Each filename starts with a Grizli root identifier followed by the source ID as so:

"jXXXXYYmZZZZ_AAAA" or "jXXXXYYpZZZZ_AAAA"

where X gives the SpARCS ID and A gives the source ID.

For each GCLASS cluster, a .zip file is available below. Within each of these files, there are 4 types of files:

• "_thumb.fits" files contain four fits extensions:

1. "SCI" is the direct image thumbnail in HST WFC3 F140W.

2. "PSF" is the HST WFC3 F140W point spread function thumbnail.

3. "WHT" is the weight map for the direct image thumbnail. These are inverse variance maps.

4. "SEG" is the segmentation map for the direct image thumbnail.

• "_thumb.png" files offer a quick look at the direct image thumbnail, with an rgb image also included*

• "_rgb.png" files offer a quick look at the rgb image*

• "_seg.png" files are pngs of the segmentation map for each thumbnail, with each segment labelled with the source ID.

* rgb images are only useful when there is imaging in three different HST filters. For this dataset, only F140W is available, so F140W is used in all three channels.

Further details on all these files and how these files were created with Grizli can be found in the Grizli documentation here.