DOI: 10.5281/zenodo.7143381
title: Preliminary updates to the NIRCam photometric calibration

description: Reposted from https://github.com/gbrammer/grizli/pull/107 to make a more permanent reference. As of late August 2022, a number of groups have found that there still seem to be large corrections to the individual NIRCam SCA photometric calibration required, even after the CRDS updates in late July. There is a series of ongoing calibration programs that will establish the absolute calibration of all of the modes at high precision. For now, however, those calibration data are incomplete. I have derived some corrections to the <code>jwst_0942.pmap</code> context using the following: The flux calibration standard <code>J1743045</code> suggests that the absolute NIRISS calibration is quite good, with just a correction of 1/1.04 required for F200W The flux standard also suggests that NIRCam LW broadbands are fairly well calibrated, perhaps with the exception of a 1/0.912 correction needed for F444W The flux standard data are currently only available for the B module in some filters. To calibrate the A module and also the additional broadband SW filters, I derived <em>relative</em> corrections using the wealth of data taken of the LMC astrometric calibration field, where certain patches of the field have been observed by more than one NIRCam SCA. The corrections are derived by measuring photometry in the NIRISS broad bands and then calculating scale factors of all of the NIRCam SW SCAs relative to these. Relative A/B corrections for the NIRCam LW broad-band filters are also derived from the LMC data. The tabulated values in <code>grizli/data/photom_correction.yml</code> are the median ratios of the derived flux densities in the indicated filters to some reference, either relative or absolute. To apply the corrections relative to exposures calibrated with the current CRDS_CONTEXT, the values should be <em>divided</em> from the SCI and ERR arrays, which is now implemented in <code>utils.drizzle_from_visit</code>. The LMC mosaics are available at https://s3.amazonaws.com/grizli-v2/JwstMosaics/lmc-astrometric-field/lmc.html. The full notebook used to derive the LMC corrections is at https://s3.amazonaws.com/grizli-v2/JwstMosaics/lmc-astrometric-field/astrometric-field-photometry.ipynb. This release includes a table (summary_0989.txt) of my photometric calibration determinations and comparisons of these to the CRDS references. An official update from the NIRCam team is now available in the JWST CRDS system in jwst_0989.pmap. Please cite this DOI if you use the "v4" mosaics of JWST imaging fields produced by G. Brammer. <pre><code># det filt pupil mjsr_0942 gbr ila mjsr_gbr file gbr_inv mjsr_0989 file_0989 ratio_989_gbr # mjsr_0942 : PHOTMJSR from jwst_0942.pmap # gbr : multiplicative corrections from G. Brammer # ila : multiplicative corrections from I. Labbe # mjsr_gbr = gbr * mjsr_0942 # 0942 numbers from jwst_nircam_photom_0[file].fits # mjsr_0989 : PHOTMJSR from jwst_0989.pmap # 0989 numbers from jwst_nircam_photom_0[file_0989].fits # ratio_989_gbr = mjsr_0989 / mjsr_gbr NRCA1 F090W CLEAR 3.762 0.826 --- 3.108 106 1.210 2.996 116 0.964 NRCA1 F115W CLEAR 3.299 0.914 0.876 3.014 106 1.094 2.963 116 0.983 NRCA1 F150W CLEAR 2.460 0.936 0.895 2.303 106 1.068 2.251 116 0.978 NRCA1 F200W CLEAR 2.211 0.865 0.846 1.913 106 1.155 1.892 116 0.989 NRCA2 F090W CLEAR 3.872 0.833 --- 3.224 100 1.201 3.282 110 1.018 NRCA2 F115W CLEAR 3.395 0.908 0.867 3.084 100 1.101 3.101 110 1.006 NRCA2 F150W CLEAR 2.531 0.937 0.894 2.371 100 1.067 2.384 110 1.005 NRCA2 F200W CLEAR 2.275 0.889 0.857 2.023 100 1.125 2.081 110 1.029 NRCA3 F090W CLEAR 4.026 0.762 --- 3.066 102 1.313 2.954 112 0.963 NRCA3 F115W CLEAR 3.531 0.862 0.840 3.044 102 1.160 2.949 112 0.969 NRCA3 F150W CLEAR 2.632 0.878 0.852 2.310 102 1.139 2.204 112 0.954 NRCA3 F200W CLEAR 2.366 0.800 0.794 1.892 102 1.251 1.828 112 0.966 NRCA4 F090W CLEAR 3.839 0.753 --- 2.891 105 1.328 2.910 115 1.007 NRCA4 F115W CLEAR 3.366 0.813 0.784 2.738 105 1.229 2.776 115 1.014 NRCA4 F150W CLEAR 2.509 0.837 0.811 2.100 105 1.195 2.102 115 1.001 NRCA4 F200W CLEAR 2.256 0.791 0.778 1.785 105 1.264 1.805 115 1.012 NRCB1 F090W CLEAR 3.874 0.894 --- 3.463 108 1.119 3.564 118 1.029 NRCB1 F115W CLEAR 3.397 0.959 0.897 3.258 108 1.043 3.272 118 1.004 NRCB1 F150W CLEAR 2.532 0.946 0.906 2.394 108 1.058 2.412 118 1.008 NRCB1 F200W CLEAR 2.276 0.873 0.866 1.987 108 1.145 2.022 118 1.018 NRCB2 F090W CLEAR 4.009 0.842 --- 3.377 107 1.187 3.427 117 1.015 NRCB2 F115W CLEAR 3.515 0.897 0.870 3.154 107 1.114 3.128 117 0.992 NRCB2 F150W CLEAR 2.621 0.896 0.879 2.348 107 1.117 2.305 117 0.982 NRCB2 F200W CLEAR 2.356 0.829 0.847 1.953 107 1.206 1.952 117 0.999 NRCB3 F090W CLEAR 3.706 0.914 --- 3.386 103 1.095 3.425 113 1.012 NRCB3 F115W CLEAR 3.250 0.995 0.933 3.234 103 1.005 3.186 113 0.985 NRCB3 F150W CLEAR 2.423 0.986 0.936 2.388 103 1.015 2.352 113 0.985 NRCB3 F200W CLEAR 2.178 0.901 0.888 1.963 103 1.110 1.957 113 0.997 NRCB4 F090W CLEAR 3.769 0.818 --- 3.085 099 1.222 3.043 109 0.987 NRCB4 F115W CLEAR 3.305 0.831 0.811 2.746 099 1.204 2.698 109 0.983 NRCB4 F150W CLEAR 2.464 0.849 0.822 2.092 099 1.178 2.029 109 0.970 NRCB4 F200W CLEAR 2.215 0.812 0.795 1.799 099 1.231 1.771 109 0.985 NRCBLONG F277W CLEAR 0.422 1.000 --- 0.422 104 1.000 0.417 114 0.989 NRCALONG F277W CLEAR 0.433 1.107 --- 0.480 101 0.903 0.491 111 1.024 NRCBLONG F300M CLEAR 0.952 1.000 --- 0.952 104 1.000 0.949 114 0.997 NRCALONG F300M CLEAR 0.977 1.059 --- 1.035 101 0.944 1.013 111 0.979 NRCBLONG F356W CLEAR 0.372 1.000 --- 0.372 104 1.000 0.376 114 1.011 NRCALONG F356W CLEAR 0.381 1.088 --- 0.415 101 0.919 0.405 111 0.976 NRCBLONG F410M CLEAR 