phanerozoic/jwst-extragalactic-uncal

JWST extragalactic raw exposures

Raw exposures from the James Webb Space Telescope as MAST distributes them, the level-1b _uncal.fits files that hold the detector counts of every group of every integration before any calibration, chosen for three extragalactic technosignature searches: mid-infrared waste heat from galaxies against their starlight, single anomalous stars in the galaxies of the Local Group, and narrow lines in the spectra of galaxies.

• 47,355 files from 339 programs, 7.39 TB, public by 2026-10-28.
• index.parquet lists every file with its exposure metadata, and backgrounds.parquet lists the 5,838 dedicated sky-background exposures of the same programs (1.22 TB), which are not included.

Contents

Role	Exposures	Files	Programs	TB
mid-infrared imaging	MIRI imaging in every filter	14,643	133	3.19
mid-infrared spectroscopy	MIRI medium-resolution integral-field spectroscopy (MRS)	9,995	121	2.00
starlight baseline	NIRCam long-wavelength imaging (2.4-5 µm) of sky MIRI also imaged, and of the Magellanic Clouds, M31 and M33	15,716	172	1.12
local group stars	NIRCam short-wavelength imaging in the wide filters of the Magellanic Clouds, M31 and M33	5,780	38	0.44
high-resolution spectroscopy	NIRSpec multi-object spectroscopy with the G140H, G235H and G395H gratings	1,221	27	0.65

Selection

The candidates are the public science exposures whose target category in the observing proposal is a galaxy, a cluster of galaxies or an unidentified source (blank fields), or whose program's science category is extragalactic (galaxies, high-redshift galaxies, large-scale structure, active galaxies and supermassive black holes, the intergalactic and circumgalactic medium, cosmology), together with every exposure pointed within the Large and Small Magellanic Clouds, M31 and M33.

Left out are time-series observations; target acquisitions and engineering exposures; exposures STScI flags for a telemetry problem, suspect engineering quality or a superseded version; dedicated sky backgrounds; NIRSpec prism, medium-resolution, integral-field and fixed-slit spectra; slitless spectroscopy; MIRI low-resolution spectroscopy; NIRISS; NIRCam short-wavelength imaging outside the four Local Group galaxies; and NIRCam long-wavelength imaging of sky MIRI did not image.

Repeat coverage is thinned within each mode and filter, with the grating for NIRSpec and the band and detector for MRS. Visits are taken deepest first, depth being effective exposure time per footprint cell, and a visit is kept whole, every dither and detector, when at least half of its footprint on a 20-arcsecond grid (1 arcsecond for integral-field data) is not yet covered. Multi-object spectra are not thinned, since successive passes target different objects.

Data

Each file is the archive's _uncal.fits, unchanged, copied from MAST's public bucket on AWS (s3://stpubdata/jwst/public/) to data/<program>/<visit>/<file>, the bucket's own layout, and each copy's size is checked against the bucket listing.

The files are calibrated with STScI's pipeline (pip install jwst), which fetches its reference files from CRDS: calwebb_detector1 turns an _uncal file into count rates, calwebb_image2 or calwebb_spec2 into a calibrated exposure, and calwebb_image3, calwebb_spec3 or the MRS and IFU cube builders combine the exposures of an association. The background exposures in backgrounds.parquet can be fetched from MAST by mast_uri or from the bucket by s3_key where a reduction needs them.

Index

index.parquet has one row per file: path, filename, program, observation, visit, exposure, detector, instrument, exp_type, role, filter, pupil (NIRCam), band (MRS), grating (NIRSpec), channel (NIRCam SW or LW), readpatt, ngroups, nints, subarray, effexptm (s), date_obs (UTC), public_release, target_name, target_proposer_name, target_category, target_description, science_category, program_title, pi_name, targ_ra, targ_dec (deg), s_region (the exposure's footprint), local_group (LMC, SMC, M31, M33 or empty), size (bytes), s3_key, mast_uri. backgrounds.parquet has the same columns apart from path.

Acknowledgement

JWST mission data in MAST are in the public domain under the MAST data use policy. Publications based on them carry the JWST acknowledgement:

This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-03127 for JWST.

and cite the programs used, which program and pi_name identify.