Euclid × CMB Lensing

Cail Daley & Euclid CMBX team

SPT Secondaries and Cross-Correlations Call

March 30, 2026

Euclid DR1 targets October 2026,
but this will be extremely challenging

• ESA hack, B-modes under investigation, unprecedented turnaround

• The CMBX group in Paris meets for full-day hacks once a week:

  • Cail Daley, Léa Dumilly, Margherita Lembo, Emma Ayçoberry, Vilasini Tinnaneri Sreekanth, Laura Salvati, Giulio Fabbian

• Building a pipeline for Euclid × CMB lensing and tSZ

• We haven’t used SPT \(y\)-maps yet — Abhi’s maps for DR1?

• Giulio talked to someone at NERSC while in Santa Barbara: should be no problem to reserve 10s of GBs for at least the Euclid catalogs

• Making progress but still waiting on a form to give SPT collaborators data access. Sorry!

Euclid RR2 is unblinded — we’re building a full pipeline while we can still poke around

• ~30% of DR1 area (385 deg²), unblinded

• Cross-correlating with \(\kappa\) from ACT DR6 and SPT-3G winter field

• Two tracers: \(\delta_g \kappa\) and \(\gamma \kappa\), 6 tomographic bins

• Pseudo-\(C_\ell\) estimation with NaMaster, Gaussian covariance

::: {style=“font-size:0.72em;text-align:right;margin-top:-35px;margin-right:60px”} Credit: M. Lembo

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Six tomographic bins

• WL: ~50M galaxies, two shear pipelines (lensmc, metacal)

• GC: ~30M galaxies, 6 bins to \(z \sim 0.9\)

Galaxy density × CMB lensing (\(\delta_g \kappa\))

Cosmic shear × CMB lensing (\(\gamma \kappa\))

tSZ × galaxy clustering with Planck (Léa)

Map vs catalog estimator agree at high \(\ell\), diverge at low \(\ell\)

Eleven VMPZ-ID systematic maps track observational effects

Some signs of systematic contamination

\(X_\ell^f = \ell \, C_\ell^{\kappa S} C_\ell^{fS} / C_\ell^{SS}\) where \(f\) = galaxy field, \(S\) = systematic map

\(\ell\)-dependence