J/A+AS/110/81 Methanol masers towards IRAS sources (van der Walt+ 1995)
New detections of 51- 60 A+-methanol masers towards IRAS sources
van der Walt D.J., Gaylard M.J., MacLeod G.C.
<Astron. Astrophys. Suppl. Ser. 110, 81 (1995)>
=1995A&AS..110...81V 1995A&AS..110...81V
ADC_Keywords: Infrared sources ; Masers
Keywords: masers - ISM: clouds - ISM: molecules - radio lines: ISM
Abstract:
We present the results of our second search for 6.7-GHz methanol
masers towards colour-selected IRAS sources. Five hundred and twenty
IRAS sources that meet the far-infrared colour criteria set by Wood &
Churchwell (1989ApJ...340..265W 1989ApJ...340..265W) for ultra-compact HII regions were
searched for 6.7-GHz methanol maser emission, to a sensitivity limit
of 5Jy. Thirty one new maser sources were detected. We also compare
the FIR colours of the newly detected maser sources with those
detected by Schutte et al. (1993MNRAS.261..783S 1993MNRAS.261..783S) and the IRAS
counterparts of sources that have both methanol and hydroxyl maser
emission. It was found that the average flux distribution of the newly
detected sources differs significantly from that of all other known
6.7-GHz methanol maser sources. It is argued that the differences may
be due either to intrinsic differences between the three groups of
sources or to interstellar extinction. An analysis of the relation
between the 6.7-GHz maser and IRAS flux densities shows that the maser
flux density is always less than the 100µm flux density while only
three sources have a maser flux density greater than the 60µm flux
density. Far-infrared pumping of the 6.7-GHz methanol masers is
therefore in principle viable although it was found that the apparent
maser efficiency will exceed 10 per cent for a significant number of
sources in the case of FIR pumping by photons between 50 and 100µm.
The overall detection rates on the IRAS [25-12] vs [60-12] two-colour
diagram are also presented. Possible new search strategies for masers
in colour-selected IRAS sources are discussed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 13 520 Source IRAS names
table2.dat 75 31 Parameters of detected 6.668-GHz A+-methanol masers
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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 A1 --- Note [abcd] Characteristics (1)
3- 13 A11 --- IRAS IRAS name (2)
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Note (1): Characteristics are:
a = Sources with no upper limits at 12, 25, 60 & 100µm
b = Sources with upper limit at 12 µm
c = Sources with upper limit at 100 µm
d = Sources with upper limits at 12 & 100 µm
Note (2): Misprint IRAS 06513-4316A for IRAS 16513-4316A, fixed at CDS
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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 name (Cat. II/125)
13- 14 I2 h RAh Right ascension (1950)
16- 17 I2 min RAm Right ascension (1950)
19- 22 F4.1 s RAs Right ascension (1950)
24 A1 --- DE- Declination sign
25- 26 I2 deg DEd Declination (1950)
28- 29 I2 arcmin DEm Declination (1950)
31- 32 I2 arcsec DEs Declination (1950)
34- 39 F6.2 deg GLON Galactic longitude
41- 45 F5.2 deg GLAT Galactic latitude
47- 50 I4 km/s Vmin Velocity range (lower value)
52- 55 I4 km/s Vmax Velocity range (upper value)
57- 61 F5.1 Jy Speak Peak flux density of 6.7GHz methanol line
63- 65 F3.1 Jy e_Speak rms uncertainty on Speak
67- 71 F5.1 Jy.km/s Ipeak Integrated peak flux density of methanol line
73- 75 F3.1 Jy.km/s e_Ipeak rms uncertainty on Ipeak
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History: Prepared via OCR at CDS.
* 31-Oct-1997: two errors in table1 detected and corrected.
(End) James Marcout, Patricia Bauer [CDS] 08-Apr-1997