J/ApJ/961/13 Rc-band polarimetric survey in Sgr spiral arm (Doi+, 2024)
Tomographic imaging of the Sagittarius spiral arm's magnetic field structure.
Doi Y., Nakamura K., Kawabata K.S., Matsumura M., Akitaya H., Coude S.,
Rodrigues C.V., Kwon J., Tamura M., Tahani M., Magalhaes A.M.,
Santos-Lima R., Angarita Y., Versteeg J., Haverkorn M., Hasegawa T.,
Sadavoy S., Arzoumanian D., Bastien P.
<Astrophys. J., 961, 13 (2024)>
=2024ApJ...961...13D 2024ApJ...961...13D
ADC_Keywords: Galaxies, optical; Polarization; Stars, distances; Extinction
Keywords: Interstellar magnetic fields ; Interstellar medium ;
Milky Way magnetic fields ; Polarimetry ; Spiral arms
Abstract:
The Galactic global magnetic field is thought to play a vital role in
shaping Galactic structures such as spiral arms and giant molecular
clouds. However, our knowledge of magnetic field structures in the
Galactic plane at different distances is limited, as measurements used
to map the magnetic field are the integrated effect along the line of
sight. In this study, we present the first ever tomographic imaging of
magnetic field structures in a Galactic spiral arm. Using optical
stellar polarimetry over a 17'x10' field of view, we probe the
Sagittarius spiral arm. Combining these data with stellar distances
from the Gaia mission, we can isolate the contributions of five
individual clouds along the line of sight by analyzing the polarimetry
data as a function of distance. The observed clouds include a
foreground cloud (d<200pc) and four clouds in the Sagittarius arm at
1.23, 1.47, 1.63, and 2.23kpc. The column densities of these clouds
range from 0.5 to 2.8x1021cm-2. The magnetic fields associated
with each cloud show smooth spatial distributions within their
observed regions on scales smaller than 10pc and display distinct
orientations. The position angles projected on the plane of the sky,
measured from the Galactic north to the east, for the clouds in
increasing order of distance are 135°, 46°, 58°, 150°,
and 40°, with uncertainties of a few degrees. Notably, these
position angles deviate significantly from the direction parallel to
the Galactic plane.
Description:
We obtained linear polarimetry in the Cousins R band (RC band:
λ=0.65um) using the Hiroshima Optical and Near-infrared Camera
(HONIR) on the 1.5m Kanata Telescope, Higashi-Hiroshima Observatory,
on 2021 August 5. We obtained a total of 36 exposures, with each
exposure lasting 75s.
We covered the target field in Sagittarius arm using two adjacent FOVs
centered at GLON=+14.11°,GLAT=-1.41° and
GLON=+14.18°,GLAT=-1.53°. The combined FOV size was 17.0'x10.5'
as shown in Figure 1. See Section 2.2 for further explanations.
The data used for the analysis are the Gaia DR3 catalog stars and
their optical polarization data, which are shown in Table 6. The data
consist of 313 stars within the observed FOV. Among them, optical
polarimetry data is available for 184 stars, and AG values are
available for 259 stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 159 313 Data identification (Appendix B)
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See also:
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
J/ApJS/208/20 : Nine-year WMAP point source catalogs (Bennett+, 2013)
J/ApJ/834/57 : MW molecular clouds from 12CO (Miville-Deschenes+, 2017)
J/ApJS/234/11 : Pulsar rotation measures (Han+, 2018)
J/A+A/625/A135 : Gal. interstellar dust Gaia-2MASS 3D maps (Lallement+, 2019)
J/ApJ/872/56 : R-band linear polarization of Gaia stars (Panopoulou+, 2019)
J/ApJ/885/131 : High-mass SFR plx & proper motion with VLBI (Reid+, 2019)
J/MNRAS/493/351 : A large catalogue of molecular clouds (Chen+, 2020)
J/ApJS/249/23 : Gal. Plane Infrared Polarization Survey, DR4 (Clemens+, 2020)
J/ApJ/914/122 : Stellar polarimetry with Gaia DR2 data (Doi+, 2021)
Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Gaia DR3 identifier
21- 29 F9.5 deg RAdeg [275.25/275.54] Gaia DR3 Right Ascension (ICRS)
at Ep=2016.0
31- 39 F9.5 deg DEdeg [-17.43/-17.26] Gaia DR3 Declination (ICRS)
at Epoch=2016.0
41- 48 F8.5 deg GLON [14/14.3] Galactic longitude
50- 57 F8.5 deg GLAT [-1.61/-1.31] Galactic latitude
59- 65 F7.2 pc Rgeo [172.7/2980] Median distance from
Bailer-Jones+ 2021, I/352
67- 73 F7.2 pc e_Rgeo [170/2824] The 16th percentile in Rgeo
75- 81 F7.2 pc E_Rgeo [175/3136] The 84th percentile in Rgeo
83- 90 F8.5 --- qGal [-0.012/0.015]? Relative q (Q/I) Stoke parameter
in Galactic coordinates
92- 98 F7.5 --- e_qGal [0.00019/0.0042]? Uncertainty in qGal
100-107 F8.5 --- uGal [-0.023/0.016]? Relative u (U/I) Stoke parameter
in Galactic coordinates
109-115 F7.5 --- e_uGal [0.00015/0.0041]? Uncertainty in uGal
117-117 A1 --- l_P Limit flag for negative P2 values (1)
118-122 F5.3 % P [0/2.7]? Polarization fraction (1)
124-128 F5.3 % e_P [0.019/0.3]? Uncertainty in P
130-135 F6.2 deg PAGal [0.2/178.5]? Polarization position angle
in Galactic coordinates
137-141 F5.2 deg e_PAGal [0.69/99]? Uncertainty in PAGal
143-147 F5.3 mag AG [0.006/4.9]? Gaia DR3 median G band extinction
149-153 F5.3 mag b_AG [0.001/4.9]? The 16th percentile in AG
155-159 F5.3 mag B_AG [0.016/4.9]? The 84th percentile in AG
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Note (1): The debiased values of P as determined by Equation B2:
P=(qGal2+uGal2-δP2)^0.5
Due to the debiasing process, it is possible for the P2 value in
Equation (B2) to be negative. P values for data points with negative
P2 values are indicated as <0.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Mar-2026