Mission Overview

Physics at High Angular resolution in Nearby GalaxieS - Catalogs (PHANGS-CAT)

Primary Investigator: Janice C. Lee

HLSP Authors:  David Thilker, Bradley Whitmore, Janice C. Lee, Sinan Deger, Daniel Maschman, Kirsten Larson, Stephen Hannon, Aida Wofford, James Lilly, Jordan Turner, Kiana Henny, Hamid Hassani 

Released: 2022-02-08

Updated: 2026-06-08

Primary Reference(s): Lee et al. 2022Additional References

DOI: 10.17909/jray-9798

Citations: See ADS Statistics

Read Mes:

 

Slideshow

Now showing slide 1 of 19

Examples of HST, MUSE, and ALMA images

Lee 2022 - A grid of images showing the primary components of PHANGS-HST: MUSE, ALMA, HST. The bottom row contains images from HST and ALMA of a face-on spiral galaxy. The top row shows “zoom-ins” on clusters and compact association regions within that galaxy from MUSE and ALMA.

Examples of HST, MUSE, and ALMA images - multi-scale associations - and cluster and compact associations from Lee et al. 2022 – Fig. 9.

NGC 1566 Star Clusters

Thilker 2022 - Locations of star clusters in the spiral galaxy NGC 1566, where each point is colored by cluster age. The youngest clusters (blue) are mainly found in the spiral arms.

Location of class 1 and class 2 machine learning classified clusters in NGC 1566 from Thilker et al. 2022 – Fig. A4. 

Evolutionary tracks

Deger 2022 - Plots of the U-B vs V-I (top), and NUV - B vs V-I (bottom) diagrams are shown with evolutionary tracks for several metallicities and star formation models superposed. The reddening vector is included to show the effects on the photometric observations (grey points)

Evolutionary tracks in color-color diagrams compared to photometry for class 1/2/3 clusters from  Deger et al. 2022 –Fig. 20.

Cluster Classes

Wei et al. 2020 - Four rows of snapshots are shown with examples of class 1 (symmetric - top row), class 2 (asymmetric- second row), class 3 (compact associations - third row), class 4 - (artifacts - bottom row).  The far left panel shows a large field of view and a color image using the BVI bands while the second panel shows a blowup of the same image. The rest of the rows show the image in increasingly redder filters (F275W = NUV, F336W = U, F438W = B, F555W = V, F814W = I).

Illustration of the four cluster classes from Wei et al. 2020 – Fig. 1. 

Color-color diagrams

Whitmore et al. 2021 - Four U-B vs V-I diagrams are shown for the class 1 and 2 objects in the  galaxy NGC 1566. The top left panel shows the distribution of points from the PHANGS study; the upper right panel shows the distribution from the LEGUS study, the bottom left panel shows the distribution using the RESNET machine learning classifications, and the bottom right shows the distribution using the VGG machine learning classifications. The distributions all look similar, demonstrating that the various classifications are compatible with each other.

Demonstration that similar color-color diagrams are obtained using PHANGS, LEGUS, and machine learning classifications from Whitmore et al. 2021 – Fig. 9. 

Cluster Classification

Hannon et al. 2023 - Four panels showing what are called confusion matrices. These  are comparisons of the agreement in classifications of star clusters from the PHANGS and LEGUS projects for class 1 (symmetric), class 2 (asymmetric), class 3 (compact associations) and class 4 - (artifacts). The fact that the best agreement (darker colors) are generally along the diagonal  (i.e., where the two methods end up with the same classification) shows that the agreement is relatively good, typically ranging in the 50 - 80 % range.

Cluster classification confusion matrices for LEGUS and PHANGS catalogs from  Hannon et al. 2023 – Fig. 2.

PHANGS Spectral Energy Distribution (SED) Fitting

Turner et al. 2021 - Three rows showing the Spectral Energy Distributions (SEDs) on the left, and color images of three clusters on the right. This shows how we determine physical parameters of age, mass, and reddening from the HST photometry using a program called CIGALE. Color snapshots of the objects on the right show that young clusters are blue (e.g., the top cluster is assigned an age of 1 Myr), while old clusters are reddish (e.g., the bottom cluster is assigned an age of 1.3 Gyr).

