56P 2019ApJ...872...56P, Cat. J/ApJ/872/56). The table contains all stars
with successful cross-match with the Gaia DR3 catalog. See Sect. 2 of
the paper for details on the survey and the cross-match. Not all stars
have been used for the tomographic decomposition of the magnetized
interstellar medium (see usage flag and Sects. 2 and 3 in the paper).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 1698 Polarization catalogue
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/ApJ/872/56 : R-band linear polarization of Gaia stars (Panopoulou+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 identifier (source_id)
21- 29 F9.5 deg RAdeg Right Ascenssion (ICRS) at Ep=2016.0
31- 38 F8.5 deg DEdeg Declination (ICRS) at Ep=2016.0
40- 44 F5.2 % q q Stokes parameter (1)
46- 49 F4.2 % e_q Uncertainty on q
51- 55 F5.2 % u u Stokes parameter (1)
57- 60 F4.2 % e_u Uncertainty on u
62- 66 F5.2 % p Degree of polarization (2)
68- 71 F4.2 % e_p Uncertainty on p
73- 77 F5.1 deg EVPA Polarization angle (1)
79- 82 F4.1 deg e_EVPA Uncertainty on EVPA
84- 93 A10 --- date Observation date (3)
95- 99 F5.2 mag Gmag G-band magnitude
101-108 F8.4 mas plx ? Parallax
110-116 F7.4 mas e_plx ? Uncertainty on plx
118-123 F6.3 --- dMaha ? A posteriori flag for outliers (4)
125 I1 --- UsageFlag [0/2] Usage flag (5)
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Note (1): Stokes parameters are measured following the IAU convention in
equatorial celestial coordinate system, so is the polarization position
angle.
Note (2): degree of polarization are not debiased.
Note (3): observation date are "2016" for data from Panopoulou et al.
(2019ApJ...872...56P 2019ApJ...872...56P, Cat. J/ApJ/872/56) or follow the yymmdd format for
newly acquired polarization data.
Note (4): dMaha results from the a posteriori test run in Sect. 5.5 of the
paper. The higher the d_Maha value, the lower the probability that the
star's polarization is solely of interstellar origin.
dMaha is not provided for stars with missing or bad data on plx or for
stars falling outside the sky region for which tomography decomposition
is derived.
Note (5): Usage flag as follows:
0 = stars not used in the analysis (missing or bad data on plx)
1 = used in the tomography analysis
2 = flagged as a outlier candidate according the the sigma-clipping
procedure in Sect. 3 of the paper, and discarded from the tomography
analysis
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Acknowledgements:
Vincent Pergrims, vincent.pelgrims(at)ulb.be
(End) Patricia Vannier [CDS] 16-Feb-2024