J/MNRAS/439/2584 Southern methanol masers at 36 and 44GHz (Voronkov+, 2014)
Southern class I methanol masers at 36 and 44 GHz.
Voronkov M.A., Caswell J.L., Ellingsen S.P., Green J.A., Breen S.L.
<Mon. Not. R. Astron. Soc. 439, 2584 (2014)>
=2014MNRAS.439.2584V 2014MNRAS.439.2584V
ADC_Keywords: Masers ; Radio lines ; Positional data
Keywords: masers - stars: formation - HII regions - ISM: jets and outflows -
ISM: molecules - photodissociation region (PDR)
Abstract:
The Australia Telescope Compact Array (ATCA) has been used for high
angular resolution imaging of 71 southern class I methanol maser
sources quasi-simultaneously at 36 and 44GHz. The data reveal a high
level of morphological and kinematical complexity, and allow us to
demonstrate associations, at arcsecond precision, of the class I maser
emission with outflows, expanding HII regions, dark clouds, shocks
traced by the 4.5-micron emission and 8.0-micron filaments. More than
700 maser component features were found at each of the two methanol
transitions, but with only 23 per cent recognisable at both
transitions; the morphology of class I emission is much better
revealed by our survey of both transitions, compared with either one
alone. We found that the number of masers falls exponentially with the
projected linear distance from the associated class II 6.7-GHz
methanol maser. This distribution has a scale of 263±15-milliparsec,
irrespective of the transition. The class I masers associated with OH
masers were found to have a tendency to be more spread out, both
spatially and in the velocity domain. This is consistent with the
expectation that such sources are more evolved. Apart from a small
number of high-velocity components (which are largely blue-shifted and
predominantly seen at 36GHz), the velocity distribution was found to
be Gaussian, peaking near the systemic velocity of the region, which
had been estimated as the middle of the velocity interval of the
associated class II methanol maser at 6.7GHz. The mean indicated a
small, but significant blue shift asymmetry of -0.57km/s
(uncertainties are 0.06 and 0.07km/s for the 36- and 44-GHz masers,
respectively) with respect to the 6.7GHz masers. The standard
deviation of the velocity distribution was found to be 3.65±0.05
and 3.32±0.07km/s for the 36- and 44GHz masers, respectively. We
also suggest a refined rest frequency value of 36169.238±0.011MHz
for the 4-1-30E methanol transition.
Description:
The catalogue includes absolute positions and spectral parameters
(peak radial velocity, peak flux density and width) of individual
spectral features detected in methanol maser transitions at 36 and
44GHz. With the exception of three absorption components (one at 36GHz
and two at 44GHz), all the remaining entries represent emission (which
can be quasi-thermal in the case of weak and broad components). Each
entry in the catalogue represent a single Gaussian component in the
velocity domain. The absolute positions were determined for each
Gaussian component by fitting the point source model.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 71 Observation details for all targets
table3.dat 97 1729 Fit parameters for individual maser features at
36 and 44GHz in 71 southern sources
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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- 12 A12 --- Name Source name, GLLL.ll+B.bb
13 A1 --- n_Name [*] Sources with better accuracy (1)
15- 16 I2 h RAh Pointing centre Right Ascension (J2000)
18- 19 I2 min RAm Pointing centre Right Ascension (J2000)
21- 24 F4.1 s RAs Pointing centre Right Ascension (J2000)
26 A1 --- DE- Pointing centre Declination sign (J2000)
27- 28 I2 deg DEd Pointing centre Declination (J2000)
30- 31 I2 arcmin DEm Pointing centre Declination (J2000)
33- 34 I2 arcsec DEs Pointing centre Declination (J2000)
36- 41 A6 --- Date1 Observation date (MMM DD, 2007)
43- 45 I3 mJy noise36 [54/120] 36GHz 1σ noise
47- 50 I4 km/s Vel36l Lower value of velocity range for 36GHz
51 A1 --- --- [,]
53- 55 I3 km/s Vel36u Upper value of velocity range for 36GHz
57- 62 A6 --- Date2 Observation date (MMM DD, 2007)
64- 66 I3 mJy noise44 [81/270] 44GHz 1σ noise
68- 71 I4 km/s Vel44l Lower value of velocity range for 44GHz
72 A1 --- --- [,]
74- 76 I3 km/s Vel44u Upper value of velocity range for 44GHz
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Note (1): Note as follows:
* = sources observed using the same frequency configuration as the primary
calibrator observations and potentially have better than average flux
density accuracy
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name, GLLL.ll+B.bb
14- 15 A2 --- m_Name Label for the particular location in the given
source, used only for cross-referencing
17- 18 I2 GHz Freq [36/44] Frequency of the molecular transition,
either 36 or 44 (GHz)
20- 27 F8.3 km/s Vel [-107/20] Peak velocity
29- 33 F5.3 km/s e_Vel [0/6.3] Peak velocity uncertainty
35- 36 I2 h RAh Right Ascension J2000 (hours)
38- 39 I2 min RAm Right Ascension J2000 (minutes)
41- 46 F6.3 s RAs Right Ascension J2000 (seconds)
48- 52 F5.3 s e_RAs Right Ascension uncertainty (seconds)
54 A1 --- DE- Declination J2000 (sign)
55- 56 I2 deg DEd Declination J2000 (degrees)
58- 59 I2 arcmin DEm Declination J2000 (arcminutes)
61- 66 F6.3 arcsec DEs Declination J2000 (arcseconds)
68- 72 F5.3 arcsec e_DEs Declination uncertainty (arcseconds)
74- 78 F5.3 km/s FWHM Full width at half maximum
80- 84 F5.3 km/s e_FWHM Uncertainty of the full width at half maximum
86- 91 F6.2 Jy Flux Peak flux density
93- 97 F5.2 Jy e_Flux Uncertainty of the flux density
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Acknowledgements:
Maxim Voronkov, Maxim.Voronkov(at)csiro.au
(End) Maxim Voronkov [CSIRO, Australia], Patricia Vannier [CDS] 27-Feb-2014