Spectral Energy Distribution (SED) fitting of PHANGS HST data using  CIGALE from Turner et al. 2021 – Fig.  6. 

Globular Cluster Ages

Whitmore et al. 2023 - A U-B vs V-I color-color diagram is shown on the left with evolutionary models and photometric data points for class 1, 2 and 3. objects. A E((B-V) reddening vs age diagram is shown on the right with the same data points. This demonstrates how clusters in certain locations in a color-color diagram have severe age/reddening/metallicity degeneracies. This results in old globular clusters (ages around 10 Gyr) mistakenly being given ages  around 5 Myr (blue ovals), ~200 Myr (green ovals), or 2 Gyr (red ovals) in most cases.

Illustration of how the age/reddening/metallicity degeneracy can lead to 'catastrophic' errors in age dating old globular clusters from Whitmore et al. 2023 – Fig. 3.

NGC 1566 Multi-scale associations

Larson et al. 2023 - A black and white image of a star forming region with the 16 pc, 32 pc, and 64 pc multi-scale associations shown by the blue (smallest regions), purple and orange (largest regions) contours respectively.

Multi-scale associations in NGC 1566 using 16 pc (blue), 32 pc (purple), and 64 pc (orange)  scales from Larson et al. 2023 – Fig. 4. 

Clusters and Associations

Maschmann 2024 - A 3 X 3 grid of color-color diagrams for class 1 (left) class 2 (middle) and class 3 (right) clusters and compact associations. The upper rows are for a NUV-B vs V-I diagram, the middle row is for a U-B vs V-I diagram; the bottom row is for a B-V vs V-I diagram. This shows how the distributions of star clusters in color-color diagrams can be roughly divided into the Young Cluster Locus (YCL), Middle-Age Plume (MAP), and Old Globular Cluster Clump (OGCC).

Distributions of star clusters and compact associations in color-color diagrams from Maschmann et al. 2024 Fig. 6. 

Number of Clusters

Floyd et al. 2024 - A histogram showing the number of globular cluster candidates  (blue) and contaminants (orange)  in the 17 galaxies in the sample. The left bar in each pair is for the human classified clusters while the right bar in each pair is for the machine learning classified clusters.  Typical values are around 100 globular clusters per galaxy.

Number of old globular clusters and potential contaminants for both human classified and machine learning classified objects from Floyd et al. 2024 Fig. 6. 

Age-mass diagram

Thilker et al. 2025 - A plot of the log of the galaxy mass vs the log of the star formation rate (i.e., the Main Sequence of star forming galaxies) for the 38 galaxies in the sample. Small version of the cluster age-mass diagrams are shown as the data points.

Demonstration of how the age-mass diagrams of star clusters correlate with the galaxies position in the Main Sequence of star-forming galaxies from Thilker et al. 2025 – Fig. 27.

PHANGS JWST Filters

Lee et al. 2023 - The top panel shows model Spectral Energy Distributions (SEDs) for different age and reddening over a range encompassing both HST and JWST observations. The bottom row shows a similar figure over just the JWST part of the spectrum, i.e., from the F200W to the F2100W filter.

Filters used for the PHANGS-JWST Cycle 1 observations and model SEDs as a function of age and reddening from Lee et al. 2023 - Fig. 2.

21 micron correlation

Hassani et al. 2023 - A plot of the 21 micron luminosity density vs. the Halpha luminosity as a function of cluster age from 2.5 Myr (blue) to 25 Myr (orange). The size of the symbol is proportional to the mass, from 10^2 (small) to 10^4 (large) solar mass.

Correlation between 21 micron luminosity density and Halpha luminosity as a function of star cluster age from Hassani et al. 2023 - Fig. 5.

Empical SED templates

Whitmore et al. 2025 - The U-B vs V-I color-color diagram showing the location of five "degeneracy-free" regions, where uncertainties in reddening do not lead to uncertainties in age. The black line shows a solar metallicity Bruzual-Charlot 2003 model used to age-date the clusters. The large black points show the clusters with strong F770W PAH emission. The small snapshots shows that all but 1 of the 40 strong PAH emitters has strong Halpha, and is consistent with an age less than 5 Myr.

Locations of "degeneracy-free" regions in color-color diagram used to develop empirical SED (HST+JWST) templates from Whitmore et al. 2025 - Fig. 3.

