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J/MNRAS/291/261 Methanol maser survey of IRAS-selected sources (Walsh+ 1997)
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Studies of ultracompact H II regions.
I. Methanol maser survey of IRAS-selected sources.
Walsh A.J., Hyland A.R., Robinson G., Burton M.G
<Mon. Not. R. Astron. Soc. 291, 261 (1997)>
=1997MNRAS.291..261W (SIMBAD/NED BibCode)
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ADC_Keywords: H II regions ; Masers ; Radial velocities
Keywords: surveys - stars: formation - H II regions - ISM: molecules -
radio lines: ISM
Abstract:
A survey of ultracompact (UC) HII regions has been carried out by
searching for 6.669-GHz methanol maser emission from a sample of 535
IRAS-selected candidates. A total of 201 candidates exhibit methanol
emission. These sources have been used, in conjunction with previously
identified UC HII regions, to provide a base for further studies of
such regions. Estimates of distances have indicated that the
identified UC HII regions tend to have some Galactic structure but it
is not clear whether they lie in or between the spiral arms of the
Galaxy. The regions are tightly constrained to the plane of the
Galaxy. Comparison of identified regions and IRAS sources selected by
Wood & Churchwell indicates that there there is some degree of
contamination, which could be due to an older phase in the life on an
UC HII region where methanol maser emission is not apparent.
Luminosities and spectral types have been derived for many of the
regions. The maximum number of maser spots observed seems to increase
with increasing peak maser luminosity, which indicates that the maser
emission is more dependent on the abundance of methanol than the
availability of far-infrared radiation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 11 322 IRAS sources in our data set with no positive
methanol identification, and no other defining
UC H II characteristics
table2.dat 115 215 List of the 215 candidates identified as
UC H II regions
tables.tex 132 371 LaTeX version of the tables
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See also:
J/ApJS/91/659 : Ultracompact HII regions radio images (Kurtz+ 1994)
J/A+AS/110/81 : Methanol masers towards IRAS sources (van der Walt+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- IRAS IRAS PSC name (Cat. <II/125>)
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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- 11 A11 --- IRAS IRAS PSC name (Cat. <II/125>)
13- 19 F7.3 deg GLON Galactic longitude of pointing centre (1)
21- 28 F8.3 deg GLAT Galactic latitude of pointing centre (1)
30- 36 F7.2 Jy Peak ? Peak flux density of methanol
maser emission
37- 38 A2 --- n_Peak [abg ] Note on observation of Peak (2)
40- 45 F6.1 km/s RV ? Radial velocity of Peak maser component
47- 50 I4 km/s Vinf ? Velocity range over which maser emission
is seen (lower value)
52- 55 I4 km/s Vsup ? Velocity range over which maser emission
is seen (upper value)
56 A1 --- n_Vsup [d] Note on Velocity range (3)
58- 59 I2 --- Npeak ? Number of maser peaks observed in each
spectrum
61- 64 F4.1 kpc Dist ? Adopted kinematic distance (4)
66- 69 F4.1 kpc Dist2 ?Second kinematic distance when ambiguity
70 A1 --- r_Dist [iez] Source of Dist (5)
72- 79 F8.4 10+4solLum Ltot ? Calculated total luminosity for IRAS
fluxes form Dist value
82- 88 F7.2 10+4solLum Ltot2 ? Calculated total Luminosity for IRAS
fluxes from Dist2 value
89- 92 A4 --- SpType Spectral type of single star responsible
for emission in Ltot
94- 97 A4 --- SpType2 Spectral type of single star responsible
for emission in Ltot2
99 A1 --- Ass1 [MNOUW] Other association (6)
100-102 A3 --- r_Ass1 Source of Ass1 (7)
104 A1 --- Ass2 [MNOUWx] Other association (6)
105-107 A3 --- r_Ass2 Source of Ass2 (7)
109 A1 --- Ass3 [MOUWx] Other association (6)
110-112 A3 --- r_Ass3 Source of Ass3 (7)
114 A1 --- Ass4 [W] Other association (6)
115 A1 --- r_Ass4 Source of Ass4 (7)
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Note (1): Galactic coordinates are shown in degrees and are derived from the
(B1950) positions or from Caswell et al. (1995MNRAS.272...96C),
where the data of Caswell et al. has been used in columns
Peak to Npeak (see Note (2))
Note (2): The methanol maser data provided in columns Peak to Npeak come from
three different observation times.
a: Data obtained during the period 24-27 September 1993
b: Data obtained during the period 8-12 April 1994 and
the remaining is that published by
Caswell et al. (1995MNRAS.272...96C)
g: Object also been observed by Schutte et al. (1993MNRAS.261..783S)
A comparison indicates that our observation position was not
accurately centred on the maser emission, since our maser peak flux
densities are substantially lower than that of
Schutte et al. (1993MNRAS.261..783S)
Note (3): d: Source that probably have more than one methanol emission peak,
due to the broad velocity range, but only one maser spot can be
unambiguously identified in the spectrum.
Note (4): The distances given are determined kinematically, using the methanol
maser velocity, except for those sources where r_Dist = e or z.
The distances obtained from previous papers tend to agree
approximately with our kinematic distance where the kinematic
distance could be measured.
Note (5): e: Distances obtained from Table 4 of
Wood & Churchwell (1989ApJS...69..831W)
z: Distances obtained from Table 2 of Kurtz et al.
(1994, Cat. <J/ApJS/91/659>)
i: Sources that have no distance estimate due to the large
uncertainties
Note (6): M: previous methanol maser detection
O: previous OH maser detection
W: previous water maser detection
U: previous identification by a compact radio source
N: sources discovered in this paper or reported in
Walsh et al. (1995PASA...12..186W)
x: non-detection in methanol emission by us
Note (7): e: Henning et al. (1992A&AS...93..525H)
f: Kurtz et al. (1994, Cat. <J/ApJS/91/659>)
g: Churchwell (1990A&ARv...2...79C)
h: Wood & Churchwell (1989ApJS...69..831W)
j: Caswell et al. (1995MNRAS.272...96C)
k: Braz et al. (1990A&A...236..479B)
l: MacLeod & Gaylard (1992MNRAS.256..519M)
m: Schutte et al. (1993MNRAS.261..783S)
n: van der Walt et al. (1995, Cat. <J/A+AS/110/81>)
p: Caswell et al. (1995MNRAS.277..210C)
q: Norris et al. (1987ApJ...321L.159N)
r: Kemball et al. (1988ApJ...331L..37K)
s: Ellingsen et al. (1996MNRAS.280..378E)
t: Forster & Caswell (1989A&A...213..339F)
u: Cesaroni et al. (1991A&A...252..278C)
v: Palla et al. (1991A&A...246..249P)
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Acknowledgements: Andrew Walsh <ajw@newt.phys.unsw.edu.au>
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(End) Patricia Bauer [CDS] 14-Nov-1997