Mission Overview

PHAT AGB Stars and Other Cool Giants in M31 Star Clusters (PHATAGB)


Primary Investigator: Léo Girardi

HLSP Authors: Léo Girardi

Released: 2020-10-09

Updated: 2020-10-09

Primary Reference(s): Girardi et al. 2020

DOI: 10.17909/t9-mn5h-8e38

Citations: See ADS Statistics

Read Me: Clusters

PHATAGB Finder Chart
Finding chart for the AGB candidates contained in the cluster AP274. The left panel shows a false-color representation of the PHAT F475W+F814W optical images, which was used to find the clusters and derive their morphological parameters in Johnson et al. (2015), while the right panel shows the F160W image, whose photometry is crucial for identifying the AGB stars in this work. Images are centered on the cluster and have dimensions of 15 arcsec x 15 arcsec (or 5.7 pc x 5.7 pc), with North up and East left. In green we mark the cluster centre and aperture radius Rap, in red (in the F160W image only) all the candidate AGB stars in the area.



The team provides a list of 937 candidate asymptotic giant branch (AGB) stars in M31 star clusters from the Panchromatic Hubble Andromeda Treasury survey, together with their finding charts. The photometric criteria selects stars brighter than the tip of the red giant branch, which includes the bulk of the thermally pulsing AGB stars as well as early-AGB stars and other luminous cool giants expected in young stellar populations (e.g., massive red supergiants, and intermediate-mass red helium-burning stars). The AGB stars can be differentiated using the ages estimated for the clusters. Cross-matching with additional databases reveals two carbon stars and 10 secure variables among them.

Data Products

The data file naming convention for the catalog file is as follows:


NOTE: Many clusters have multiple candidate AGB stars, therefore a given AP ID may be in the cluster catalog file more than once.

The file naming convention for the finder charts is as follows:



  • <#> is the cluster number, not zero-padded.

Data file types:

_clusters.fits Catalog of RGB stars in clusters.
_findingchart.png Three-color image centered on each cluster.

Data Access

You can download the catalog of RGB stars here: hlsp_phatagb_hst_wfc3-uvis-acs-wfc-wfc3-ir_all_multi_v1_clusters.fits.  A description of the catalog and the available columns can be found in the README file linked at the top of the page.

You can see a page of finder charts centered on each cluster here.


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.