EDF-S Lensing



Cail Daley, Srini Raghunathan, Julien Carron

SPT Face-to-Face Meeting

July 3, 2025

Outline

  • Background on Euclid Q1 and EDF-S

  • EDF-S CMB lensing motivation

  • Current status of lensing analysis

  • Next steps & timeline

Euclid Q1 & EDF-S

  • Euclid’s “Quick Data Release 1” (Q1) is the first public data from Euclid, and includes 3 fields (EDF-S, EDF-F, EDF-N) totaling 63 deg².

    • More observations will be conducted to turn the Q1 fields in Deep Fields (50x deeper than the Wide Survey) for legacy science.

  • SPT observed EDF-S last fall, and did a data release of catalogs, temperature maps, and associated data products at the beginning of June.

CMB Lensing with EDF-S

  • EDF-S will become a legacy deep field, and CMB lensing lensing maps will be a useful data product for the community.

  • While Q1 data was nominally not intended for cosmology, the galaxy clustering signal is very strong. Giulio Fabbian has been leading a 2x2pt galaxy clustering \(\ev{\delta_g\delta_g}\) & CMB lensing \(\ev{\delta_g \kappa_{\rm CMB}}\) analysis with ACT and Planck lensing maps.

  • The ACT cross-correlation SNR is about 6—we can do much better with SPT!

Mapmaking & Analysis

  • cosmo-v1 map run started in December thanks to the DPCs
  • Similar mapmaking settings to 2-year winter maps.
  • Noise realizations, mocks, and source templates produced by Srini.
  • Since the field is small, working at 0.5’ resolution.



Analysis wiki: https://pole.uchicago.edu/spt3g/index.php/EDFS_Lensing

Source Templates

  • Using a higher mapmaking threshold of 20 mJy in combination with a source template to reduce number of holes in the map and filtering artifacts.

    • Source template: mock-observed map of beam-convoled sources made from the EDF-S source catalog.

  • Sources > 20 mJy and clusters will still be inpainted.

  • Only sources > 6 mJy are included in the template, to match the foreground power in the 2-year Gaussian lensing sims.

  • This approach has required several iterations, but seems to be working well.

Source Templates

Source Templates

Component Separation

Leverage frequency-dependence of noise and foregrounds to make
a cleaner estimate of the CMB: \[X_{\vbell}^{\rm MV} = \sum_{i} \mathbb W_{\vbell}^{i} X_{\vbell}^{i}.\]

The Noise Line

  • Apparent feature around \(\ell\) ~ 600 in BB; doesn’t show up in signflips so seems to be stable across observations, but averages down in ILC?

  • Easy to mask, but this seems to be a new feature in the mapmaker (also present in 2-yr winter \(\tau\)-decon) that we may want to understand for e.g. 5-yr winter maps.

Lensing Reconstruction

  • Adapting pipeline from the 2-year winter flat-sky QE analysis.

  • So far only running on data; so no mean-field, Monte-Carlo response, etc.

Cross-correlations with Euclid

  • Galaxy density maps and ACT bandpowers kindly provided by Giulio.
  • Error bars calculated with NaMaster.

Summary & Next Steps

  • Data processing aspects largely wrapped up.
  • Lensing maps maps look sensible but amplitude seems to be 40-50% low.
  • Cross-correlation with Euclid is already higher-SNR than ACT (6.8 vs 8.2),
    and will improve after maps are properly normalized.
  • Next steps:
    • Run on sims to get response, mean-field, and noise bias corrections.
      \(\implies\) some level of lensing power spectrum validation.
    • Map calibration (Pcal, T\(\to\)P, EB nulling…)
    • Try Julien’s lensing reconstruction code

Timeline & Euclid DR1

  • Planning to have a draft in the fall.

  • One paper on lensing maps and x-corr? Or two separate ones?

  • Euclid RR2 (preview of DR1) is here and cross-correlations with ACT have begun.

  • Margherita Lembo & I have submitted a EC/MoU proposal for a Euclid-SPT
    3 \(\times\) 2pt (\(\delta_g \kappa, \gamma \kappa, \delta_g \gamma\)) project. Let me know if you’re interested in joining!

Credit: Margherita Lembo

Thanks!