ACDS V10.0 - Detailed Description of VII/250

ACDS V10.0 - Sun Jan 19 06:47:01 CET 2025

| # Detailed Description of VII/250 : The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003) |

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.

    VII/250       The 2dF Galaxy Redshift Survey  (2dFGRS)  (2dFGRS Team, 1998-2003)
    ================================================================================
    The 2dF Galaxy Redshift Survey (2dFGRS)
        Colless M., Dalton G., Maddox S., Sutherland W., Norberg P., Cole S.,
        Bland-Hawthorn J., Bridges T., Cannon R., Collins C., Couch W., Cross N.,
        Deeley K., de Propris R., Driver S.P., Efstathiou G., Ellis R.S.,
        Frenk C.S., Glazebrook K., Jackson C., Lahav O., Lewis I., Lumsden S.,
        Madgwick D., Peacock J.A., Peterson B.A., Price I., Seaborne M., Taylor K.
       <Mon. Not. R. Astron. Soc. 328, 1039 (2001)>
       =2001MNRAS.328.1039C
    ================================================================================
    ADC_Keywords: Surveys ; Galaxy catalogs ; Redshifts ; Galaxies, photometry

    Keywords: Surveys, galaxies: clusters: general ;
              Galaxies: distances and redshifts ; Cosmology: observations ;
              Large-scale structure of Universe

    Description:
        The 2dF Galaxy Redshift Survey (2dFGRS) is a major spectroscopic
        survey taking full advantage of the unique capabilities of the 2dF
        facility built by the Anglo-Australian Observatory. The 2dFGRS is
        integrated with the 2dF QSO survey (2QZ, Cat. VII/241).

        The 2dFGRS obtained spectra for 245591 objects, mainly galaxies,
        brighter than a nominal extinction-corrected magnitude limit of
        bJ=19.45. Reliable (quality>=3) redshifts were obtained for 221414
        galaxies. The galaxies cover an area of approximately 1500 square
        degrees selected from the extended APM Galaxy Survey in three regions:
        a North Galactic Pole (NGP) strip, a South Galactic Pole (SGP) strip,
        and random fields scattered around the SGP strip.

        Redshifts are measured from spectra covering 3600-8000 Angstroms at a
        two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel.
        All redshift identifications are visually checked and assigned a
        quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4%
        reliable and have an rms uncertainty of 85 km/s. The overall redshift
        completeness for Q>=3 redshifts is 91.8% but this varies with
        magnitude from 99% for the brightest galaxies to 90% for objects at
        the survey limit.

        The 2dFGRS data base is available on the World Wide Web at
        http://www.mso.anu.edu.au/2dFGRS/.

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × 2dfgrs.dat       188   245591   Best observations of 2dFGRS
    × spectra.dat       99   269937   Observed spectra
    × parent.dat       142   407834   Details of source observations
    × ngp.dat          209   135879   Photometric catalog in North Galactic Pole region
    × sgp.dat          209   190824   Photometric catalog in South Galactic Pole region
    × ran.dat          209    55620   Photometric catalog in random regions

    See also:
       http://www.mso.anu.edu.au/2dFGRS/ : The 2dF Galaxy Redshift Survey Home Page
       VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)

