J/ApJ/587/714    H_2_CO and H{alpha} observations of UC HII      (Watson+, 2003)
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Resolution of distance ambiguities of inner galaxy massive star formation
regions. I.
    Watson C., Araya E., Sewilo M., Churchwell E., Hofner P., Kurtz S.
   <Astrophys. J., 587, 714-726 (2003)>
   =2003ApJ...587..714W
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ADC_Keywords: H II regions ; Radio lines
Keywords: Galaxy: disk - radio lines: general - stars: formation

Abstract:
    Fifty-four ultracompact (UC) HII regions in the GLIMPSE survey region
    (|b|<1{deg} and 30{deg}<l<70{deg}) were observed in H_2_CO and
    H110{alpha} using the 305 m Arecibo telescope. By analyzing H_2_CO
    absorption against the UC H II region continuum emission, we resolve
    the distance ambiguity toward 44 sources. This determination is
    critical to measure global physical properties of UC H II regions
    (e.g., luminosity, size, mass) and properties of the Galaxy (e.g.,
    spiral structure, abundance gradients). We find that the distribution
    of UC H II regions in this survey is consistent with a ``local spur'',
    the Perseus, Sagittarius, and Scutum arms as delineated by Taylor &
    Cordes. However, departures from model velocities produce distance
    uncertainties only slightly smaller than the proposed arm separations.

Description:
    The observations were made between 2002 July 24 and 29 with the 305m
    Arecibo Telescope. The 1_10_-1_11_ transition of interstellar
    formaldehyde (H2CO, {nu}0=4829.6594MHz for F=2-2) was observed in
    absorption against UC H II regions. Simultaneously, the H110{alpha}
    ({nu}0=4874.1570MHz) radio recombination line was observed to establish
    kinematic distances.

File Summary:
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 FileName    Lrecl  Records   Explanations
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ReadMe          80        .   This file
table1.dat      50       54   Observed sources
table2.dat      65       54   H110{alpha} line (4874.16MHz) 
                              and continuum parameters
table3.dat      76      138   Formaldehyde (H_2_CO, 4829.66MHz) line parameters
table4.dat      75       93   Kinematic parameters
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See also:
          II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
 J/A+AS/115/81   : A CS(2-1) survey of UC HII regions (Bronfman+, 1996)
 J/A+AS/120/283  : Water maser features in UC HII regions (Hofner+ 1996)
 J/A+A/336/339   : VLA observations of ultracompact HII regions (Molinari+ 1998)
 J/MNRAS/301/640 : Ultracompact H II regions studies. II. (Walsh+, 1998)
 J/ApJS/138/63   : H2CO and Halpha observations of UC HII (Araya+, 2002)
 J/ApJS/155/123  : JHKs photometry of ultracompact HII regions (Alvarez+, 2004)
 J/A+A/417/615   : Maser and outflows in UC HII region (Codella+, 2004)
 J/A+A/453/1003  : SCUBA ultracompact HII regions (Thompson+, 2006)
 J/ApJS/91/659   : Ultracompact HII regions radio images (Kurtz+ 1994)
 J/MNRAS/420/1656 : RMS compact HII regions distances (Urquhart+, 2012)

