J/ApJS/160/220 Full-polarization observations of OH masers (Fish+, 2005)
Full-polarization observations of OH masers in massive star-forming regions.
I. Data.
Fish V.L., Reid M.J., Argon A.L., Zheng X.-W.
<Astrophys. J. Suppl. Ser., 160, 220-271 (2005)>
=2005ApJS..160..220F 2005ApJS..160..220F (SIMBAD/NED BibCode)
ADC_Keywords: Masers ; Radio lines ; Interstellar medium ; Polarization
Keywords: ISM: magnetic fields - masers - radio lines: ISM - stars: formation
Abstract:
We present full-polarization VLBA maps of the ground-state, main-line,
2Π3/2, J=3/2 OH masers in 18 Galactic massive star-forming regions.
This is the first large polarization survey of interstellar hydroxyl
masers at VLBI resolution. A total of 184 Zeeman pairs are identified,
and the corresponding magnetic field strengths are indicated. We also
present spectra of the NH3 emission or absorption in these
star-forming regions.
Description:
We observed 18 sources in 5 separate epochs with the National Radio
Astronomy Observatory's Very Long Baseline Array (VLBA). Sixteen of
the sources were observed at the frequencies of both main-line
2Π3/2, J=3/2 OH transitions (1665.4018 and 1667.3590MHz) using
125kHz bands divided into 128 spectral channels, which corresponds to
a velocity width of 0.176km/s per channel. W51 and G351.775-0.538
were observed using 250kHz bands instead, resulting in a velocity
width of 0.352km/s per channel. Both the parallel and
cross-polarization data were correlated in order to produce images in
all Stokes parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 171 18 Observed sources
refs.dat 41 14 References
table2.dat 92 111 G5.886-0.393
table3.dat 92 58 G9.622+0.195
table4.dat 92 23 G10.624-0.385
table5.dat 92 147 G34.257+0.154
table6.dat 92 26 G35.577-0.029
table7.dat 92 45 G40.622-0.137
table8.dat 92 86 G43.796-0.127
table9.dat 92 108 G49.488-0.387 (W51 e1)
table10.dat 92 98 G49.488-0.387 (W51 e2)
table11.dat 92 63 G69.540-0.976 (ON 1)
table12.dat 92 17 G70.293+1.601 (K3-50)
table13.dat 92 96 G75.782+0.343 (ON 2 N)
table14.dat 92 92 G81.721+0.571 (W75 S)
table15.dat 92 204 G81.871+0.781 (W75 N)
table16.dat 92 84 G109.871+2.114 (Cep A)
table17.dat 92 52 G111.543+0.777 (NGC 7538)
table18.dat 92 25 G196.454-1.677 (S269)
table19.dat 92 33 G213.706-12.60 (Mon R2)
table20.dat 92 73 G351.775-0.538
table21.dat 98 184 Zeeman pairs
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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- 14 A14 --- [ARM2000] Source name
16- 23 A8 --- OName Other name
25- 26 I2 h RAh Hour of Right Ascension (J2000.0)
28- 29 I2 min RAm Minute of Right Ascension (J2000.0)
31- 35 F5.2 s RAs Second of Right Ascension (J2000.0)
37 A1 --- DE- Sign of the Declination (J2000.0)
38- 39 I2 deg DEd Degree of Declination (J2000.0)
41- 42 I2 arcmin DEm Arcminute of Declination (J2000.0)
44- 47 F4.1 arcsec DEs Arcsecond of Declination (J2000.0)
49- 52 F4.1 kpc Dist Distance
54 I1 --- Epoch Epoch of observation (1)
56- 58 I3 min ObsTime Approximate amount of total on-source
observing time
60- 61 I2 --- r_Dist Reference on Dist
63- 85 A23 --- Tables Name of the table(s) containing maser data
87-128 A42 --- Beam1665 Beam characteristics at 1665MHz
130-171 A42 --- Beam1667 Beam characteristics at 1667MHz
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Note (1): Epoch of observation, defined as follows:
1 = 1996 March 01-02
2 = 2000 November 22 and 2001 January 06
3 = 2001 February 16-17
4 = 2001 May 26 and 2001 May 28
5 = 2002 February 06
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- Bibcode Bibcode
24- 41 A18 --- Aut Author's name
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Byte-by-byte Description of file: table[2-9].dat table1?.dat table20.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Maser feature (1)
5- 12 F8.2 mas EOff East offset (ΔθX) from the source
14- 21 F8.2 mas NOff North offset (ΔθY) from the source
23- 28 F6.2 km/s Vel ? Velocity
30- 33 F4.2 km/s DeltaVel ? Velocity FWHM
35- 40 F6.2 Jy SRCP ? Right hand Circular Polarization (Stokes RR)
peak flux density
42- 47 F6.2 Jy SLCP ? Left hand Circular Polarization (Stokes LL)
peak flux density
49- 54 F6.2 Jy Slin ? Linear [(Q2+U2)1/2] polarization peak
flux density
56- 59 F4.2 --- mL ? Linear polarization fraction
61- 63 I3 deg PPA ? Polarization position angle
65- 70 F6.2 mas Maj Spot fit parameter Maj
72- 76 F5.2 mas Min Spot fit parameter Min
78- 80 I3 deg Theta Position angle
82- 87 F6.1 10+9K Tpeak Minimum peak brightness temperature
89- 92 I4 MHz Freq Frequency
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Note (1): When the same maser line is seen in more than one polarization, as is
the case for spots with a high degree of linear polarization or a
substantial unpolarized component, all relevant parameters except the
linear polarization fraction and position angle are given for each
polarization, and the entries are grouped together on adjacent lines.
Thus, any maser line is represented by one to three lines of the
table, depending on its polarization characteristics.
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Byte-by-byte Description of file: table21.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- [ARM2000] Source name
16 A1 --- f_[ARM2000] [c] Flag on Name (1)
18- 25 A8 --- OName Other name
27- 30 I4 MHz Freq Frequency
32- 39 F8.2 mas DelXR Right hand Circular Polarization X offset
41 A1 --- f_DelXR [b] Flag on DelXR (2)
43- 50 F8.2 mas DelYR Right hand Circular Polarization Y offset
52- 57 F6.2 km/s VelR Right hand Circular Polarization velocity
59- 66 F8.2 mas DelXL Left hand Circular Polarization X offset
68- 75 F8.2 mas DelL Left hand Circular Polarization Y offset
77- 82 F6.2 km/s VelL Left hand Circular Polarization velocity
84- 87 F4.1 10-7T B Magnetic field in units of milliGauss
89- 92 F4.1 mas SepAng Angular separation (3)
94- 98 F5.1 AU SepLin Linear separation (3)
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Note (1): A "c" indicates that the listed separations for G351.775-0.538 may be
overestimates due to the large synthesized beam.
Note (2): A "b" indicates a Zeeman triplet.
Note (3): Angular and linear separation between LCP and RCP components of Zeeman
pair. Pairs whose separation is much greater than ∼70AU may be less
reliable indicators of magnetic field strength and direction than the
others.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Marianne Brouty [CDS] 29-May-2006