Spectral Energy Distributions

Henny et al. 2025 - Three rows of figures for three representative star clusters showing the SEDs (spectral energy distribution) on the left with snapshot images using different filters above them; a U-B vs V-I diagram in the middle; and a color image on the right using the F658N (Halpha), F335M (NIRCAM), and F435W (B-band).

Spectral Energy Distributions (SEDs), color-color diagrams, and images of three representative star clusters from Henny et al. 2025 – Fig. 1.

PAH emitters

Rodriguez et al. 2025 - A set of F335M vs F300M - F335M color magnitude diagrams for 19 galaxies. This shows how the 3.3 PAH-emitters are selected as the objects in the upper right part of each panel.

Selection of 3.3 PAH emitters based on color-magnitude diagrams from Rodriguez et al. 2025 – Fig 11.

Distribution of peak CO intensity

e et al. 2026 (in preparation) - Eight panels showing histograms of the CO intensity at the locations of star clusters for 8 different age ranges. There is a steady increase of the CO intensity for the younger clusters with the highest value being for the youngest set of clusters in the upper left panel (i.e., 1 - 3 Myr (YNO = Young Nebular Object)),  consistent with the removal of the GMCs (Giant Molecular Clouds) by feedback at very young ages.

Distribution of peak CO intensity at the location of  star clusters within different age bins from He et al. 2026 (in preparation).

Mass function of star clusters

Chandar et al. 2026 (in preparation) - Eight panels showing the mass functions of star clusters grouped in order of decreasing integrated star formation, with the highest star formation rates in the upper left panel and the lowest in the lower right. Symbol color indicates age range from blue (youngest) to red (oldest). The mass functions are all quite similar showing a nearly universal behavior.

The mass function of star clusters for eight galaxy groupings (in order of decreasing integrated star formation) is nearly universal, from Chandar et al. 2026 (in preparation). Symbol color indicates age range (blue being younger).

Overview

The PHANGS program is building a panchromatic dataset to enable the multi-phase, multi-scale study of star formation across nearby spiral galaxies.  PHANGS combines Atacama Large Millimeter/submillimeter Array (ALMA) CO(2-1) mapping, Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT/MUSE) optical spectroscopy, Hubble Space Telescope (HST) UV-optical imaging, and James Webb Space Telescope (JWST) infrared imaging among other supporting datasets.   PHANGS is using these data to study the star formation cycle and various phases of the interstellar medium.

Here, the team provides catalog products from the PHANGS survey. The PHANGS-HST Treasury has yielded a V-band selected census of ~100,000 star clusters and compact associations across the disks of 38 spiral galaxies (plus 1 companion dwarf galaxy) at distances of 4-23 Mpc.

Data Release Notes

  • Catalogs combining the previously released DR4 HST photometry, with improved estimates of age, mass, and reddening, provided for star clusters and compact associations across the full sample of 38 PHANGS-HST spiral galaxies (+1 companion galaxy). These catalogs include results for a total of ∼100,000 sources. The HST photometry is unchanged from DR4, while the physical properties are based on an enhanced SED-Treefit analysis that builds on the results first provided in DR3, using the methods described in Thilker et al. 2025, as introduced by Whitmore et al. 2023.

    Catalogs for multi-scale associations (from Larson et al. 2023 - preferred over the compact association catalogs), and using additional JWST data, will be provided at a future date.

Data Products Description

Data Products Descriptions

  • These catalogs combine the previously released DR4 HST photometric measurements with enhanced physical properties (ages, masses, and reddening) for roughly 100,000 star clusters and compact associations across 39 galaxies (40 target fields).

    Primary changes relative to DR3 and DR4 include:

    1. Concatenation of individual galaxy catalogs into survey-wide catalogs that include all galaxies. (Note: Individual files for each galaxy are NOT provided in the Data Access Table.)
    2. Updated physical properties based on improved HST SED fitting using the methods described in Thilker et al. (2025).
    3. Addition of exploratory physical properties based on SED fitting that incorporates both HST and JWST/NIRCam data, as described in Henny et al. (2025).

