.. _visualisation_wedge: 2D Light-cone Wedge Plot ======================== ``scripts/plot_lightcone_wedge.py`` .. contents:: On this page :local: :depth: 1 ---- Overview -------- The wedge plot renders a thin declination slice of a galaxy redshift survey in polar coordinates centred on the observer (Earth): .. math:: r \;=\; d_C(z) \quad [\text{Mpc}], \qquad \theta \;=\; \alpha \quad [\text{RA, radians}] where :math:`d_C(z)` is the comoving distance computed with the Planck 2018 flat ΛCDM cosmology (:math:`H_0 = 67.4\,\text{km\,s}^{-1}\text{Mpc}^{-1}`, :math:`\Omega_m = 0.315`). The observer sits at the origin; the fan opens to the right. Each galaxy is coloured by its redshift using the *turbo* colormap. Concentric arcs mark comoving distance milestones and are labelled with both :math:`d_C` [Mpc] and the corresponding redshift and lookback time [Gyr]. The script produces: * **Individual wedge** for every requested survey, using that survey's built-in optimal footprint slice (RA range and DEC window) unless the user overrides them. * **Combined wedge** (when more than one survey is requested) with each survey shown in a distinct solid colour. ---- Supported catalogues -------------------- .. list-table:: :header-rows: 1 :widths: 14 40 10 10 10 16 * - Key - FITS file - RA col - DEC col - z col - Default DEC window * - ``LS10`` - ``~/data/legacysurvey/dr10/sweep/BGS_VLIM_Mstar/`` ``LS10_VLIM_ANY_11.5_…_DATA.fits`` - ``RA`` - ``DEC`` - ``BEST_Z`` - 0° ± 3° * - ``GAMA`` - ``~/data/GAMA/FULL_CATALOG_PROSPECT_MASSES.fits`` - ``RA`` - ``DEC`` - ``Z`` - 0° ± 3° * - ``SDSS`` - ``~/data/SDSS/MPA_JHU/full_MERGED.fits`` - ``RA`` - ``DEC`` - ``Z`` - 0° ± 2° * - ``DESI_NGC`` - ``~/data/DESI/DR1/BGS_ANY_NGC_clustering.dat.fits`` - ``RA`` - ``DEC`` - ``Z`` - 35° ± 12° * - ``DESI_SGC`` - ``~/data/DESI/DR1/BGS_ANY_SGC_clustering.dat.fits`` - ``RA`` - ``DEC`` - ``Z`` - 0° ± 5° Quality cuts applied to every catalogue: RA ∈ [0°, 360°], DEC ∈ [−90°, 90°], :math:`z > 0`, and ``ZWARNING = 0`` where that column exists. ---- Usage ----- Each survey is plotted with its own optimal footprint by default: .. code-block:: bash # All surveys — individual plots + combined, using per-survey defaults python scripts/plot_lightcone_wedge.py # DESI NGC only, dark background python scripts/plot_lightcone_wedge.py --surveys DESI_NGC --dark # GAMA G09+G12+G15 fields, dark background python scripts/plot_lightcone_wedge.py --surveys GAMA --dark # Equatorial combined: GAMA + SDSS + DESI NGC (explicit DEC requires --force-dec) python scripts/plot_lightcone_wedge.py \ --surveys GAMA SDSS DESI_NGC \ --ra-min 120 --ra-max 240 \ --dec-center 0 --dec-width 2 --force-dec --dark # All five surveys, equatorial strip, dark background python scripts/plot_lightcone_wedge.py \ --surveys LS10 GAMA SDSS DESI_NGC DESI_SGC \ --ra-min 120 --ra-max 240 \ --dec-center 0 --dec-width 2 --force-dec --dark ---- Command-line options -------------------- .. list-table:: :header-rows: 1 :widths: 22 14 64 * - Option - Default - Description * - ``--surveys`` - all five - Space-separated list of catalogue keys to plot. Choices: ``LS10 GAMA SDSS DESI_NGC DESI_SGC``. * - ``--dec-center`` - ``0.0`` - Centre of the DEC