Mission Overview

The GLASS JWST Early Release Science Program



Primary Investigator: Tommaso Treu


Released: 2023-07-07

Updated: 2023-07-07

Primary Reference(s): Treu, T. et al. 2022, Paris, D., et al. 2023

DOI: 10.17909/kw3c-n857

Citations: See ADS metrics

Read Me (see also: author README)

Source Data:

Abell 2744 Cluster
Color composite (RGB) image of the Hubble Frontier Field cluster Abell 2744, derived by combining the F090W+F115W+F150W as blue, F200W+F277W as green and F356W+F410M+F444W as red. Colored borders show the position of the three different JWST data sets used here: GLASS (green), UNCOVER (GO-2561, blue) and DD-2756 (red). The entire image (including the empty space) is approximately 12.7 × 5.9 arcmin on the sky.



The GLASS-JWST Early Release Science Program (hereafter GLASS-JWST ERS) has obtained the deepest observations of galaxies obtained of all Early Release Science Programs by targeting the Hubble Frontier Field, and in particular the lensing cluster Abell 2744. This high-level science product collection combines the GLASS-JWST NIRCam imaging data (ERS-1324) with NIRCam data from two other JWST programs targeting the same field: UNCOVER (GO-2561; PI: I. Labbé and R. Bezanson) and Program DD-2756 (PI: W. Chen). The observed area in the wide-band filters - covering the central and extended regions of the cluster, as well as new parallel fields - is 46.5 arcmin2 in total.

Data Products

This collection includes JWST NIRCam mosaics plus root-mean-square (RMS) maps for 8 IR filters (see below). The mosaics were produced by the JWST calibration pipeline, as supplemented by several custom procedures developed by the GLASS-JWST team to correct for residual defects that were not addressed in standard processing. All mosaics are in FITS format with brightness in μJy/sr and a zero-point of ZP_AB = 23.9.

This collection also includes a mult-wavelength catalog consisting of photometry from these mosaics, and is combined with publicly available HST photometry in the F435W, F606W, F775W and F814W ACS bands, and in the F105W, F125W, F140W and F160W WFC3 bands. The photometric catalog was derived by detecting objects in the NIRCam F444W image and computing PSF-matched forced photometry on the remaining bands, using various apertures. The apertures sizes were 0.28′′, 0.56′′, 1.12′′ and 2.24′′ (corresponding to 2×, 3×, 8× and 16× the point-spread function (PSF) of the F444W image, respectively), and also the isophotal (segmentation) aperture. The resulting catalog contains 24,389 sources.

Data file naming convention:



  • <filt> is the filter name, one of "f090w", "f115w", "f150w", "f200w", "f277w", "f356w", "f410m", "f444w"
  • <prodType> is the product semantic type, shown below:

Science image

_rms RMS image
_cat Source catalog

Data Access

GLASS-JWST images are available in the MAST Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write), and via the direct download table below. Set the Provenance Name filter to GLASS-JWST in the Portal Advanced Search to find all or individual images.

from astroquery.mast import Observations
all_obs = Observations.query_criteria(provenance_name="glass-jwst")
data_products = Observations.get_product_list(all_obs)
  • A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory
  • Search for and retrieve GLASS-JWST data products programmatically.

Direct Download

Access the JWST NIRCam mosaics from the table below, by filter. The file sizes are all approximately 1.9 GB.

Content Type NIRCam Filter









RMS F090W F115W F150W F200W F277W F356W F410M



The catalog file consists of a FITS file with multiple BINTABLE extensions, named corresponding to the photometric aperture on which the photometry was performed.


Be sure 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.