Multiband analysis

multiBandDriver.py perform multiband analysis. This procedure merge the detection catalog generated in coaddDriver.py for each filter, perform photometry in every filter and generate new photometric catalog. Description of multiBandDriver.py describes the detailed procedure of multiband analysis. hscPipe5 or later also perform PSF-matched photometry in multiBandDriver.py.

# Directory for reduction is ~/HSC and rerun name test. Filters are g, i2 and r2.
# In case of using local system,
multiBandDriver.py ~/HSC --calib ~/HSC/CALIB --rerun test --id tract=0 filter=HSC-G^HSC-I2^HSC-R2 --batch-type=smp --cores=8

# multiBandDriver.py [data reduction directory] --calib [calib directory] --rerun [rerun name] --id tract=[tract] filter=[filter1^filter2^...]
# Option
#       --id: Specify all data used in multiband analysis.

As a first step, multiBandDriver.py collects the positional information of the detected objects in det catalog and creates new merge catalogs (mergeDet). Based on the mergeDet catalogs, it performs photometry on the coadd images in each filter (meas). In this process, the objects are deblended to child objects when needed. In this measurement, the centroids and object shapes vary from filter to filter. Then the object information is collected again and one reference catalog is created (ref). Finally, the measurements are performed again, then final photometric catalogs (forced_src) are generated.

The catalogs generated with multiBandDriver.py are summarized below:

  • Merged catalog of det catalogs for all filters: rerun/[rerun]/deepCoadd-results/merged/[tract]/[patch]/mergeDet-[tract]-[patch].fits
  • Photometric catalog of the sources listed in mergeDet measured on coadd images: rerun/[rerun]/deepCoadd-results/[filter]/[tract]/[patch]/meas-[filter]-[tract]-[patch].fits
  • Match list of objects in mergeDet catalog with reference catalog: rerun/[rerun]/deepCoadd-results/[filter]/[tract]/[patch]/srcMatch-[filter]-[tract]-[patch].fits
  • List of object photometry and their matched reference catalog: rerun/[rerun]/deepCoadd-results/[filter]/[tract]/[patch]/srcMatchFull-[filter]-[tract]-[patch].fits
  • List of sources based on meas catalog (final photometry is performed based on this catalog): rerun/[rerun]/deepCoadd-results/merged/[tract]/[patch]/ref-[tract]-[patch].fits
  • Source catalog generated by a forced photometry: rerun/[rerun]/deepCoadd-results/[filter]/[tract]/[patch]/forced_src-[filter]-[tract]-[patch].fits

Their schema files are found in rerun/[rerun]/schema.

Warning

The name of column in these catalogs are different from the ones generated with hscPipe4.

Multiband analysis performs photometry in several methods.

  • Aperture photometry with fixed radii
    • base_CircularApertureFlux_[3,4,6,9,12,17,25,35,50,70]_[0,5]_flux (fixed radius = [3.0, 4.5, 6.0, 9.0, 12.0, 17.0, 25.0, 35.0, 50.0, 70.0])
  • PSF model photometry (Default PSFEx is used for modeling. Useful for point sources.)
    • base_PsfFlux_flux
  • CModel photometry (Fitted by combination of Sersic profiles with Sersic indices n = 1 and 4. Useful for extended sources like galaxies.)
    • base_CmodelFlux_flux
  • Kron photometry
    • base_KronFlux_flux

The results of PSF-matched photometry is also included in forced catalog. For example,

  • ext_convolved_ConvolvedFlux_seeing: Original seeing (in sigma)
  • ext_convolved_ConvolvedFlux_[0,1,2,3]_kron_flux: Kron flux measured after matching the seeing on the images to [3.5,5.0,6.5,8.0] pixels
  • ext_convolved_ConvolvedFlux_[0,1,2,3]_[3_3,4_5,6_0]_flux: aperture flux measured with fixed pixel ([3.3,4.5,6.0] pixels) aperture radii after matching the seeing on the images to [3.5,5.0,6.5,8.0] pixels

FLAGS are in 2d array named flags. Please see FLAG numbers at fits header of forced*fits. If flags start from TFLAG=1 and you want to see the FLAG with TFRAG=56, you can get them by e.g.,

>>> from astropy import fits
>>> hdul=fits.open(“forced_*fits”)
>>> hdul[1].data[“flags”][…,56-1]

Note that TFLAG do not always correspond to same flag type. Please check your fits header every files.

Other parameters listed in catalog can be checked in a schema file (e.g., forced_src schema file).