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J/MNRAS/291/261     Methanol maser of IRAS-selected sources (Walsh+ 1997)
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)
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:

       FileName      Lrecl  Records   Explanations

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


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

   Bytes Format Units   Label     Explanations

   1- 11  A11   ---     IRAS      IRAS PSC name (Cat. II/125)


Byte-by-byte Description of file: table2.dat

   Bytes Format Units     Label     Explanations

   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)

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)


Acknowledgements: Andrew Walsh 

(End)                                          Patricia Bauer [CDS]  14-Nov-1997