    Byte-by-byte Description of file:  2dfgrs.dat

       Bytes Format Units   Label    Explanations

       1-  6  I06   ---     SeqNum   2dFGRS serial number (SEQNUM)
           8  I1    ---    o_SeqNum  [1,6] Number of spectra obtained
      10- 19  A10   ---     Name     2dFGRS name (NAME)
      21- 23  I03   ---     UKST     UKST plate number (IFIELD)
      25- 26  I2    h      RA1950.h  Right ascension (B1950, hours)
      28- 29  I2    min    RA1950.m  Right ascension (B1950, minutes)
      31- 35  F5.2  s      RA1950.s  [0,60.] Right ascension (B1950, seconds)
          37  A1    ---    DE1950.-  Declination sign (B1950)
      38- 39  I2    deg    DE1950.d  Declination (B1950, degrees)
      41- 42  I2    arcmin DE1950.m  Declination (B1950, minutes)
      44- 47  F4.1  arcsec DE1950.s  [0,60.] Declination (B1950, seconds)
      49- 50  I2    h       RAh      Right ascension (J2000, hours)
      52- 53  I2    min     RAm      Right ascension (J2000, minutes)
      55- 59  F5.2  s       RAs      [0,60.] Right ascension (J2000)
          61  A1    ---     DE-      Declination sign (J2000, seconds)
      62- 63  I2    deg     DEd      Declination (J2000, degrees)
      65- 66  I2    arcmin  DEm      Declination (J2000, minutes)
      68- 71  F4.1  arcsec  DEs      [0,60.] Declination (J2000, seconds)
      73- 78  F6.3  mag     Bjmag    Final bj magnitude (BJG) (1)
      80- 85  F6.3  mag     Bjsel    Final bj magnitude corrected from
                                           extinction (BJSEL) (G2)
      87- 92  F6.3  mag     Bjmag.o  Original bj magnitude (BJG_OLD) (1)
      94- 99  F6.3  mag     Bjsel.o  Original bj magnitude corrected from
                                           extinction (BJSELOLD)
     102-106  F5.3  mag     Gext     Galactic extinction value (GALEXT)
     108-113  F6.3  mag     Bjmag.S  ?=0 SuperCosmos bj magnitude (SB_BJ) (1)
     115-120  F6.3  mag     Rmag.S   ?=0 SuperCosmos R magnitude  (SR_R) (1)
     122-128  F7.4  ---     z.obs    ?=-9 Best redshift (observed) (Z) (2)
     130-136  F7.4  ---     z        ?=-9 Best redshift (heliocentric) (Z_HELIO) (2)
     138-142  A5    ---     ObsRun   Observation run of best spectrum (OBSRUN)
         144  I1    ---     q_z      [1,5] Redshift quality for best spectrum
                                          (reliable redshifts have quality>=3) (2)
         146  I1    ---     n_z      Redshift type (abs=1, emi=2, man=3) (ABEMMA)
     148-154  F7.4  ---     z.abs    ?=-9.999 Cross-correlation redshift (Z_ABS) (2)
         156  I1    ---     T        Cross-correlation template (KBESTR) (2)
     158-162  F5.2  ---     Rx       ?=-9.99 Cross-correlation R value (R_CRCOR) (2)
     164-170  F7.4  ---     z.em     ?=-9.999 Emission redshift (Z_EMI) (2)
         172  I1    ---     o_z.em   Number of emission lines for Z_EMI (NMBEST) (2)
     175-179  F5.1  ---     SNR      Median signal to noise ratio per pixel (2)
     181-188  F8.4  ---     eta      ?=-99.9 Eta spectral type parameter
                                             from best spectrum (ETA_TYPE) (G1)

    Note (1): without extinction correction.

    Note (2): from best spectrum.
         When there is more than one 2dFGRS spectrum for a source, the best
         spectrum is the one with the highest redshift quality code; if there
         is more than one spectrum of this quality, then the spectrum with the
         latest date of observation is used. The other spectra are summarized
         in the file spectra.dat

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

       Bytes Format Units   Label    Explanations

       1-  6  I06   ---     SeqNum   Database serial number (SEQNUM)
       8- 17  A10   ---     Name     2dFGRS name (NAME)
      19- 28  A10   "Y:M:D" ObsDate  UT date of observation (UTDATE)
      30- 34  A5    ---     ObsRun   Observation run  (OBSRUN)
      36- 42  F7.4  ---     z.obs    ?=-9.99 Redshift (observed) (Z)
      44- 50  F7.4  ---     z        ?=-9.99 Redshift (heliocentric) (Z_HELIO)
          52  I1    ---     q_z      [1,5] Redshift quality parameter (QUALITY)
          54  I1    ---     n_z      Redshift type (abs=1, emi=2, man=3) (ABEMMA)
      56- 62  F7.4  ---     z.abs    ?=-9.999 Cross-correlation redshift (Z_ABS)
          64  I1    ---     T        Cross-correlation template (KBESTR)
      66- 70  F5.2  ---     Rx       ?=-9.99 Cross-correlation R value (R_CRCOR)
      71- 72  A2    ---     ---      [00]
      74- 80  F7.4  ---     z.em     ?=-9.999 ?=-9.99 Emission redshift (Z_EMI)
          82  I1    ---     o_z.em   Number of emission lines (NMBEST)
      85- 89  F5.1  ---     SNR      Median signal to noise ratio per pixel (SNR)
      91- 98  F8.4  ---     eta      ?=-99.9 spectral type parameter (G1)
          99  A1    ---     ---      [0]

