ACDS V10.0 - Detailed Description of VIII/62

ACDS V10.0 - Sun Jan 19 03:01:27 CET 2025

| # Detailed Description of VIII/62 : The Westerbork Northern Sky Survey (Leiden, 1998) |

Note : this is the description file of the original catalog. This HTML page corresponds well to the original description, but some minor changes in the format may have been introduced in the FITS output files in order to allow for arithmetic operations on quantities such as coordinates and times. h:m:s and d:m:s units are normally converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the units; the value given in the HTML files supersedes the value indicated in the ReadMe file for this catalogue.

    VIII/62             The Westerbork Northern Sky Survey      (Leiden, 1998)
    ================================================================================
    Westerbork Northern Sky Survey (WENSS)
       de Bruyn G., Miley G., Rengelink R., Tang Y., Bremer M., Rottgering H.,
       Raimond R., Bremer M., Fullagar D.
      <WENSS Collaboration NFRA/ASTRON and Leiden Observatory (1998)>
    ================================================================================
    ADC_Keywords: Radio sources ; Surveys

    Description:
        The Westerbork Northern Sky Survey (WENSS) is a low-frequency radio
        survey that covers the whole sky north of 30° at a wavelength of
        92cm (330MHz) to a limiting flux density of approximately 18 mJy
        (5{sigma}). This survey has a resolution of 54"x54" cosec(delta) and a
        positional accuracy for strong sources of 1.5".

        The WENSS project is a collaboration between the Netherlands
        Foundation for Research in Astronomy (NFRA/ASTRON) and the
        Leiden Observatory.

    Introduction to the WENSS:
        The Westerbork Northern Sky Survey (WENSS) is a radio survey made with
        the WSRT at wavelengths 92 and 49 cm. At 92 cm the entire sky above
        declination 30° is covered. The other wavelength regime does
        not cover the whole sky, but only 30-50 percent, due to the amount of
        telescope time that is needed to do this. Using a synthesis array like
        the WSRT means that we get a better resolution than single dish
        observations, but also has the disadvantage of a smaller field of
        view, unless we find a way of dealing with wide field imaging. The
        solution for this problem is mosaicing. Instead of making one
        observation of a large field we make a lot of snapshots of different
        fields and bind them together with the help of special build software.
        A typical mosaic contains 80 pointing centres. Each pointing centre is
        sampled during 20 seconds and then the telescope moves to another
        centre. This takes about 10 seconds. After 40 minutes all fields are
        scanned and the procedure starts again. This means that in a 12 hour
        observation each field is scanned 18 times. To move grating rings of
        the map 6 different baseline settings are used, so 1 mosaic data block
        involves 72 hours of observational data. Each pointing centre is
        located at half half-power maximum beamwidth in order to get a smooth
        sampling grid of the data. The noise background is uniform up to 5
        percent. At 92 cm (declination 30°) a mosaic block is about 10
        by 14° large.

        The final product that the WENSS survey produces contain 6x6°
        frames taken from the mosaic blocks. They are centered on the new POSS
        plate positions (5° grid). The limiting flux density will be about
        15 mJy (5 sigma) at both wavelengths. As a result the final catalogue
        will consist of 300,000 sources at 92 cm and 60,000 at 49 cm. The
        positional accuracy will be superior to all other all sky surveys (5"
        for the faint sources to better than 1" for the stronger sources). A
        large number of sources will have sufficient accurate positions to
        allow optical identification using a digitized version of the Palomar
        Sky Survey made with the APM at Cambridge. Final maps will be made at
        different resolutions in order to make accurate spectral index
        measurements. At each wavelength we will make high, medium and low
        resolution maps (1', 2.5' and 4' resolution at 92 cm and 0.5', 1' and
        2.5' resolution at 49 cm). Maps will be made with all Stokes
        parameters (I, Q, U and V). This means that source information will be
        available both on spectral type and polarization characteristics. This
        is important for using the catalogue as a database for finding sources
        based on well known selection criteria, such as steep spectra for high
        redshift radio galaxies.

