image_table_to_catalog

romanisim.catalog.image_table_to_catalog(table, bandpasses)

Read an astropy Table into a list of CatalogObjects.

We want to read in an image catalog and make a list of CatalogObjects. The image catalog indicates that specific galaxies stored as images in a RealGalaxyCatalog should be rendered at specific locations in the images, for example, if one had postage stamps of galaxies from a hydrodynamical simulation and wanted to render them in a Roman simulation. The table must have the following columns:

• ra : float, right ascension in degrees

• dec : float, declination in degrees

• ident: int, identity entry in RealGalaxyCatalog

• dilate: float, how much to dilate the image by, in degrees

• rotate: float, how much to rotate the image by

• shear_ba: how much to shear the image by

  (new minor over major axis, if the original image were round)

• shear_pa: angle to shear the image on, in degrees

Additionally there must be a column for each bandpass giving the total flux in that bandbass, integrating over the image.

The file name for the RealGalaxyCatalog must be present in the ‘real_galaxy_catalog_filename’ keyword in the table metadata.

Note that GalSim tries to deconvolve the image by the RealGalaxyCatalog PSF before reconvolving it with the appropriate filter PSF. Depending on the dilation factor and the RealGalaxyCatalog PSF, this can require substantial deconvolution and lead to ringing. For sufficiently large dilations, any initial PSF will become larger than the Roman PSF and induce ringing.

Parameters:

tableastropy.table.Table

astropy Table containing ra, dec, ident, dilate, rotate, shear_amount, shear_pa, and fluxes in different bandpasses. Metadata must include real_galaxy_catalog_filename pointing to the RealGalaxyCatalog to use.

bandpasseslist[str]

list of names of bandpasses. These bandpasses must have columns of the corresponding names in the catalog, containing the objects’ fluxes.

Returns:

list[CatalogObject]

list of catalog objects for catalog