Byte-by-byte Description of file: table1.dat
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   Bytes Format Units   Label     Explanations
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   1- 11  A11   ---     Name      Source name, GLL.ll+D.dd
  13- 14  I2    h       RAh       Right ascension (B1950)
  16- 17  I2    min     RAm       Right ascension (B1950)
  19- 22  F4.1  s       RAs       Right ascension (B1950)
      24  A1    ---     DE-       Declination sign (B1950)
  25- 26  I2    deg     DEd       Declination (B1950)
  28- 29  I2    arcmin  DEm       Declination (B1950)
  31- 32  I2    arcsec  DEs       Declination (B1950)
  34- 44  A11   ---     IRAS      IRAS name
  46- 50  F5.1  hJy     S100      IRAS 100{mu}m flux density
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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   ---       Name      Source name
      13  A1    ---     f_Name      [a] SNR (1)
  15- 21  F7.1  mJy       Sc        Continuum flux density
  23- 25  F3.1  mJy     e_Sc        The 1{sigma} error in Sc
  27- 31  F5.1  mJy       SH110a    ? H110{alpha} flux density
  33- 35  F3.1  mJy     e_SH110a    ? The 1{sigma} error in SH110a
  37- 41  F5.1  km/s      VLSR      ? The Local Standard of Rest velocity
  43- 45  F3.1  km/s    e_VLSR      ? The 1{sigma} error in VLSR
  47- 50  F4.1  km/s      FWHM      ? The Full-Width at Half-Maximum
  52- 54  F3.1  km/s    e_FWHM      ? The 1{sigma} error in FWHM
  56- 60  I5   mJy.km/s   Sint      ? The integrated H110{alpha} line flux
      62  A1    ---     l_Sint      Limit flag on Sint error (e_Sint)
  63- 65  I3   mJy.km/s e_Sint      ? The 1{sigma} error on Sint
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Note (1): a = This source is a supernova remnant
     (see Brogan & Troland, 2001ApJ...550..799B)
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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- 11  A11   ---       Name      Source name (1)
   13-15  A3    ---       CName     Intervening cloud identification (1)
  17- 25  F9.3  mJy       Sc        ? Continuum flux density
  27- 31  F5.3  mJy     e_Sc        ? The 1{sigma} error in Sc
  33- 39  F7.1  mJy       SH2CO     ? H_2_CO flux density
  41- 43  F3.1  mJy     e_SH2CO     ? The 1{sigma} error in SH2CO
  45- 49  F5.1  km/s      VLSR      ? The Local Standard of Rest velocity
      51  A1    ---     l_VLSR      Limit flag on the VLSR error
  52- 54  F3.1  km/s    e_VLSR      ? The 1{sigma} error in VLSR
  56- 59  F4.1  km/s      FWHM      ? The Full-Width at Half-Maximum
      61  A1    ---     l_FWHM      Limit flag on the FWHM error
  62- 64  F3.1  km/s    e_FWHM      ? The 1{sigma} error in FWHM
  66- 71  I6   mJy.km/s   Sint      ? The integrated H_2_CO line flux
      73  A1    ---     l_Sint      Limit flag on the Sint error
  74- 76  I3   mJy.km/s e_Sint      ? The 1{sigma} error on Sint
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Note (1): Indicates the direction of the H_2_CO cloud, but we do not imply
     an association between the H_2_CO cloud and the UC HII region.
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Byte-by-byte Description of file: table4.dat
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   Bytes Format Units     Label     Explanations
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   1- 11  A11   ---       Name      Source name
      13  A1    ---     f_Name      [a] Note on near/far distance (1)
  15- 17  A3    ---       CName     Intervening cloud identification
  19- 23  F5.1  km/s      VLSR      The Local Standard of Rest velocity
  25- 27  F3.1  km/s    e_VLSR      The 1{sigma} error in VLSR
  29- 32  F4.1  kpc       DNear     ? Inner Galaxy circular orbit near distance
  34- 37  F4.1  kpc       DFar      ? Inner Galaxy circular orbit far distance
  39- 42  F4.1  kpc       VTP       Distance derived to tangent point
  44- 46  F3.1  kpc       DTP       Resolved Distance
  48- 53  F6.3  kpc       DLSR      ? Distance derived from VLSR
  55- 57  F3.1  kpc     E_DLSR      ? Upper 1{sigma} error in DLSR
  59- 61  F3.1  kpc     e_DLSR      ? Lower 1{sigma} error in DLSR
  63- 65  I3    pc        z         ? Galactic scale height
  67- 70  F4.2  kpc       DGC       Distance from the Galactic center
  72- 75  A4    ---       Near/Far  Comment on the source distance (2)
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Note (1): a = Araya et al. (2002ApJS..138...63A) report the near kinematic
   distance to this source.  The data presented here has a better signal to
   noise than the Araya et al. spectra. Our observations revealed a weak H_2_CO
   absorption not detected by Araya et al. which imply the FAR kinematic
   distance.
Note (2): "Near" or "Far" distance estimation, or ambiguous:
  b = This source has a velocity higher then the tangent velocity. We
      locate this source at the tangent point, but this position should be
      taken with caution since its velocity is not strictly predicted in
      our rotation model.
  c = This source has a velocity within 10km/s of the tangent velocity.
      Because we are unable to strongly distinguish between the near and
      far distance, we do not give a classification or distance.
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History:
    From electronic version of the journal

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(End)                  Greg Schwarz [AAS], Patricia Vannier [CDS]    19-Feb-2014