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J/other/JApA/25.143  High galactic latitude HI absorption survey  (Mohan+, 2004)
A high galactic latitude HI 21 cm-line absorption survey using the GMRT.
I. Observations and spectra.
    Mohan R., Dwarakanath K.S., Srinivasan G.
   <J. Astrophys. Astron., 25, 143-183 (2004)>
   =2004JApA...25..143M
ADC_Keywords: Interstellar medium ; H I data ; Radio sources

Keywords: ISM: clouds, kinematics and dynamics - radio lines: ISM


Abstract:
    We have used the Giant Meterwave Radio Telescope (GMRT) to measure the
    Galactic HI 21-cm line absorption towards 102 extragalactic radio
    continuum sources, located at high (|b|>15°) Galactic latitudes.
    The Declination coverage of the present survey is DE~-45°. With a
    mean rms optical depth of ∼0.003, this is the most sensitive Galactic
    HI 21-cm line absorption survey to date. To supplement the absorption
    data, we have extracted the HI 21-cm line emission profiles towards
    these 102 lines of sight from the Leiden Dwingeloo Survey of Galactic
    neutral hydrogen. We have carried out a Gaussian fitting analysis to
    identify the discrete absorption and emission components in these
    profiles. In this paper, we present the spectra and the components. A
    subsequent paper will discuss the interpretation of these results.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
appena.dat        59      102   List of sources observed with the GMRT
appenc.dat       103      466  *Discrete HI features

Note on appenc.dat : List of the discrete HI features identified from
    the high latitude Galactic HI absorption survey using the GMRT and
    from the HI emission data along the respective lines of sight from 
    the Leiden-Dwingeloo survey (LDS) of Galactic.


See also:
    VIII/54 : Atlas of Galactic Neutral Hydrogen (Hartmann+, 1997)


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

   Bytes Format Units   Label     Explanations

   1-  9  A9    ---     Source    Source designation (JHHMM-DDd)
  11- 12  I2    h       RAh       Right ascension (J2000)
  14- 15  I2    min     RAm       Right ascension (J2000)
  17- 21  F5.2  s       RAs       Right ascension (J2000)
      23  A1    ---     DE-       Declination sign (J2000)
  24- 25  I2    deg     DEd       Declination (J2000)
  27- 28  I2    arcmin  DEm       Declination (J2000)
  30- 33  F4.1  arcsec  DEs       Declination (J2000)
  35- 40  F6.2  deg     GLON      Galactic longitude
  42- 47  F6.2  deg     GLAT      Galactic latitude
  49- 53  F5.3  ---     taurms    rms optical depth in the HI absorption spectra
  55- 59  F5.2  Jy      S1420MHz  Observed flux-density, at 1420.4MHz


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

   Bytes Format Units   Label     Explanations

   1-  9  A9    ---     Source    Name of the background source (1)
      12  A1    ---     l_tauHI   Limit flag on tauHI (for optical depth limit
                                    obtained from the HI absorption profiles
                                    along the respective directions
  13- 17  F5.3  ---     tauHI     ? HI absorption peak optical depth (GMRT)
                                    or HI absorption optical depth limit
                                    if l_tauHI = "<"
  19- 22  F4.3  ---     e_tauHI   ? rms uncertainty on tauHI
  24- 30  F7.3  km/s    VlsrA     ? HI absorption LSR velocity (GMRT) (2)
  32- 36  F5.3  km/s    e_VlsrA   ? rms uncertainty on VlsrA
  39- 43  F5.2  km/s    FWHMA     ? HI absorption mean FWHM (GMRT) (2)(3)
  44- 47  F4.2  km/s    e_FWHMA   ? rms uncertainty on FWHMA
  49- 54  F6.3  K       TB        ? HI emission brightness temperature (LDS)
  56- 60  F5.3  K       e_TB      ? rms uncertainty on TB
  62- 69  F8.3  km/s    VlsrE     ? HI emission LSR velocity (LDS) (4)
  71- 76  F6.3  km/s    e_VlsrE   ? rms uncertainty on VlsrE
  78- 83  F6.2  km/s    FWHME     ? HI emission mean FWHM (LDS) (4)
  85- 89  F5.2  km/s    e_FWHME   ? rms uncertainty on FWHME
      91  A1    ---     l_TS      Limit flag on TS
  92- 95  I4    K       TS        ? Spin temperature of the absorbing gas (5)
  97-103  A7    ---     Note      [No data] No data from LDS

Note (1): Background source, towards which the absorption was measured
          using the GMRT.
Note (2): Mean LSR velocity and the FWHM of discrete components identified
          using Gaussian fitting.
Note (3): The value of FWHM is deconvolved for a channel width of 3.26km/s.
          The unresolved lines are marked with a "-" .
Note (4): Value of deconvolved HI emission profile along the same line of
          sight, obtained from the Leiden-Dwingeloo Survey of Galactic
          neutral hydrogen (Hartman & Burton, 1995, LDS Cat. VIII/54)
Note (5): Spin temperature, calculated using the absorption and emission data.



History:
    From electronic version of the journal
(End)                                      Patricia Vannier [CDS]    12-Jun-2006