J/ApJ/953/21 Inverse MultiView. II. 6.7GHz methanol masers (Hyland+, 2023)
Inverse MultiView.
II. Microarcsecond trigonometric Parallaxes for Southern Hemisphere 6.7GHz
methanol masers G232.62+00.99 and G323.74-00.26.
Hyland L.J., Reid M.J., Orosz G., Ellingsen S.P., Weston S.D., Kumar J.,
Dodson R., Rioja M.J., Hankey W.J., Yates-Jones P.M., Natusch T.,
Gulyaev S., Menten K.M., Brunthaler A.
<Astrophys. J., 953, 21 (2023)>
=2023ApJ...953...21H 2023ApJ...953...21H
ADC_Keywords: Interferometry; Masers; Radio lines
Keywords: Astrophysical masers ; Radio astrometry ;
Very long baseline interferometry
Abstract:
We present the first results from the Southern Hemisphere Parallax
Interferometric Radio Astrometry Legacy Survey: 10µas accurate
parallaxes and proper motions for two Southern Hemisphere 6.7GHz
methanol masers obtained using the inverse MultiView calibration
method. Using an array of radio telescopes in Australia and New
Zealand, we measured trigonometric parallaxes and proper motions for
the masers associated with the star formation region G232.62+00.99 of
π=0.610±0.011mas, µx=-2.266±0.021mas/yr, and
µy=2.249±0.049mas/yr, which implies its distance to be
d=1.637±0.029kpc. These measurements represent an improvement in
accuracy by more than a factor of 3 over the previous measurements
obtained through Very Long Baseline Array observations of the 12GHz
methanol masers associated with this region. We also measure the
trigonometric parallax and proper motion for G323.74-00.26 as
π=0.364±0.009mas, µx=-3.239±0.025mas/yr, and
µy=-3.976±0.039mas/yr, which implies a distance of
d=2.747±0.068kpc. These are the most accurate measurements of
trigonometric parallax obtained for 6.7GHz class II methanol masers to
date. We confirm that G232.62+00.99 is in the Local Arm and find that
G323.74-00.26 is in the Scutum-Centaurus arm. We also investigate the
structure and internal dynamics of both masers.
Description:
The VLBI array used for the observations of the two class II 6.7GHz
masers G232.62+00.99 and G323.74-00.26 is shown in Figure 4,
comprising the University of Tasmania telescopes Ceduna 30m (Cd),
Hobart 12m (Hb), and Katherine 12m (Ke) and the Auckland University of
Technology telescope Warkworth 30m (Wa). This array has a maximum
baseline length of 4750km. We recorded data at 1024Mbps in dual
polarization, Nyquist sampled at 2 bits sample-1, over the frequency
range 6580-6708GHz.
See Section 2.
Objects:
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RA (ICRS) DE Designation(s)
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07 32 09.78 -16 58 12.8 G232.62+00.99 = Caswell CH3OH 232.62+00.99
15 31 45.45 -56 30 50.1 G323.74-00.26 = Caswell CH3OH 323.74-00.26
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig1.dat 49 500 Auto- and cross-correlated spectra of G232.62+00.99
maser emission at epoch 6
fig2.dat 56 1000 Auto- and cross-correlated spectra of G323.74-00.26
maser emission at epoch 4.
fig7.dat 45 8 Map of methanol maser spots in G232.62+00.99 and
their proper motions relative to the reference
spot at (0,0)
fig8.dat 45 207 Map and dynamics of maser spots in G323.74-00.26
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See also:
VIII/96 : 6-GHz methanol multibeam maser catalogue (Caswell+, 2010-12)
J/A+AS/25/25 : HII regions of the Northern Milky Way (Dubout-Crillon+ 1976)
J/MNRAS/377/571 : GLIMPSE methanol masers non-detections (Ellingsen+, 2007)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/MNRAS/485/88 : Southern compact extragalactic radio sources (Petrov+, 2019)
J/ApJ/885/131 : ∼200 high-mass SFR plx & PMs with VLBI (Reid+, 2019)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.2 km/s Vel [-27.3/60.4] Velocity
8- 13 F6.2 Jy Auto [639.5/887.5] Scalar-averaged, autocorrelated
baseline flux density for all telescopes
15- 19 F5.2 Jy Cd-Hb [17.3/73] Ceduna 30m and Hobart 12m baseline
flux density
21- 25 F5.2 Jy Cd-Ke [17.8/87] Ceduna 30m and Katherine 12m baseline
flux density
27- 31 F5.2 Jy Cd-Wa [7.9/40] Ceduna 30m and Warkworth 30m baseline
flux density
33- 37 F5.2 Jy Hb-Ke [34.8/45.4] Hobart 12m and Katherine 12m
baseline flux density
39- 43 F5.2 Jy Hb-Wa [15.7/55.2] Hobart 12m and Warkworth 30m
baseline flux density
45- 49 F5.2 Jy Ke-Wa [16/28] Katherine 12m and Warkworth 30m baseline
flux density
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Byte-by-byte Description of file: fig2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 6 F6.2 km/s Vel [-94/-6.1] Velocity
8- 14 F7.2 Jy Auto [625/3699] Scalar-averaged, autocorrelated
baseline flux density for all telescopes
16- 21 F6.2 Jy Cd-Hb [35.2/520.4] Ceduna 30m and Hobart 12m baseline
flux density
23- 28 F6.2 Jy Cd-Ke [31/549.1] Ceduna 30m and Katherine 12m baseline
flux density
30- 35 F6.2 Jy Cd-Wa [10.8/601] Ceduna 30m and Warkworth 30m baseline
flux density
37- 42 F6.2 Jy Hb-Ke [88.5/313.4] Hobart 12m and Katherine 12m
baseline flux density
44- 49 F6.2 Jy Hb-Wa [31.7/626.1] Hobart 12m and Warkworth 30m
baseline flux density
51- 56 F6.2 Jy Ke-Wa [27.7/355] Katherine 12m and Warkworth 30m
baseline flux density
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Byte-by-byte Description of file: fig7.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 km/s Vel [21.8/23.1] Spot LoS velocity
8- 14 F7.4 mas X X coordinate position
16- 23 F8.4 mas Y Y coordinate position
25- 31 F7.4 mas/yr Vx X position spot velocity
33- 39 F7.4 mas/yr Vy Y position spot velocity
41- 45 F5.2 Jy I [2/77.5] Spot flux density
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Byte-by-byte Description of file: fig8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.3 km/s Vel [-53.52/-47.8] Spot LoS velocity
9- 16 F8.3 mas X X coordinate position
18- 24 F7.3 mas Y Y coordinate position
26- 31 F6.3 mas/yr Vx X position spot velocity
33- 38 F6.3 mas/yr Vy Y position spot velocity
40- 45 F6.2 Jy I [1.39/438] Spot flux density
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History:
From electronic version of the journal
References:
Hyland et al. Paper I. 2022ApJ...932...52H 2022ApJ...932...52H
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Sep-2025