This is a public release version of the data products associated with the ACT DR6 cluster catalog paper (Aguena et al. 2026).
Please contact Matt Hilton with any questions, comments, or suggestions.
Based on Nemo output: DR6ClusterSearch (version used: v0.9.0)
See here for information on how to reproduce most of the data products listed on this page.
v1.0
v0.11
v0.10
The following data products are made available with this release:
The file DR6_cluster-catalog_v1.0.fits is a FITS table that contains the catalog of ACT SZ-selected and optically confirmed clusters with redshifts. It can be viewed with any compatible viewer, e.g., TopCat, or read into Python using the astropy.table module.
The table columns contain the following information:
| Column | Description |
|---|---|
| name | Cluster name in the format ACT-CL JHHMM.m±DDMM. |
| RADeg | Right Ascension in decimal degrees (J2000) of the SZ detection by ACT. |
| decDeg | Declination in decimal degrees (J2000) of the SZ detection by ACT. |
| SNR | Signal-to-noise ratio, optimized over all filter scales (in H21, the symbol SNR was used for this quantity). |
| y_c | Central Comptonization parameter (× 10-4) measured using the optimal matched filter template (i.e., the one that maximizes detection S/N q). Note that inferred\_y\_c provides a lower scatter estimate of this quantity. Uncertainty column(s): err_y_c. |
| fixed_SNR | Signal-to-noise ratio at the reference 2.4′ filter scale (in H21, the symbol SNR2.4 was used for this quantity). This is the quantity used for estimating completeness. |
| fixed_y_c | Central Comptonization parameter (× 10-4) measured at the reference filter scale (2.4′). This is the SZ signal used for inferring mass estimates and estimating mass completeness limits. Uncertainty column(s): fixed_err_y_c. |
| template | Name of the matched filter template resulting in the highest S/N (q) detection of this cluster. |
| tileName | Name of the ACT map tile in which the cluster was found. |
| flags | Number of times a location on the sky was flagged, for whatever reason. Use flags = 0 to select `clean' regions. Note that many regions are flagged due to the presence of bright stars (which make obtaining photometric redshifts difficult or impossible), and the flagging set-up used for ACT DR6 is conservative. |
| finderFlag | Number of times a location on the sky was flagged during cluster finding. A non-zero value for this quantity indicates that a point source was subtracted at this location. As the point source subtraction process is not perfect, objects with this flag should be treated with care. |
| starFlag | If non-zero, indicates an area of sky close to a bright star. While this should not affect detection of the SZ signal, it may make it difficult or impossible to obtain a redshift estimate for this object. |
| extObjFlag | If non-zero, indicates an area of sky associated with an extended foreground object, such as a galaxy or a nebula. |
| dustFlag | If non-zero, indicates an area of sky that is dusty, as traced by emission in the \textitPlanck 353 GHz map. |
| ringFlag | If non-zero, indicates an object flagged as a possible ring artifact. It may be that the object is in fact a cluster. If so, the SZ signal may have been artificially boosted by the presence of the ring, so use these objects with care. |
| redshift | Adopted redshift for the cluster. The uncertainty is only given for photometric redshifts. Uncertainty column(s): redshiftErr. |
| redshiftType | Redshift type (spec = spectroscopic, phot = photometric). |
| redshiftSource | Source of the adopted redshift. |
| M500c | M500 with respect to the critical density, in units of 1014M⊙. This assumes a scaling relation normalization 10A_0= 3.0 × 10-5, which is consistent with recent weak-lensing measurements (Robertson et al. 2024, Shirasaki et al. 2024). Uncertainty column(s): M500c_errPlus, M500c_errMinus. |