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

       Bytes Format Units   Label    Explanations

       5- 10  I06   ---     SeqNum   Assigned sequence number to this object;
                                     determines the FITS filename (SEQNUM.fits)
      13- 21  F9.6  rad     RArad    Right ascension (B1950), radians
      23- 31  F9.6  rad     DErad    Declination (B1950), radians
      33- 38  F6.3  mag     Bjsel    (BJSEL) Final bj magnitude (1)
      40- 47  F8.5  ---     z.obs    ?=-9.99 Best redshift (observed)
      49- 56  F8.5  ---     z        ?=-9.99 Best redshift (heliocentric)
      58- 63  F6.3  mag     bjlim    ?=-1 2dFGRS bj magnitude limit of this area (2)
      65- 67  I3    ---     q_z      [1,5]?=-99 Redshift quality parameter
                                     (reliable redshifts have quality>=3)
      71- 76  F6.3  mag     Bjmag    Final bj without extinction correction (BJG)
      78- 82  F5.2  mag     Bj.ori   Original bj magnitude with extinction
                                      correction (BJSELOLD)
      84- 88  F5.2  mag     Bj.old   Original bj magnitude without extinction
                                       correction (BJG_OLD)
      90- 92  I03   ---     UKST     UKST plate number (IFIELD)
      94- 96  I3    ---     obsfld   ?=-99 Observed field number (OBSFLD(4:6))
      99-104  I6   "yyMMDD" GRSdate  ?=000000 Observation date (GRSDATE)
     107-114  F8.3  ---     eta      ?=-999 Spectral type parameter (ETA_TYPE) (G1)
     117-119  I3    ---     Plate    [0,1]?=-99 2dF plate (0 or 1) (PLATE)
     122-126  F5.3  ---     e        Eccentricity of the image (ECCENT)
     129-131  I3    deg     ora      [0,180[ Orientation angle E-(N)-W (ORIENT)
     134-135  I2    ---     jon      ?=-1 Eyeball classification (JON) (G3)
     138-142  I5    pix     area     Isophotal area in pixels (AREA)

    Note (1): Final bj magnitude with extinction correction (i.e.  with
         corrections for isophote, field-effects and plate-matching, then
         calibrated to total mags with  saturation correction, and then
         extinction corrected)
    Note (2): value -1.000 for sources not included in the survey sample

