J/MNRAS/377/571 GLIMPSE 6.7GHz methanol masers non-detections (Ellingsen+, 2007)
A GLIMPSE-based search for 6.7-GHz methanol masers and the lifetime of their
spectral features.
Ellingsen S.P.
<Mon. Not. R. Astron. Soc., 377, 571-583 (2007)>
=2007MNRAS.377..571E 2007MNRAS.377..571E
ADC_Keywords: Masers ; Infrared sources ; Radial velocities
Keywords: masers - stars: formation - ISM: molecules - radio lines: ISM
Abstract:
The University of Tasmania Mt Pleasant 26-m and Ceduna 30-m radio
telescopes have been used to search for 6.7-GHz class II methanol
masers towards 200 GLIMPSE (The Galactic Legacy Infrared Mid-Plane
Survey Extraordinaire) sources. The target regions were selected on
the basis of their mid-infrared colours as being likely to be young
high-mass star formation regions and are either bright at 8.0µm, or
have extreme [3.6]-[4.5] colour. Methanol masers were detected towards
38 sites, nine of these being new detections. The prediction was that
approximately 20 new 6.7-GHz methanol masers would be detected within
3.5-arcmin of the target GLIMPSE sources, but this is the case for
only six of the new detections. A number of possible reasons for the
discrepancy between the predicted and actual number of new detections
have been investigated. It was not possible to draw any firm
conclusions as to the cause, but it may be because many of the target
sources are at an evolutionary phase prior to that associated with
6.7-GHz methanol masers. Through comparison of the spectra collected
as part of this search with those in the literature, the average
lifetime of individual 6.7-GHz methanol maser spectral features is
estimated to be around 150yr, much longer than is observed for 22-GHz
water masers.
Description:
The observations were made between 2005 July and 2005 December using
the University of Tasmania Mt Pleasant 26-m and Ceduna 30-m radio
telescopes.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 59 171 GLIMPSE sources searched for 6.7-GHz methanol
maser emission for which there was no detection
--------------------------------------------------------------------------------
See also:
http://www.astro.wisc.edu/glimpse/glimpsedata.html : GLIMPSE Home Page
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [GLMC]
6- 21 A16 --- GLIMPSE GLIMPSE PSC name, GLLL.llll+B.bbb
23 A1 --- Cat [AB] Category of selection (1)
25- 26 I2 h RAh Right ascension (J2000)
28- 29 I2 min RAm Right ascension (J2000)
31- 34 F4.1 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 44 I2 arcsec DEs Declination (J2000)
46- 48 F3.1 Jy rms rms for the spectrum after box car smoothing
to a velocity resolution of 0.22km/s
50- 53 I4 km/s Vel1 Velocity range (lower limit)
55 A1 --- --- [-]
57- 59 I3 km/s Vel2 Velocity range (upper limit)
--------------------------------------------------------------------------------
Note (1): Category as follows:
A = object selected on the basis of having a large [3.6]-[4.5] excess
B = object selected on the basis of high intensity in the 8.0um band
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 12-Oct-2007