slice in degrees. For individual plots this is overridden by each survey's built-in default unless ``--force-dec`` is also set. * - ``--dec-width`` - ``2.0`` - Half-width of the DEC slice in degrees. * - ``--force-dec`` - (flag) - Apply ``--dec-center`` / ``--dec-width`` to individual plots too, instead of each survey's built-in DEC default. * - ``--zmax`` - ``0.45`` - Maximum redshift shown. * - ``--ra-min`` - ``0.0`` - RA lower bound [degrees]. Value ``0`` signals "use survey default". * - ``--ra-max`` - ``360.0`` - RA upper bound [degrees]. Value ``360`` signals "use survey default". * - ``--max-points`` - ``200 000`` - Maximum number of galaxies plotted per survey (random downsampling applied when exceeded). * - ``--dark`` - (flag) - Use a dark (#0a0a0a) background instead of white. * - ``--seed`` - ``42`` - Random seed for the downsampling step. * - ``--no-individual`` - (flag) - Skip the per-survey individual plots; produce only the combined figure. * - ``--no-combined`` - (flag) - Skip the combined multi-survey figure. * - ``--output-dir`` - ``results/wedgePlots`` - Directory where PNG files are written (created if absent). ---- Output files ------------ Individual wedge ~~~~~~~~~~~~~~~~ .. code-block:: text wedge_{SURVEY}_zmax{Z:.2f}_dec{DEC:.1f}_w{WIDTH:.1f}_{dark|light}.png Example: ``wedge_DESI_NGC_zmax0.45_dec35.0_w12.0_dark.png`` Combined wedge ~~~~~~~~~~~~~~ .. code-block:: text wedge_combined_zmax{Z:.2f}_dec{DEC:.1f}_w{WIDTH:.1f}_{dark|light}.png Example: ``wedge_combined_zmax0.45_dec0.0_w2.0_dark.png`` ---- Example outputs --------------- DESI DR1 BGS Northern Galactic Cap ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 200 000 galaxies from DESI DR1 BGS NGC, declination slice 35° ± 12°, RA = [120°–250°], coloured by redshift. .. figure:: ../figures/visualisation/wedge_DESI_NGC_zmax0.45_dec35.0_w12.0_dark.png :width: 90% :alt: DESI DR1 BGS NGC light-cone wedge, DEC = 35° ± 12°, RA = 120°–250°, z < 0.45 **DESI DR1 BGS NGC** — 200 000 galaxies in a 24°-wide declination slice centred at DEC = 35°. The cosmic web is visible as an alternation of dense filaments (bright, yellow–red) and underdense voids (dark gaps). ---- GAMA survey ~~~~~~~~~~~ GAMA G09 + G12 + G15 equatorial fields, declination slice 0° ± 3°, RA = [129°–222°]. .. figure:: ../figures/visualisation/wedge_GAMA_zmax0.45_dec0.0_w3.0_dark.png :width: 90% :alt: GAMA light-cone wedge, DEC = 0° ± 3°, RA = 129°–222°, z < 0.45 **GAMA** — three equatorial fields (G09, G12, G15) separated by survey gaps. The lower galaxy density compared to DESI reflects GAMA's smaller area and deeper target selection. ---- Combined equatorial slice ~~~~~~~~~~~~~~~~~~~~~~~~~ GAMA + SDSS MPA-JHU + DESI NGC overlaid in a 4°-wide equatorial strip, RA = [120°–240°]. Each survey is drawn in a distinct colour. .. figure:: ../figures/visualisation/wedge_combined_zmax0.45_dec0.0_w2.0_dark.png :width: 90% :alt: Combined wedge — GAMA, SDSS, DESI NGC, equatorial strip, z < 0.45 **Combined wedge.** Green: GAMA; pink: SDSS MPA-JHU; blue: DESI DR1 BGS NGC. DESI's greater depth and area are evident. The three surveys overlap in the G12 and G15 fields (RA ≈ 180°–222°), allowing cross-survey comparisons.