Subaru weak lensing measurement of a z = 0.81 cluster discovered by the Atacama Cosmology Telescope Survey★
Bibliographic record
Abstract
We present a Subaru weak lensing measurement of ACT-CL J0022.2−0036, one of the most luminous, high-redshift (z = 0.81) Sunyaev–Zel'dovich (SZ) clusters discovered in the 268 deg2 equatorial region survey of the Atacama Cosmology Telescope that overlaps with Sloan Digital Sky Survey (SDSS) Stripe 82 field. Ours is the first weak lensing study with Subaru at such high redshifts. For the weak lensing analysis using i′-band images, we use a model-fitting (Gauss–Laguerre shapelet) method to measure shapes of galaxy images, where we fit galaxy images in different exposures simultaneously to obtain best-fitting ellipticities taking into account the different point spread functions (PSFs) in each exposure. We also take into account the astrometric distortion effect on galaxy images by performing the model fitting in the world coordinate system. To select background galaxies behind the cluster at z = 0.81, we use photometric redshift estimates for every galaxy derived from the co-added images of multi-passband Br′i′z′Y, with PSF matching/homogenization. After a photometric redshift cut for background galaxy selection, we detect the tangential weak lensing distortion signal with a total signal-to-noise ratio of about 3.7. By fitting a Navarro–Frenk–White model to the measured shear profile, we find the cluster mass to be |$M_{200\bar{\rho }_{\rm m}} = [7.5^{+3.2}_{-2.8}({\rm stat.})^{+1.3}_{-0.6}({\rm sys.})]\times 10^{14} \,\mathrm{M}_{\odot }\,h^{-1}$|. The weak lensing-derived mass is consistent with previous mass estimates based on the SZ observation, with assumptions of hydrostatic equilibrium and virial theorem, as well as with scaling relations between SZ signal and mass derived from weak lensing, X-ray and velocity dispersion, within the measurement errors. We also show that the existence of ACT-CL J0022.2−0036 at z = 0.81 is consistent with the cluster abundance prediction of the Λ-dominated cold dark matter structure formation model. We thus demonstrate the capability of Subaru-type ground-based images for studying weak lensing of high-redshift clusters.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".