    The catalog files have the following naming convention:

    For the 4 PRIMARY files:

    hlsp_phangs-cat_hst_acs-uvis_dr5-targets_<version>_<type-1>-<type-2>-primary.fits
    

    where:

    •  <version> = "v1" for version 1 of the DR5 catalogs,
    •  <type-1> = Type of file: "human" classified or "machine" learning classified, 
    • <type-2> = Type of file:
              "class1+2" - symmetric and asymmetric clusters or "class3" - compact associations.

    Examples: hlsp_phangs-cat_hst_acs-uvis_dr5-targets_v1_human-class1+2-primary.fits

    For the 1 SUPPLEMENTAL file:

    hlsp_phangs-cat_hst_acs-uvis_dr5-targets_<version>_supplemental.fits
    

    where:

    •  <version> =  "v1" for version 1 of the DR5 catalogs

    Example: hlsp_phangs-cat_hst_acs-uvis_dr5-targets_v1_supplemental.fits

Data Access

DR4 - Catalog Release 2

Please see the data table on the PHANGS page for downloads for galaxy-specific cluster and compact association photometric catalogs.

DR3 - Catalog Release 1

Download tar files containing every CLUSTER or ASSOC product across all available galaxies in the table below.  A copy of the README files are included in each tar file, but are also linked on their own for direct access in the table below.  The README files explain the catalog columns in more detail, and also include information about the galactic extinction tables, aperture corrections, and assumed distances.

CLUSTER Bundle

ASSOC Bundle

Catalogs: hlsp_phangs-cat_hst_wfc3_all_multi_v1_cc-cats.tar.gz

Catalogs: hlsp_phangs-cat_hst_wfc3_all_multi_v1_assoc-cats.tar.gz

README: hlsp_phangs-cat_hst_wfc3_all_multi_v1_compact-cluster-readme.txt

README: hlsp_phangs-cat_hst_wfc3_all_multi_v1_assoc-readme.txt

 

Download tar files containing every CLUSTER or ASSOC product for a specific galaxy using the table below.

Galaxy

Distance (Mpc)

CLUSTER Bundle ASSOC Bundle

NGC 1433

8.3 hlsp_phangs-cat_hst_wfc3_ngc1433_multi_v1_cc-cats.tar.gz hlsp_phangs-cat_hst_wfc3_ngc1433_multi_v1_assoc-cats.tar.gz

NGC 1559

19.4 hlsp_phangs-cat_hst_wfc3_ngc1559_multi_v1_cc-cats.tar.gz hlsp_phangs-cat_hst_wfc3_ngc1559_multi_v1_assoc-cats.tar.gz

NGC 1566

18.0 hlsp_phangs-cat_hst_wfc3_ngc1566_multi_v1_cc-cats.tar.gz hlsp_phangs-cat_hst_wfc3_ngc1566_multi_v1_assoc-cats.tar.gz

NGC 3351

10.0 hlsp_phangs-cat_hst_wfc3_ngc3351_multi_v1_cc-cats.tar.gz hlsp_phangs-cat_hst_wfc3_ngc3351_multi_v1_assoc-cats.tar.gz

NGC 3627

10.1 hlsp_phangs-cat_hst_wfc3_ngc3627_multi_v1_cc-cats.tar.gz hlsp_phangs-cat_hst_wfc3_ngc3627_multi_v1_assoc-cats.tar.gz

 

Information about the DR3 star cluster catalogs below may be of interest (this information is updated in DR4 and provided in Maschmann, Lee, Thilker, Whitmore, et al. submitted).

Galaxy

Distance

(Mpc)

m-M

mv

human_cutoff

Mv

human_cutoff

human

class1

human

class2

mv

machine_cutoff

Mv

machine_cutoff

machine

class1

machine

class2

ngc1433

8.3 29.6 24.1 -5.5 90 101 25.2 -4.4 209 132

ngc1559

19.4 31.4 23.5 -7.9 419 301 25.7 -5.8 659 494

ngc1566

18.0 31.3 23.5 -7.8 379 271 25.2 -6.1 796 398

ngc3351

10.0 30.0 24.0 -6.0 137 166 25.4 -4.6 439 246

ngc3627

10.1 30.0 22.5 -7.5 462 312 24.9 -5.2 1725 820

Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work. 

Note: These HLSP data products are licensed for use under CC BY 4.0.

References