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DC2018: the C29 caveat was wrong about where the convention residual lands #304

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jdeast merged 1 commit into from
Sep 17, 2026
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DC2018: the C29 caveat was wrong about where the convention residual lands #304

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64 changes: 38 additions & 26 deletions examples/DC2018/dc18_truth_table.py
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Original file line number Diff line number Diff line change
Expand Up @@ -596,52 +596,64 @@ def print_convention_caveat(rows):
rather than only in the paper because this table IS that discussion for
anyone reading a scoring run, and a caveat that lives somewhere else is a
caveat nobody applies.

REWRITTEN 2026-09-17 AFTER THE MEASUREMENT CONTRADICTED THE FIRST VERSION.
That version said theta_star is biased low by 10**(-0.2*grey) -- 0.766x on
event 194 -- straight from the CSB relation. The ab194/av_true arm, the
first run with the colour-anchored prior, measured theta_star at 0.983x of
truth. So the arithmetic was right about the CSB relation and wrong about
where the residual lands: theta_star is PROTECTED, because the light curve
pins rho * theta_E independently of the SED. What actually absorbs the
grey term is teffsed, and behind it the (R_source, D_source) pair.
"""
seen = [r["event"] for r in rows if str(r["event"]) in C29_GREY]
if not seen:
return
print("\n" + "=" * 104)
print("CAVEAT: theta_star (hence theta_E, hence lens mass) IS BIASED LOW")
print(" AGAINST THIS ANSWER KEY, BY CONSTRUCTION AND NOT BY ERROR.")
print(
" This simulation reddened MONOCHROMATICALLY at each filter's effective"
)
print(
" wavelength; we integrate a reddened spectrum through the passband,"
"CAVEAT: THE SIMULATION'S EXTINCTION CONVENTION IS NOT OURS, AND THE"
)
print(" RESIDUAL LANDS ON teffsed AND (R_source, D_source).")
print(" This simulation reddened MONOCHROMATICALLY at each filter's")
print(
" which is what a measurement is. For a filter as wide as W149 those"
" effective wavelength; we integrate a reddened spectrum through the"
)
print(
" differ, so no single av reproduces both simulated band extinctions in"
" passband, which is what a measurement is. For a filter as wide as"
)
print(
" our model. We anchor the colour, which leaves a GREY residual, and a"
" W149 those differ, so no single av reproduces both simulated band"
)
print(" grey error moves only the -0.2*W149_0 term of the CSB relation:")
print(" %-7s %-12s %s" % ("event", "grey (mag)", "theta_star bias"))
print(" extinctions in our model. Anchoring the colour leaves a GREY")
print(" residual in both bands:")
print(" %-7s %s" % ("event", "grey (mag)"))
for ev in sorted({str(e) for e in seen}):
g = C29_GREY[ev]
print(" %-7s %+12.2f %14.3fx" % (ev, g, 10 ** (-0.2 * -g)))
print(
" On event 194 that is 56% of the measured deficit (fit/truth = 0.62x,"
)
print(
" -0.208 dex, of which -0.116 is this). The rest is OURS and is not"
)
print(" %-7s %+10.2f" % (ev, C29_GREY[ev]))
print(" MEASURED ON av_true (event 194, prior av = 9.01 +/- 0.3, ptde,")
print(" Rhat 1.00, ESS 23-25k, 78/78 chains):")
print(" theta_star 0.983x truth <-- NOT biased; the light curve")
print(" pins rho * theta_E")
print(" R_source 0.403x truth pull -5.25")
print(" D_source 0.410x truth pull -5.35")
print(" theta_E 0.774x truth pull -0.66 (within 1 sigma)")
print(" R and D slide ~2.45x IN LOCKSTEP, which is why their ratio --")
print(" theta_star -- survives while each is individually -5 sigma. The")
print(
" explained by it. The sweep's av prior carries this spread in its"
" flux the grey term over-predicts is absorbed by a source made too"
)
print(
" WIDTH, which does not remove the bias -- nothing in the fit can --"
" COOL (teffsed 3040 K here), and the distance follows the resulting"
)
print(" but keeps it from masquerading as a measurement. The zeropoints")
print(" luminosity inward.")
print(" DO NOT read the -5 sigma R_source/D_source pulls as 'the")
print(" convention explains them': that is not established. What IS")
print(
" are deliberately NOT widened: with `filters: []` they are the only"
" established is that the colour-anchored prior moved theta_star from"
)
print(" colour information in the fit, and slackening them would trade")
print(" teffsed away for an honest error bar. None of this applies to")
print(" real Roman data, where the integrated treatment is correct.")
print(" 0.62x truth (the old arms, av ~ 4.25 from A_W149) to 0.983x, and")
print(" R_source's pull from -13.10 to -5.25. The remainder is OURS.")
print(" None of this applies to real Roman data, where the integrated")
print(" treatment is simply the correct one.")


def main():
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