| M200c | M200 with respect to the critical density, in units of 1014M⊙, converted from M500c using the Bhattacharya et al. (2013) c-M relation. Uncertainty column(s): M200c_errMinus, M200c_errPlus. |
| M200m | M200 with respect to the mean density, in units of 1014M⊙, converted from M500c using the Bhattacharya et al. (2013) c-M relation. Uncertainty column(s): M200m_errPlus, M200m_errMinus. |
| M500cUncorr | M500c in units of 1014M⊙, uncorrected for bias due to the steepness of the cluster mass function. Uncertainty column(s): M500cUncorr_errPlus, M500cUncorr_errMinus. |
| A10_M500c | M500csup>A10 in units of 1014M⊙, assuming the Arnaud et al. (2010) scaling relation (this was the default assumption in previous ACT data releases). Uncertainty column(s): A10_M500c_errPlus, A10_M500c_errMinus. |
| A10_M200c | M200 with respect to the critical density, in units of 1014M⊙, converted from M500csup>A10 using the Bhattacharya et al. (2013) c-M relation. Uncertainty column(s): A10_M200c_errMinus, A10_M200c_errPlus. |
| A10_M200m | M200 with respect to the mean density, in units of 1014M⊙, converted from M500cA10 using the Bhattacharya et al. (2013) c-M relation. Uncertainty column(s): A10_M200m_errMinus, A10_M200m_errPlus. |
| A10_M500cUncorr | M500csup>A10 in units of 1014M⊙, assuming the Arnaud et al. (2010) scaling relation (this was the default assumption in previous ACT data releases), but neglecting the Eddington bias correction. This is the mass estimate to use if you wish to compare with the \textitPlanck PSZ2 catalog. Uncertainty column(s): A10_M500cUncorr_errMinus, A10_M500cUncorr_errPlus. |
| theta500Arcmin | Inferred value for the angular size θ500c (arcmin), using the scaling relation model. Uncertainty column(s): theta500Arcmin_err. |
| Q | Value of the filter mismatch function inferred for this cluster. Uncertainty column(s): Q_err. |
| inferred_y_c | Inferred value for the central Comptonization parameter y_0 (× 10-4), using the scaling relation model. Uncertainty column(s): inferred_y_c_err. |
| inferred_Y500Arcmin2 | Inferred value for the integrated Comptonization parameter Y500c (arcmin^2). Note that this is a model dependent quantity which depends on the assumed pressure profile and scaling relation parameters, and is not more physically meaningful than using M500c directly. Uncertainty column(s): inferred_Y500Arcmin2_err. |
| footprint_DES | Flag indicating if the cluster falls within the Dark Energy Survey (DES) footprint. |
| footprint_HSC | Flag indicating if the cluster falls within the Hyper Suprime-Cam Subaru Strategic Program (HSC) footprint. |
| footprint_KiDS | Flag indicating if the cluster falls within the Kilo Degree Survey (KiDS) footprint. |
| footprint_eROSITADe | Flag indicating if the cluster falls within the SRG/eROSITA All Sky Survey (eRASS1 Western Galactic hemisphere) footprint. |
| footprint_Legacy | Flag indicating if the cluster falls within the ACT Legacy footprint. |
| zCluster_delta | Density contrast statistic measured at the zCluster photometric redshift. Uncertainty column(s): zCluster_errDelta. |
| zCluster_source | Photometry used for zCluster measurements. One of: DECaLS (DR10), KiDS (DR4), SDSS (DR16), PS1 (DR2). |
| RM | Flag indicating cross-match with a redMaPPer-detected cluster in the SDSS footprint (Rykoff et al. 2014). |
| eRASS1CL | Flag indicating cross-match with an eRASS1 cluster (Bulbul et al. 2024). |
| RMDESY6 | Flag indicating cross-match with a redMaPPer-detected cluster in the DES Y6 footprint (Rykoff et al. 2016). |
| WaZP | Flag indicating cross-match with a WaZP-detected cluster in the DES Y6 footprint (Benoist et al. 2025). |
| CAMIRA | Flag indicating cross-match with a CAMIRA-detected cluster in the S23B catalog (Oguri et al. 2018, Oguri et al. in prep.). |
| MaDCoWS2DR2 | Flag indicating cross-match with a MaDCoWS DR2 cluster (Thongkham et al. 2024). |
