def convert_dm_ref_zp_flux_to_nanoJansky(flux, dm_ref_zp=27):
    """Convert the listed DM coadd-reported flux values to nanoJansky.

    Eventually this function should be a no-op.  But presently
    The processing of Run 1.1, 1.2 to date (2019-02-17) have
    calibrated flux values with respect to a reference ZP=27 mag
    The reference catalog is on an AB system.
    Re-check dm_ref_zp if calibration is updated.
    Eventually we will get nJy from the final calibrated DRP processing.
    """
    AB_mag_zp_wrt_Jansky = 8.90  # Definition of AB
    AB_mag_zp_wrt_nanoJansky = 2.5 * 9 + AB_mag_zp_wrt_Jansky  # 9 is from nano=10**(-9)
    calibrated_flux_to_nanoJansky = 10**((AB_mag_zp_wrt_nanoJansky - dm_ref_zp)/2.5)

    return calibrated_flux_to_nanoJansky * flux