J/ApJ/647/418 Ground-state OH masers in W3(OH) study (Fish+, 2006)
A very high spectral resolution study of ground-state OH masers in W3(OH).
Fish V.L., Brisken W.F., Sjouwerman L.O.
<Astrophys. J., 647, 418-431 (2006)>
=2006ApJ...647..418F 2006ApJ...647..418F
ADC_Keywords: Interstellar medium ; Masers
Keywords: ISM: individual (W3(OH)) - ISM: molecules - line: profiles - masers -
radio lines: ISM
Abstract:
We present VLBA observations of the ground-state hydroxyl masers in
W3(OH) at 0.02km/s spectral resolution. Over 250 masers are
detected, including 56 Zeeman pairs. Line shapes are predominantly
Gaussian or combinations of several Gaussians, with normalized
deviations typically of the same magnitude as in masers in other
species.
Description:
The National Radio Astronomy Observatory's Very Long Baseline Array
(VLBA) was used to observe the ground-state OH masers in two massive
star-forming regions, W3(OH) and Orion KL. Data were collected
starting at approximately 09:00 UT on 2005 September 20 using all 10
antennas.
Objects:
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RA (2000) DE Designation(s)
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02 27 04.1 +61 52 22 W3(OH) = GRS 133.90 +01.10
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 253 Detected Masers in W3(OH)
table2.dat 61 56 Zeeman Pairs in W3(OH)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [FBS2006b] [1/253] Spot number
5- 8 I4 MHz Freq Frequency
10 A1 --- Pol [LR] Left or Right circular polarization
12- 19 F8.2 mas oRA Right Ascension offset (2)
21- 28 F8.2 mas oDE Declination offset (2)
30- 35 F6.2 km/s Vel Peak emission channel LSR velocity
37- 41 F5.2 Jy Bright Peak brightness in units of Jy/beam (3)
43- 48 F6.3 km/s/mas Grad ? Velocity gradient
50- 53 I4 deg PA [-180/180]? Position angle (4)
55 A1 --- f_PA [f] f: Gradient computed over multiple peaks
57- 58 I2 --- Pair ? Zeeman pair number as listed in Table 2
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Note (2): Centroid of Gaussian fit in channel of peak emission.
See Section 3 for discussion of relative alignment of maser spots
at different frequencies and polarizations.
Note (3): Of Gaussian fit in channel of peak emission.
Note (4): East of North in direction of increasing line-of-sight velocity
across the maser spot.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Pair [1/56] Pair Number
4- 7 I4 MHz Freq Frequency
9- 15 F7.2 mas oRA1 Left circular polarisation (LCP) component
Right Ascension offset
17- 24 F8.2 mas oDE1 LCP component Declination offset
26- 31 F6.2 km/s Vel1 LCP component Peak emission channel LSR velocity
33- 39 F7.2 mas oRA2 Right circular polarisation (RCP) component
Right Ascension offset
41- 48 F8.2 mas oDE2 RCP component Declination offset
50- 55 F6.2 km/s Vel2 RCP component Peak emission channel LSR velocity
57- 60 F4.1 10-7T B Magnetic field, in mGauss (1)
61 A1 --- n_B [b] Note on B (2)
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Note (1): Assumes splitting appropriate for ±1 components for 1612 and
1720MHz transitions. Positive values indicate magnetic fields oriented
in the hemisphere pointing away from the observer.
Note (2): Large separation between LCP and RCP components. These may be
Zeeman cousins as defined in Fish & Reid (2006ApJS..164...99F 2006ApJS..164...99F).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Jul-2008