| opt_RADeg | Alternative optically-determined Right Ascension in decimal degrees (J2000), from a heterogeneous collection of measurements (see opt\_positionSource). |
| opt_decDeg | Alternative optically-determined Declination in decimal degrees (J2000), from a heterogeneous collection of measurements (see opt\_positionSource). |
| opt_positionSource | Indicates the source of the alternative optically-determined cluster position. CAMIRA (position from the CAMIRA cluster finder; Oguri et al. 2018, Oguri et al., in prep.), MADCOWS2DR2 (position from MaDCoWS2 DR2; Thongkham et al. 2024), RM, RMDESY3, RMDESY6, RMDESY6ACT (position from the redMaPPer cluster finder, in SDSS, DES Y3 or Y6; Rykoff et al. 2014, 2016), Vis-BCG (BCG position from visual inspection of available optical/IR imaging; this work and H21), WaZP (position from the WaZP cluster finder in DES Y6; Benoist et al. 2025), WH2015 (position from Wen & Han 2015), WH2022 (position from Wen & Han 2022), WH2024 (position from Wen & Han 2024). |
| notes | If present, at least one of: AGN? (central galaxy may have color or spectrum indicating it may host an AGN); Lensing? (cluster may show strong gravitational lensing features); Merger? (cluster may be a merger); Star formation? (a galaxy near the center may have blue colors which might indicate star formation if it is not a line-of-sight projection). These notes are not comprehensive and merely indicate some systems that were identified as potentially interesting during visual inspection of the available optical/IR imaging. |
| warnings | If present, a warning message related to the redshift measurement for this cluster (e.g., Possible projected system). |
The file DR6_cluster-legacy-catalog_v1.0.fits is a FITS table that contains the ACT legacy cluster subsample, which is suggested for use in cosmological analyses. It contains exactly the same information as the full cluster catalog, but with the following cuts pre-applied:
The file DR6_multiple-systems_v1.0.fits is a FITS table that contains the catalog of multiple systems and potential superclusters, assembled as described in Aguena et al. (2026). It can be viewed with any compatible viewer, e.g., TopCat, or read into Python using the astropy.table module.
The table columns contain the following information:
| Column | Description |
|---|---|
| name | Name of the multiple system; constructed from the names of the individual clusters as given in the cluster catalog. |
| meanRADeg | Mean Right Ascension in decimal degrees (J2000) of the clusters forming the multiple system. |
| meanDecDeg | Mean Declination in decimal degrees (J2000) of the clusters forming the multiple system. |
| meanRedshift | Mean of the redshifts of the individual clusters that make up the multiple system. |
| numClusters | The number of clusters that make up the multiple system. |
| maxSeparationMpc | The projected distance in Mpc (at the median redshift) between the two most widely separated components of the multiple system. |
| maxSeparationArcmin | The angular separation in arcmin between the two most widely separated components of the multiple system. |
| includesPhotoRedshift | Flag indicating that the multiple system includes at least one cluster that has only a photometric redshift estimate. |
| tileName | Name(s) of the ACT map tile(s) (typically with dimensions 25 × 2 deg) in which each component of the multiple system was found. |
The file DR6_nemo-products_v1.0.tgz is a tarball containing all of the data products produced by Nemo. This includes:
See here for more information on the outputs listed above.
To perform forced photometry and obtain SZ mass estimates of other catalogs (e.g. eRASS1 clusters) in the ACT DR6 maps, after extracting the archive, you can run something like, e.g.,
nemoMass DR6ClusterSearch.yml -c erass1cl_primary_v3.2.fits -F.
The file DR6_randoms_v1.0.tgz is a tarball containing random catalogs generated using the nemoMock command.
Please contact Matt Hilton with any questions or comments.