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × main.dat         114   211234   WENSS main catalogue (28 to 76°)
    × polar.dat        114    18186   WENSS polar catalogue (sources above 72°)

    See also:
        http://www.strw.leidenuniv.nl/wenss/ : the WENSS Home Page
        ftp://vliet.strw.leidenuniv.nl/pub/wenss/HIGHRES/ : maps in FITS format
        J/A+AS/124/259 : The Westerbork Northern Sky Survey I. (Rengelink+ 1997)

    Byte-by-byte Description of file:  main.dat  polar.dat

       Bytes Format Units   Label     Explanations

       1-  2  A2    ---     ---       [WN] Survey name
       3- 15  A13   ---     Name     *Designation of the source
          16  A1    ---     f_Name   *[abmp] Several objects share the same name
      18- 19  I2    h       RA1950h   Right Ascension B1950 (hours)
      21- 22  I2    min     RA1950m   Right Ascension B1950 (minutes)
      24- 28  F5.2  s       RA1950s   Right Ascension B1950 (seconds)
          30  A1    ---     DE1950-   Declination B1950 (sign)
      31- 32  I2    deg     DE1950d   Declination B1950 (degrees)
      34- 35  I2    arcmin  DE1950m   Declination B1950 (minutes)
      37- 40  F4.1  arcsec  DE1950s   Declination B1950 (seconds)
      43- 44  I2    h       RAh       Right Ascension J2000 (hours)
      46- 47  I2    min     RAm       Right Ascension J2000 (minutes)
      49- 53  F5.2  s       RAs       Right Ascension J2000 (seconds)
          55  A1    ---     DE-       Declination J2000 (sign)
      56- 57  I2    deg     DEd       Declination J2000 (degrees)
      59- 60  I2    arcmin  DEm       Declination J2000 (minutes)
      62- 65  F4.1  arcsec  DEs       Declination J2000 (seconds)
          68  A1    ---     flg1     *[SMEC] source type flag
          70  A1    ---     flg2     *[*] problems in fitting the source
      73- 78  I6    mJy     Speak    *Peak flux density at 330MHz in mJy/beam
      80- 86  I7    mJy     Sint     *Integrated flux density 330MHz in mJy
      88- 91  I4    arcsec  MajAxis  *Major axis
      93- 95  I3    arcsec  MinAxis  *Minor axis
      97- 99  I3    deg     PA       *Position angle (North to East)
     101-104  F4.1  mJy     Nse       Local rms-noise level in mJy/beam
     106-114  A9    ---     Frame     Frame from which the source was obtained

    Note on Name, f_Name:
        The name has a format 'Bhhmm.m+ddmmA', where 'B' indicates a name based
        on B1950 coordinates, followed by the truncated position to 0.1min in
        right ascension and 1 arcmin in declination, followed by a letter
        A,B,C,D for components of the multi-component sources.

        There are 748 names which are assigned to more than one source; these
        names are flagged "a", "b", "m" or "p" in the f_Name column:
         a,b  when the same name exists in the same file (there are two
              identical names in main.dat or polar.dat)
         m,p  when the same name exists in the other file (there are two
              identical names, one in main.dat, and the other one in polar.dat)
    Note on flg1: this flag indicates the source type as:
         S = Single component source
         M = Multicomponent source
         C = Component of a multicomponent source
         E = Extended source (more than four components)
    Note on flg2: warning flag indicating problems in fitting the source.
         Source parameters were then obtained using 'aperture' integration.
    Note on Speak, Sint:
         The frequency is 325MHz in the main part, and 352MHz in the polar part.
    Note on MajAxis, MinAxis, PA: sources that are probably resolved.
        Non-null numbers indicate that the flux density ratio Sint/Speak
        exceeds a signal-to-noise dependent threshold. This threshold is the
        flux ratio Sint/Speak that is exceeded by less than 5% of the
        unresolved sources. These parameters have not been deconvolved.

    Project Team:
      Project scientists:  A.G. de Bruyn, G.K. Miley
      Project manager:  E. Raimond
      Research assistants:  M.A.R. Bremer (Leiden), Y. Tang (Dwingeloo)
      Software design/coding (NEWSTAR): W.N. Brouw
      Software design/coding (Catalogue building / user interfaces): M.A.R. Bremer
      WSRT on-line assistance: R. Braun, H. van Someren-Greve
      Dwingeloo off-line processing: G. van Diepen, J.E. Noordam

        Several AIO's / OIO's (Ph.D. students) will work with the catalogue,
        each with their own sources of interest (e.g. milli-second pulsars,
        high redshift galaxies, GHZ peakers).

    Data Rights/Acknowledgements:
        Anyone using data from the WENSS database in publications is asked to
        acknowledge this. Comments or questions about the survey can be
        addressed to any of the people mentioned below or to the general
        wenss.people@strw.leidenuniv.nl account at Leiden.

    History:
      * 10-Feb-2000: Prepared at ADC.
      * 21-Oct-2003: 19 sources from main.dat had a blank embedded in the
        name, just following the "WNB" in the Name column; this blank
        was removed at CDS.
      * 14-May-2004: the column f_Name was installed to distinguish the
        sources sharing an identical name.
    ================================================================================
    (End)  Gail L. Schneider [SSDOO/ADC],  Francois Ochsenbein [CDS]     10-Feb-2000