    Byte-by-byte Description of file:  ngp.dat  sgp.dat  ran.dat

       Bytes Format Units  Label   Explanations

       1-  6  I06   ---    SeqNum  Database serial number (SEQNUM)
       9- 10  I2    h      RAh     Right Ascension B1950 (hours)
      12- 13  I2    min    RAm     Right Ascension B1950 (minutes)
      15- 19  F5.2  s      RAs     Right Ascension B1950 (seconds)
          22  A1    ---    DE-     Declination B1950 (sign)
      23- 24  I2    deg    DEd     Declination B1950 (degrees)
      26- 27  I2    arcmin DEm     Declination B1950 (minutes)
      29- 32  F4.1  arcsec DEs     Declination B1950 (seconds)
      35- 40  F6.3  mag    Bjsel   Final bj magnitude with extinction correction
                                    (BJSEL) (G2)
      43- 49  F7.1  ---    psi     psi classification parameter (PROB) (2)
      51- 55  F5.3  ---    k       k classification parameter = k/k_star (PARK)
      57- 61  F5.3  ---    mu      mu classification parameter = mu/mu_star (PARMU)
      63- 64  I2    ---    Cl      [-4,2] Final classification (IGAL) (3)
      66- 67  I2    ---    jon     [0,9]?=-1 Eyeball classification (JON) (G3)
      69- 71  I3    deg    ora     [0,180[ Orientation angle E-(N)-W (ORIENT)
      72- 73  A2    ---    ---     [.0]
      75- 79  F5.3  ---    e       Eccentricity (ECCENT)
      82- 86  I5    pix    Area    Isophotal area in pixels (AREA)
          87  A1    ---    ---     [.]
      89- 96  F8.1  pix    Xpos    Bj plate position in 8 micron pixels (X_BJ)
      98-105  F8.1  pix    Ypos    Bj plate position in 8 micron pixels (Y_BJ)
     108-110  I3   0.01pix dX      ?=-99 Distortion difference (X(Bj)-X(R))*100 (DX)
         111  A1    ---    ---     [.]
     114-116  I3   0.01pix dY      ?=-99 Distortion difference (Y(Bj)-Y(R))*100 (DY)
         117  A1    ---    ---     [.]
     120-125  F6.3  mag    Bjmag   Final bj magnitude (BJG) (1)
     128-132  F5.2  mag    Rmag    Unmatched APM 'total' mag (RMAG)
     135-139  F5.2  mag    Pmag    ?=0 Unmatched raw APM profile integrated
                                       magnitude (PMAG)
     142-146  F5.2  mag    Fmag    ?=0 Unmatched raw APM 2" profile integrated
                                       magnitude (FMAG)
     149-153  F5.2  mag    Smag    ?=0 Unmatched raw stellar mag from APMCAL (SMAG)
     157-160  A4    ---    ---     [0.00]
     162-164  I03   ---    UKST    UKST field number (IFIELD)
     167-171  I5    ---    Igal    Galaxy number in UKST field (IGFIELD)
     174-183  A10   ---    Name    2dFGRS assigned name (4)
     186-190  F5.2  mag   Bjmag.o  Original bj magnitude (BJG_OLD) (1)
     192-196  F5.2  mag   Bjsel.o  Original bj magnitude with extinction
                                      correction (BJSELOLD)
     199-203  F5.2  mag   Bjmag.1  bj magnitude in 100k (VII/226) (100_BJG) (1)
     205-209  F5.2  mag   Bjsel.1  bj magnitude in 100k release (VII/226) with
                                      extinction correction (100BJSEL)

    Note (1): without extinction correction.

    Note (2): psi parameter is defined as:
         -- for eyeballed galaxies:
            psi*1000 =  (10000 + abs(jon) + psi*100)
         -- for eyeballed non-galaxies:
            psi*1000 = -(10000 + abs(jon) + psi*100)
    Note (3): the class is numbered as follows:
         -4 = noise
         -3 = star + star
         -2 = star + fuzz
         -1 = star
          0 = galaxy + star merger
          1 = galaxy
          2 = galaxy + galaxy merger
    Note (4): name is blank if either  (i) Bjsel.o is fainter than 19.45, or
         (ii) the object could not be allocated to a fibre by the configuration
         algorithm.

    Global Notes:

    Note (G1): eta is a parameter derived from a Principal Component Analysis
         of the spectrum; it is negative for early-type galaxies, positive
         for later-type galaxies. See details in Madgwick et al.,
         2002MNRAS.333..133M
    Note (G2): bj magnitude with extinction correction means: corrections for
         isophote, field-effects and plate-matching, then calibrated to total
         mags with  saturation correction, and then extinction corrected.
    Note (G3): Eyeball classification of galaxies is a positive value
               for galaxies brighter than about 18th mag, as follows:
          0 = noise
          1 = S0
          2 = elliptical
          3 = spiral
          4 = irregular
          5 = undetermined galaxy
          6 = star
          7 = star + star merger
          8 = galaxy + star merger
          9 = galaxy + galaxy merger
          Values between 11 and 19 may also be found.

    History:
        From http://www.mso.anu.edu.au/2dFGRS/
    ================================================================================
    (End)                                   Francois Ochsenbein [CDS]    18-Dec-2007