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  1. Request For Comments
  2. RFC-322

Rename "*_flux" fields to "*_instFlux" in SourceCatalogs

    Details

    • Type: RFC
    • Status: Implemented
    • Resolution: Done
    • Component/s: DM
    • Labels:
      None

      Description

      Currently, the "flux" fields in our source catalogs are actually "on-chip, post-ISR counts", instead of "calibrated fluxes". This causes two problems: users looking for calibrated counts don't reach the correct objects, and we don't have a good place to put calibrated fluxes. I propose that all of our *Flux_flux/*Flux_fluxSigma fields be renamed *Flux_instFlux/*Flux_instFluxSigma, which will allow us to add e.g. *Flux_flux and *Flux_mag fields to our source catalogs to hold post-calibrated fluxes (in Maggies) and magnitudes (Pogson). The DPDD says in section 3.3 "Fluxes and Magnitudes" that we will distribute "flux" in units of "maggies", so this new naming is consistent with that.

      This developed while I was working on the new PhotoCalib object and I realized I'd inadvertantly overloaded the term "flux" in the code (sometimes meaning counts, sometimes calibrated flux). Some of this came from borrowing from the old Calib (where the term is very overloaded), and some from an attempt to get it right in the PhotoCalib code but then tripping over the input/output catalog field names.

      We will also rename the InstFlux slot to GaussianFlux, and remove the InstMag slot.

      In terms of work required, searching the stack (*.h, *.cc, *.py) found 111 matches in 33 files to Flux_flux, plus about 80 total matches in about 20 files (didn't compare overlap with the former) to several variations on + "_flux.

      In terms of timing, implementing this would wait until Calib was removed from the stack and replaced by PhotoCalib (not yet scheduled, but likely within the next couple months).

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            Hide
            jbosch Jim Bosch added a comment -

            Unless InstMag is something generated automatically from InstFlux, I'm not familiar with it.

            I have no idea what InstFlux was originally intended for. We've been abusing it as the slot we put GaussianFlux in for years.

            Show
            jbosch Jim Bosch added a comment - Unless InstMag is something generated automatically from InstFlux, I'm not familiar with it. I have no idea what InstFlux was originally intended for. We've been abusing it as the slot we put GaussianFlux in for years.
            Hide
            Parejkoj John Parejko added a comment -

            Simon Krughoff Your proposal seems reasonable. I'm not sure what your Flux_InstMag would represent; does anyone ever measure a "magnitude of counts" in that way?

            Also, we should be careful because the _flux that I'm proposing here is in Maggies (as our DPDD suggests), which is not quite a physical flux (there's an absolute calibration factor, which might just involve multiplying by 3631 Jy, but might also involve another small scale factor.

            Show
            Parejkoj John Parejko added a comment - Simon Krughoff Your proposal seems reasonable. I'm not sure what your Flux_InstMag would represent; does anyone ever measure a "magnitude of counts" in that way? Also, we should be careful because the _flux that I'm proposing here is in Maggies (as our DPDD suggests), which is not quite a physical flux (there's an absolute calibration factor, which might just involve multiplying by 3631 Jy , but might also involve another small scale factor.
            Hide
            krughoff Simon Krughoff added a comment -

            I suggested Flux_instMag because people seem to always want a magnitude, but I agree the "right" quantity to use is the fluxy one.

            Also, we should be careful because the _flux that I'm proposing here is in Maggies (as our DPDD suggests), which is not quite a physical flux (there's an absolute calibration factor, which might just involve multiplying by 3631 Jy, but might also involve another small scale factor.

            I specifically didn't mention a unit for the physical flux. Maggies is a physical flux unit in the sense that it is intended to represent the above atmosphere flux, it's just not Janskies. I do agree we need to be careful to be explicit about our convention for flux units.

            Show
            krughoff Simon Krughoff added a comment - I suggested Flux_instMag because people seem to always want a magnitude, but I agree the "right" quantity to use is the fluxy one. Also, we should be careful because the _flux that I'm proposing here is in Maggies (as our DPDD suggests), which is not quite a physical flux (there's an absolute calibration factor, which might just involve multiplying by 3631 Jy, but might also involve another small scale factor. I specifically didn't mention a unit for the physical flux. Maggies is a physical flux unit in the sense that it is intended to represent the above atmosphere flux, it's just not Janskies. I do agree we need to be careful to be explicit about our convention for flux units.
            Hide
            price Paul Price added a comment -

            I support Simon's proposal (if you remove the mention of counts) with Jim's addition.

            Show
            price Paul Price added a comment - I support Simon's proposal (if you remove the mention of counts ) with Jim's addition.
            Hide
            Parejkoj John Parejko added a comment -

            Thanks all.

            I've updated the Description with the final proposal, and filed DM-10302 as the implementation ticket.

            Show
            Parejkoj John Parejko added a comment - Thanks all. I've updated the Description with the final proposal, and filed DM-10302 as the implementation ticket.

              People

              • Assignee:
                Parejkoj John Parejko
                Reporter:
                Parejkoj John Parejko
                Watchers:
                Colin Slater, Gregory Dubois-Felsmann, Jim Bosch, John Parejko, John Swinbank, Kian-Tat Lim, Michael Wood-Vasey, Paul Price, Simon Krughoff, Tim Jenness
              • Votes:
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                Dates

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                  Updated:
                  Resolved:
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