ACDS V10.0 - Detailed Description of J/MNRAS/278/1025

ACDS V10.0 - Mon Jan 20 03:41:26 CET 2025

| # Detailed Description of J/MNRAS/278/1025 : The APM Bright Galaxy Catalogue (Loveday 1996) |

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.

    J/MNRAS/278/1025     The APM Bright Galaxy Catalogue  (Loveday 1996)
    ================================================================================
    The APM Bright Galaxy Catalogue
        Loveday J.
       <Mon. Not. R. Astron. Soc. 278, 1025 (1996)>
       =1996MNRAS.278.1025L
    ================================================================================
    ADC_Keywords: Galaxy catalogs ; Photometry

    Abstract:
        The APM Bright Galaxy Catalogue lists positions, magnitudes, shapes
        and morphological types for 14,681 galaxies brighter than b(J)
        magnitude 16.44 over a 4,180 square degree area of the southern sky.
        Galaxy and stellar images have been located from glass copy plates of
        the United Kingdom Schmidt Telescope (UKST) IIIaJ sky survey using the
        Automated Photographic Measuring (APM) facility in Cambridge, England.
        The majority of stellar images are rejected by the regularity of their
        image surface brightness profiles. Remaining images are inspected by
        eye on film copies of the survey material and classed as stellar,
        multiple stellar, galaxy, merger or noise. Galaxies are further
        classified as elliptical, lenticular, spiral, irregular or uncertain.
        The 180 survey fields are put onto a uniform photometric system by
        comparing the magnitudes of galaxies in the overlap regions between
        neighbouring plates. The magnitude zero-point, photometric uniformity
        and photographic saturation are checked with CCD photometry. Finally,
        the completeness and reliability of the catalogue is assessed using
        various internal tests and by comparing with several independently
        constructed galaxy catalogues.

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × galaxy.dat        64    14681   Galaxies in APM-BGC
    × fields.dat        23      180   Field centres
    × holes.dat         75     1456   Holes drilled around big bright objects

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

       Bytes Format Units    Label     Explanations

       1- 11  A11   ---      ID        Galaxy name (1)
          12  A1    ---      m_ID      [AB] Multiplicty index on ID (2)
      14- 15  I2    h        RAh       Right Ascension 1950 (hours)
      17- 18  I2    min      RAm       Right Ascension 1950 (minutes)
      20- 24  F5.2  s        RAs       Right Ascension 1950 (seconds)
          27  A1    ---      DE-       Declination 1950 (sign)
      28- 29  I2    deg      DEd       [17,72] Declination 1950 (degrees)
      31- 32  I2    arcmin   DEm       Declination 1950 (arcminutes)
      34- 37  F4.1  arcsec   DEs       Declination 1950 (arcseconds)
      40- 44  F5.2  mag      Bj        Bj magnitude
      47- 49  I3    arcsec   MajDiam   Major diameter
      52- 54  I3    arcsec   MinDiam   Minor diameter
      57- 59  I3    deg      PA        [0,360[ Position angle (degrees) (3)
      63- 64  I2    ---      MType     Morphological type (4)

    Note (1):
      Each galaxy name is composed of the survey field number and the x, y
      position of the galaxy on the plate---this should ease location of any
      particular galaxy on the plate material.  The first 3 digits are the
      SERC field number.  The second set of digits are the x-position in
      millimetres from the centre of the plate (actually the APM scan
      centre).  These are preceded by a `+' sign for galaxies to the right
      (west) of the plate centre or by a `-' sign for galaxies to the left
      (east) of centre.  The final 3 digits are the y position, again in
      mm from the plate centre.  A preceding `-' indicates galaxies above
      (north) of the plate centre, `+' indicates galaxies below (south) of
      the centre.
    Note (2): Some galaxies having the same name, a letter (A or B) was added
               on 20-Jan-2004 by the CDS team
    Note (3):
      PA is measured clockwise from south-north line.
    Note (4):
      The morphological type is given by mod(Mtype,10)
      1 = Elliptical
      2 = Lenticular
      3 = Spiral
      4 = Irr/Pec
      5 = Uncertain
      8 = Merged with star
      9 = Multile galaxy
      Galaxies from the ESO catalogue have 10 added.

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

       Bytes Format Units   Label       Explanations

       1-  3  I3    ---     Field       [53,605] SERC field number
       5- 10  F6.2  deg     RAdeg       RA  of field centre 1950 (degrees) (1)
      12- 17  F6.2  deg     DEdeg       Dec of field centre 1950 (degrees) (1)
      19- 23  F5.3  deg     RAextent    RA extent of field (degrees) (1)

    Note (1):
        This table lists SERC field centres in 1950 decimal degrees. The
        column labeled RAextent gives the half-size of the Right Ascension of
        the field in degrees. The DEextent is 2.5 degrees for every field.
        This list of fields may be used for example to generate a random
        catalogue with the same boundaries as the survey data as follows:

        A point with coordinates (RAp, DEp) is inside a field with coordinates
        (RAf, DEf) if (abs(RAp - RAf) < RAextent) and (abs(DEp-DEf) < DEextent).

        An additional test should be made to allow for the extra overlap
        between fields at RA = 0. If RAf is not zero then abs(RAp) must be
        greater than RAextent.

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

       Bytes Format Units   Label       Explanations

       1-  3  I3    ---     Field       [53,605] SERC field number
       5- 15  F11.7 deg     HOLX1       RA  of 1st corner of hole (degrees) (1)
      17- 27  F11.7 deg     HOLY1       Dec of 1st corner of hole (degrees) (1)
      29- 39  F11.7 deg     HOLX2       RA  of 2nd corner of hole (degrees) (1)
      41- 51  F11.7 deg     HOLY2       Dec of 2nd corner of hole (degrees) (1)
      53- 63  F11.7 deg     HOLX3       RA  of 3rd corner of hole (degrees) (1)
      65- 75  F11.7 deg     HOLY3       Dec of 3rd corner of hole (degrees) (1)

    Note (1):
      This table lists the coordinates of parallelogram shaped holes drilled
      out around big bright objects in the survey.  The following FORTRAN code
      will test if a point with coordinates (xr,yr) lies in a hole:

    c
    c *** Set drilled =  .true. if point (xr,yr) lies in a given hole
    c
    c     Method: Express displacement vector to (xr,yr) in terms of basis
    c     vectors of parallelogram
    c
    c       Vr = a1*V1 + a2*V2
    c       -       -       -
    c
    c     Then (xr,yr) is drilled if  0 <= a1,a2 <= 1
    c
          drilled = .false.
          dx = xr - HOLX1
          dy = yr - HOLY1
          dx1 = HOLX2 - HOLX1
          dy1 = HOLY2 - HOLY1
          dx2 = HOLX3 - HOLX1
          dy2 = HOLY3 - HOLY1

          if (abs(dx2).gt.0) then
             a1 = (dx*dy2 - dy*dx2)/(dx1*dy2 - dy1*dx2)
             a2 = (dx - a1*dx1)/dx2
             if (0.le.a1.and.a1.le.1.and.0.le.a2.and.a2.le.1) drilled = .true.
          endif

    History:
      * 21-Feb-1996: Original version
      * 20-Jan-2004: In file "galaxy.dat, some galaxies having the same name,
           a letter (A or B) was added by the CDS team.
      * 01-Jul-2009: Two corrections in galaxy names ('B' added for duplicated
           names) for 118-016-026 and 118-017+045.
    ================================================================================
    (End)       Jon Loveday [Fermilab]                                   21-Feb-1996