Priors format in Redrock

Implementation

The implementation was done in (PR #152) and updated in (PR #194)

Prior form available

• gaussian –> the amplitude is set to one. I (Edmond) noticed it is not always sufficient –> in this case use tophat prior

• lorentzien –> same remark than above

• tophat –> useful if you really trust the region where you want to search. Use for the clustering QSO catalog in DESI

Use prior in RR

• Build a prior file as explained above. The prior_file as to contain a prior for every targetid on which redrock will be run

• Use the flag : –priors filename_priors during the execution of rrdesi

Prior file

• I (Edmond) give here a minimal function to write in a correct way the prior file (see raw file –> problem of render with github…):

import numpy as np
import fitsio

def write_prior_for_RR(targetid, z_prior, filename_priors):
    """
        Minimal fonction to write prior file for redrock.

        targetid : must be the array of targetid list given to redrock in the rrdesi command
        z_prior  : array of size targetid.size containing the prior value of the redshift for the considered targetid. For instant value from QuasarNet.
        filename_priors : name of the prior file which will be given to the rrdesi command

    """

    # need to be the same for every target
    # only function[0] will be read in the prior class !
    function = np.array(['tophat'] * z_prior.size)

    # can be different for every target (I set it constant here)
    sigma = 0.1*np.ones(z_prior.size)

    # save
    out = fitsio.FITS(filename_priors, 'rw', clobber=True)
    data, names, extname = [targetid, function, z_prior, sigma], ['TARGETID', 'FUNCTION', 'Z', 'SIGMA'], 'PRIORS'
    out.write(data, names=names, extname=extname)
    out.close()

    print(f'     Write prior file for RR with {z_prior.size} objetcs: {filename_priors}')