Every galaxy is noisy
Its original shape is unknown. One stretched galaxy proves nothing, so astronomers compare many galaxy pairs.
KiDS-1000 · observed galaxy shapes · 1006 deg²
Dark matter leaves fingerprints on galaxy shapes.
They are too small to trust galaxy by galaxy. This laboratory shows how KiDS combined noisy shapes into a measurable correlation—and why looking farther into the Universe strengthens the signal.
Read the real measurementThree ideas before the graph
What are we actually measuring?
ξ+ measures agreement
Positive ξ+ means nearby galaxy shapes share a preferred alignment more often than random orientations would produce.
Tomography adds depth
KiDS divides sources into five redshift bins. Higher bins look through more intervening structure and usually accumulate more lensing.
Real KiDS-1000 ξ+ vector
Compare three lines of sight through cosmic history.
Choose a bin pair. Every dot, uncertainty bar and covariance calculation below comes from the official KiDS-1000 FITS release.
Observed correlation
Nearby sources: bins 1 × 1
KiDS-1000 ξ+1σ marginal uncertaintyHorizontal axis is logarithmic
Where are the source galaxies?
Released redshift distributions n(z)
Read the experiment
Longer light paths sample more structure.
Inspect the nine measured values
| θ (arcmin) | ξ+ | 1σ uncertainty | ξ+/σ |
|---|
Research boundary
What this laboratory does—and does not do.
Directly observed here
Fifteen ξ+ tomographic vectors, their angular bins, the released covariance blocks and the five KiDS source-redshift distributions.
Calculated here
A transparent χ² test of ξ+ = 0 for one selected bin pair. The complete covariance block is used; points are not treated as independent.
Not claimed here
No S8 posterior, cosmological fit, intrinsic-alignment inference or baryonic-feedback constraint. Those require the full likelihood and theory pipeline.
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