Spectral Extraction

Extracting a 1D spectrum from the JWST IFU cube with CRETA

(Enabled but not supported in the current v1.0.0 of CAFE)

The user can employ CRETA to extract a continuous or discontinuous spectrum from one, some, or all data cubes that the user has copied and made available in the input_data/ directory. Currently CRETA supports the extraction of individual spectra; that is, extractions along a single line-of-sight, or position in the sky. CRETA will extract the spectrum based on a set of parameters provided by the user in a parameter file. Inside it, the user can specify:

cubes: The cubes to be extracted (currently, only MIRI/MRS; the names provided here need to match or be a sub-string of the cube file names)

user_r_ap: The radius of the circular aperture used for the extraction

user_ra, user_dec: RA and Dec coordinates of the source

point_source: The method of extractions (point source: cone extraction, with radius increasing linearly with wavelength; extended source: cylinder extraction, with constant radius)

lambda_ap: Wavelength reference for the definition of aperture radius (if point source extractions; ignored otherwise)

aperture_correction: Whether to perform aperture correction based on PSF cubes

centering: Whether to perform a centroid centering on the user provided coordinates

lambda_cent: Wavelength at which the centering will be performed (ignored otherwise)

background_sub: Whether to perform an annulus-based background subtraction prior to the aperture photometry

r_ann_in: Inner radius of the background annulus (ignored otherwise)

ann_width: Width of the background annulus (ignored otherwise)

Options for directory setup (specified in the command execution only):

data_path (default: CRETA/data/)

PSFs_path (default: CRETA/PSFs/)

output_path (default: CRETA/extractions/)

output_filebase_name (default: ‘last_result’)

parfile_path (default: CRETA/param_files/)

parfile_name (default: ‘single_params.txt’)

CRETA will return a ‘_cube.fits’ file containing the extracted spectrum, which can be fed directly to CAFE for fitting.

The specific steps to achieve this will be included in future releases in a jupyter notebook in the notebooks/ folder in the GitHub repository.