ACT (AdvACT) Data Products - DR6 SZ Cluster Catalogs

Change log

v1.0

  • Used Nemo v0.9.0
  • Fixed regression; warnings column was missing some systems flagged in DR5 as possibly projected.
  • Fixed regression; notes column was missing some entries from DR5 that are still valid.
  • Redshifts have been changed for 6 clusters by | Δz | > 0.02. The biggest mover is ACT-CL J1414.0+0841 from z = 0.08 to z = 2.0 following further inspection; this is a low S/N detection and marked as a 'Possible projected system' in the warnings column, so use with caution.
  • MACS J0242.6-2132, discussed as a non-detection in v0.11/arXiv v2 is now detected (ACT-CL J0242.6-2132), despite the bright central point source (but is flagged, so use with caution).

Known issues

  • Many objects do not have optical coords (e.g. BCG location) - for many objects opt_RADeg, opt_decDeg = 0, 0.

Available data products

The following data products are made available with this release:


Cluster Catalog

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).

Legacy cluster sample

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:

  • fixed_SNR > 5.5
  • flags == 0
  • footprint_Legacy == True

Catalog of multiple systems (cluster pairs and potential superclusters)


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 ACT Collaboration (2025). 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.
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.

Other data products produced with Nemo

The file DR6_nemo-products_v1.0.tgz is a tarball containing all of the data products produced by Nemo. This includes:

  • YAML config file used for the Nemo run
  • Cluster candidates list
  • Filtered maps: one in units of signal-to-noise, and one in units of Comptonization parameter (× 10-4) at the reference filter scale
  • Point source catalogs: one per ACT frequency band (f090, f150, f220)
  • Selection function files: masks, Q functions, noise tables and maps, for various footprints
  • Cluster signal model maps: One map per ACT frequency band (f090, f150, f220; units are ΔT (CMB) in μK) - they can be directly subtracted from the ACT frequency maps to mitigate the tSZ signal from clusters

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.

Random catalogs

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.

Information on this page was taken from this site.

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