2dFGRS Final Data Release
Survey Mask Software

  1. The survey masks

    The survey masks distributed with the 2dFGRS Final Data Release are described here and in Colless et al. (2001) and Norberg et al. (2002). This version of the masks and mask software includes the mu-masks described in Colless et al. (2001) but not included in the original 100k release. It provides finer resolution in the masks, improvements to the speed of the code, and a correction for a minor bug that gave slightly incorrect positions for some of the holes in the survey.

  2. Copyright and use of the mask codes

    As a user of the mask codes, we request that you observe the following guidelines:

    • The code provided here has been written by several members of the 2dFGRS team. Peder Norberg and Shaun Cole (University of Durham, UK) wrote the software used to create the survey masks. If you use any part of this 2dFGRS software, please acknowledge "the 2dFGRS mask software by Peder Norberg and Shaun Cole".
    • This code is supplied as-is and without guarantees - use it with caution and report any bugs.
    • Read all of the documentation before trying to use the code!

  3. The mask data files

  4. Magnitude limit masks

    The NGP and SGP magnitude limit masks are shown below.

  5. Redshift completeness masks

    The NGP and SGP redshift completeness masks are shown below.

  6. Mu-masks

    The NGP and SGP mu-masks are shown below.

  7. Example code for using the masks

    • Copy the following files:
    • Choose the right compiler for your machine by selecting/deselecting the appropriate lines in the makefile. This code has been tested on Sun Solaris, DEC Alpha and PC Linux (with the Intel ifc compiler).
    • Given R.A. and Dec. (B1950, in radians), release returns the completeness, the magnitude limit, the mu value and the UK Schmidt Telescope (UKST) sky survey plate number at that particular position. When compl = -1, the given position is outside the main 2dF boundary; when compl = -2, the given position is inside an excluded region (a 'hole').

  8. Generating selected samples and mock catalogues

    • Introduction: As well as the example code above, we also provide code for selecting subsets of the survey data (using various criteria defined by the user - see below) and generating an associated unclustered catalogue of with the same set of selection criteria. By changing various flags one can create volume- or magnitude-limited catalogues, select galaxies within a given range in absolute or apparent magnitude, choose only those with a given spectral class or simply select galaxies within a given redshift range or within regions of given completeness. The main purpose of this code is the generation of the associated distribution of unclustered galaxies with the same selection criteria (a mock catalogue).

    • Installing the code: Create a directory to work in and copy to it release_230k.tar.gz (468Mb uncompressed, 50Mb compressed) and aux_data.tar.gz (168Mb uncompressed, 120Mb compressed). Gunzip and untar these files. This will produce the following directories:
      If you do not have Starlink libraries on your system, also copy to the working directory fitsio.tar.gz (1.5Mb uncompressed, 0.2Mb compressed) and sla.tar.gz (0.9Mb uncompressed, 0.2Mb compressed). The source code for these routines comes from the Starlink website, but has been slightly modifications so as to also work with the Intel ifc compiler under Linux. Gunzip and untar these to produce the following directories:
      Finally, copy to the working directory select_release.tar.gz (0.8Mb uncompressed, 0.2Mb compressed). Gunzip and untar this to produce:
            main/selection_release.f     # sample selection and mock catalogue code
            sub/dist.for                 # subroutines used by the main codes
            sub/allheaders.dat           # additional data files
            sub/rancentres.txt           # data files for the random fields
            seldir/selfile.230k.2df_sgp  # selection function files
            outdir/                      # directory for output
      Choose the right compiler for your machine by selecting/deselecting the appropriate lines in the makefile. This code has been tested on Sun, Alpha Dec and Linux (with the Intel ifc compiler).

