Galaxy Photometry Resource Needs

Each of the SV Requirements / Goals will need a page describing what is needed to conduct the test or meet the goal. Here is a suggested breakdown. In the near term, we are most concerned with the data processing needs (i.e. what will DESDM or some alternative pipeline need to do).

Of course the answers to many of these questions will not be known until we proceed further in our planning, but we should fill in what we know.

Number/name of Requirement or Goal: Galaxy Detection & Photometry goals Gal-G1 through Gal-G7 combined

DECam observations

  • Field(s) to observe:
    • Fields that overlap with the truth tables: VVDS, CDFS, CFHTLS
  • Number, duration of exposures per filter
    • Main survey single-epoch depth exposures
  • Dithering / tiling pattern:
    • Gal-G6: undithered, consecutive pairs of exposures in each of grizY
    • Gal-G7: undithered between grizY exposures of truth field
    • Gal-G7: standard main survey 10-tiling pattern of a single field
  • Sky conditions needed (seeing, photometric, moon phase, etc:):
    • Photometric, standard main survey observing conditions
    • In addition for Gal-G1, we want data over a range of seeing, say 0.5"-2"
  • Other timing constraints:
    • Gal-G6: pairs of exposures in each filter should be consecutive to minimize changes in observing conditions

Data processing needs

Which of the following products would you need to conduct the test:

  • Raw images available at some off-mountain site? no, unless we need to process images to catalogs outside of DESDM
  • Images with cross-talk, debias, trim, dome-flat correction? yes, standard DESDM detrending
  • Images with an "illumination" or "star" flat applied for better relative photometry? yes, if available
  • Single-exposure object catalogs? yes
    • with astrometric solution accurate to: standard DES requirement 100 mas, in particular to match truth catalogs
    • and photometric zeropoint accurate to: 0.05 mag
    • Only need bright stars, or also want galaxy magnitudes? want galaxy model fitting photometry and detmodel colors
  • Registered stacked images (co-adds)?
    • Goals Gal-G1 through Gal-G6 written with single-epoch data/catalogs in mind, but can be translated to coadd data/catalogs if available
    • PSF homogenization needed? not required
  • Catalogs from coadds?
    • Goals Gal-G1 through Gal-G6 written with single-epoch data/catalogs in mind, but can be translated to coadd data/catalogs if available
    • with photometric zeropoint (and/or colors) accurate to: 0.05 mag
  • Weight maps? standard DESDM masks desirable
    • Bad & saturated pixels? yes
    • Bright-star exclusion zones? yes
    • other?
  • Polygon masks?
  • Difference images?
  • Further SN data products:
  • Other: Truth tables uploaded to the DESDM database; TrivialAccess

Telescope or other engineering data

External data sets

  • Truth table catalogs (we should have the catalogs uploaded to the DESDM database, so that all analyzers can retrieve them using TrivialAccess):
    • VVDS
    • CFHTLS
    • CDFS **

Codes and scripts for analysing the test data

  • Gal-G2: existing 2dPhot code for completeness measurements
  • For other tests, existing or TBD IDL and/or Python scripts
  • At least some of the code is be accumulated in repository SV_GAL


Are there real-time decisions to be made during the observations?
  • Gal-G1: Real-time decisions need to be made to take data for this test under range of seeing conditions 0.5"-2"
  • Otherwise only requires standard main survey observing conditions
How quickly can / must the data be available and analysed?
  • No time requirement
Who will do it, and where?
  • Ideally DESDM provides SExtractor catalogs, but if not available we plan to have offline processing/cataloging capability (using DESDM pipeline code) for these tests at Fermilab

Other important resources or things to note