0.811 1.042 1.031 0.845 104 0.960 0.875 114 1.036 NRCALONG F410M CLEAR 0.832 1.031 1.031 0.858 101 0.970 0.870 111 1.015 NRCBLONG F444W CLEAR 0.335 1.096 1.031 0.367 104 0.912 0.373 114 1.015 NRCALONG F444W CLEAR 0.343 1.136 1.031 0.390 101 0.880 0.393 111 1.007 # # These are in 0989 but not in my own analysis NRCA1 F140M CLEAR 5.380 1.000 --- 5.380 106 1.000 5.075 116 0.943 NRCA1 F182M CLEAR 3.788 1.000 --- 3.788 106 1.000 3.490 116 0.921 NRCA1 F210M CLEAR 4.678 1.000 --- 4.678 106 1.000 4.404 116 0.941 NRCA1 F150W2 F162M 5.106 1.000 --- 5.106 106 1.000 4.663 116 0.913 NRCA2 F140M CLEAR 5.537 1.000 --- 5.537 100 1.000 5.355 110 0.967 NRCA2 F182M CLEAR 3.898 1.000 --- 3.898 100 1.000 3.779 110 0.970 NRCA2 F210M CLEAR 4.814 1.000 --- 4.814 100 1.000 4.841 110 1.006 NRCA2 F150W2 F162M 5.255 1.000 --- 5.255 100 1.000 5.007 110 0.953 NRCA3 F140M CLEAR 5.758 1.000 --- 5.758 102 1.000 5.011 112 0.870 NRCA3 F182M CLEAR 4.053 1.000 --- 4.053 102 1.000 3.375 112 0.833 NRCA3 F210M CLEAR 5.006 1.000 --- 5.006 102 1.000 4.235 112 0.846 NRCA3 F150W2 F162M 5.464 1.000 --- 5.464 102 1.000 4.516 112 0.827 NRCA4 F140M CLEAR 5.489 1.000 --- 5.489 105 1.000 4.714 115 0.859 NRCA4 F182M CLEAR 3.864 1.000 --- 3.864 105 1.000 3.328 115 0.861 NRCA4 F210M CLEAR 4.773 1.000 --- 4.773 105 1.000 4.223 115 0.885 NRCA4 F150W2 F162M 5.210 1.000 --- 5.210 105 1.000 4.371 115 0.839 NRCB1 F140M CLEAR 5.539 1.000 --- 5.539 108 1.000 5.441 118 0.982 NRCB1 F182M CLEAR 3.900 1.000 --- 3.900 108 1.000 3.776 118 0.968 NRCB1 F210M CLEAR 4.816 1.000 --- 4.816 108 1.000 4.760 118 0.988 NRCB1 F150W2 F162M 5.257 1.000 --- 5.257 108 1.000 5.068 118 0.964 NRCB2 F140M CLEAR 5.733 1.000 --- 5.733 107 1.000 5.196 117 0.906 NRCB2 F182M CLEAR 4.036 1.000 --- 4.036 107 1.000 3.592 117 0.890 NRCB2 F210M CLEAR 4.984 1.000 --- 4.984 107 1.000 4.517 117 0.906 NRCB2 F150W2 F162M 5.440 1.000 --- 5.440 107 1.000 4.804 117 0.883 NRCB3 F140M CLEAR 5.300 1.000 --- 5.300 103 1.000 5.324 113 1.005 NRCB3 F182M CLEAR 3.731 1.000 --- 3.731 103 1.000 3.627 113 0.972 NRCB3 F210M CLEAR 4.608 1.000 --- 4.608 103 1.000 4.562 113 0.990 NRCB3 F150W2 F162M 5.029 1.000 --- 5.029 103 1.000 4.891 113 0.973 NRCB4 F140M CLEAR 5.390 1.000 --- 5.390 099 1.000 4.557 109 0.846 NRCB4 F182M CLEAR 3.794 1.000 --- 3.794 099 1.000 3.268 109 0.861 NRCB4 F210M CLEAR 4.686 1.000 --- 4.686 099 1.000 4.137 109 0.883 NRCB4 F150W2 F162M 5.115 1.000 --- 5.115 099 1.000 4.269 109 0.835 NRCBLONG F250M CLEAR 1.632 1.000 --- 1.632 104 1.000 1.646 114 1.008 NRCALONG F250M CLEAR 1.673 1.000 --- 1.673 101 1.000 1.679 111 1.004 NRCBLONG F335M CLEAR 0.851 1.000 --- 0.851 104 1.000 0.851 114 1.000 NRCALONG F335M CLEAR 0.873 1.000 --- 0.873 101 1.000 0.989 111 1.133 NRCBLONG F360M CLEAR 0.870 1.000 --- 0.870 104 1.000 0.878 114 1.009 NRCALONG F360M CLEAR 0.892 1.000 --- 0.892 101 1.000 0.929 111 1.041 </code></pre>