    • Running the code: The script select_release.com compiles the executable select_release and runs it for the parameters contained in the script. These parameters, which can be changed by the user, are described (with typical values) below:
            # Switches with F (false) and T (true) options
            set dirp = release_230k   # Directory from which to read the files
            set recalib = F           # No influence for this version of code
            set mock = F              # Selection made from a mock catalogue?
            set vlim = F              # Create a volume limited sample?
            set mag_fix = F           # Use fixed magnitude limit?
            set mu_mask = T           # Use mu mask correction?
            set magerr = F            # Apply magnitude errors?
            set zzerr = F             # Apply redshift errors?
            set spec = F              # Using spectral class information?
            # Basic selection criteria
            set zmin = 0.002          # Minimum redshift considered
            set zmax = 0.3            # Maximum redshift considered
            set magmin = 15.0         # Bright apparent magnitude considered
            set magmax = 19.35        # Faint apparent magnitude considered
                                      # (has no effect unless mag_fix = T) 
            set compl_cut = 0.5       # Sector completeness cut
            set iseed = -75843        # Initial random seed (needs to be
                                      # changed when creating a set of
                                      # different mock catalogues)
            set ng_ranmult = 1        # Multiple of the number of galaxies
                                      # produced for the mock catalogues
                                      # (if <= 0, no mocks are produced)
            set region = sgp          # Region analyzed: ngp, sgp or ran
            # The value of region is correctly assigned (within the code) to
            # pick up the appropriate input files
            # Names of various mask files that are read in
            set maskfile = $dirp"_reg/mask.dat"
            set maglimmask = $dirp"/maglim_mask.reg.dat"
            set mumaskfile = $dirp"_reg/mask_mu.dat"
            set selfile = seldir/selfile.$dir.2df_reg  # Selection function file  
            set catname = $dirp"/parent.reg.txt"       # 2dFGRS catalogue
            set file1 = $dirp"_reg/weight.txt"         # 1st list of weights
            set file2 = $dirp"_reg/weight_extra.txt"   # 2nd list of weights
            # Names of output files:
            set outfile1 = "outdir/select_real_"$region".out" # selected data 
            set outfile2 = "outdir/select_mock_"$region".out" # mock catalogue
            # Additional selection criteria useful only if you want to
            # select volume limited subsets of the data, possibly with
            # additional selection on magnitudes and eta:
            set nlim = 0
            # nlim=0 : values of lim_spec (below) ignored
            # nlim=1 : construct a volume limited catalogue defined by
            #          the absolute magnitude limits lim_spec1 & lim_spec2
            # nlim=2 : within the volume limit select only galaxies with
            #          absolute magnitudes between lim_spec3 and lim_spec4
            # nlim=3 : within this subset select only galaxies with
            #          eta value between lim_spec5 and lim_spec6
            # This pair of parameters define the limit of the volume
            set lim_spec1 = -20.5  # Bright absolute magnitude limit
            set lim_spec2 = -20.0  # Faint absolute magnitude limit
            # This pair define the absolute magnitude range of the galaxy
            # sample that is returned. These magnitude limits must lie within 
            # the magnitude range (lim_spec1,lim_spec2) that defines the
            # sample volume. 
            set lim_spec3 = -20.5  # Bright absolute magnitude limit
            set lim_spec4 = -20.0  # Faint absolute magnitude limit
            # This pair allow selection using spectral class information
            set lim_spec5 = -5.0   # Lower eta limit 
            set lim_spec6 = +60.0  # Upper eta limit
    • Inputs: The main input is the galaxy input catalogue ($dirp/parent.reg.txt). The format of this file is explained in the description of the spectral catalogues. Other versions can be created fairly straightforwardly from the mSQL database. The other input files will always be the sam ( provided you don't change the pixel scale) and therefore do not need to be updated. Currently the pixel scale is set to 1.4arcmin x 1.4arcmin, but can be improved by changing the variables NPX and NPY (defined in the main programs) accordingly; 1.4' x 1.4' corresponds to NPX=2*1800 and NPY=2*600. Note that the pixel scale needs to be the same as the one used in generating the masks.

    • Outputs: select_release.exe outputs two files - one for the selected data (in outfile1) and one for the randoms (in outfile2). If you want to change the format of these two files, you can do so by setting the code variable write_cat=.false. and inserting your own code at the bottom of program selectdata as indicated in the code. The standard format of the output is:
            ra      = galaxy R.A. (B1950)
            dec     = galaxy Dec. (B1950)
            zz      = best galaxy redshift 
            mag     = galaxy b_J magnitude 
            wsel    = weight assigned by 10 nearest neighbours (equal to 1 if
                      all neighbours have a good quality redshift; typically
                      equal to 2 if all 10 nearest neighbours are missing)
            compl   = completeness of associated sector 
            selz    = selection function value for galaxy (without mu_mask)
            selz_mu = selection function value for galaxy (with mu_mask)
            bjlim   = b_J magnitude limit
            serial  = galaxy serial number (only for real data, not mocks;
                      identical to the one listed in $dirp/parent.reg.txt)
    • Notes on the code:
      • Some additional files are produced by these programs and used at different stages of the analysis; these files are not relevant to the user.
      • There are a few parameters that are set within the main program rather than in the script. These have been set to typical values, but can be changed at the user's discretion (and risk).
      • The program uses a Omega=0.3, Lambda=0.7 cosmology by default.

  9. Limitations and corrections

    • Each pixel in the masks is 1.4 arcmin on a side. This is much larger than the precision of the 2dFGRS galaxy positions. Hence the masks can indicate that some 2dFGRS galaxies are outside the survey boundary or inside excluded holes due to pixelisation effects, as the masks have been defined in a conservative way.

    • In the definition of the magnitude-dependent completeness mask in section 8.3 of Colless et al. (2001), there is an error in the value given for the parameter alpha; the paper gives alpha=0.5, but the correct value is alpha=0.5ln(10).

    Please report any serious problems encountered with this software to the 2dFGRS team.

Matthew Colless, colless@aao.gov.au, Fri 7 Jul 2006, 156th access