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.

• 44,729 files from 272 programs, 7.26 TB, public by 2026-10-28.
• index.parquet lists every file with its exposure metadata, and backgrounds.parquet lists the 5,435 dedicated sky-background exposures of the same programs (1.14 TB), which are not included.

Contents

Role	Exposures	Files	Programs	TB
mid-infrared imaging	MIRI imaging in every filter	13,332	98	3.07
mid-infrared spectroscopy	MIRI medium-resolution integral-field spectroscopy (MRS)	9,004	104	1.82
starlight baseline	NIRCam long-wavelength imaging (2.4-5 µm) of sky MIRI also imaged, and of the Magellanic Clouds, M31 and M33	14,279	131	0.99
local group stars	NIRCam short-wavelength imaging in the wide filters of the Magellanic Clouds, M31 and M33	4,994	25	0.32
high-resolution spectroscopy	NIRSpec multi-object spectroscopy with the G140H, G235H and G395H gratings	1,056	24	0.58
nearby galaxy spectroscopy	NIRSpec integral-field and fixed-slit spectroscopy with the high-resolution gratings, of the 97 nearest galaxy targets	2,064	32	0.49

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 whose target position lies in the box around the Large Magellanic Cloud (RA 60-100, Dec -76 to -63), the Small Magellanic Cloud (RA 0-30, Dec -76 to -70), M31 (RA 7-14.5, Dec 38.5-44) or M33 (RA 22.6-24.3, Dec 29.9-31.4). Programs 3707, 4204, 4434, 4445 and 5594, on objects behind the Clouds, carry no box's label, and local_group names the box.

Left out are calibration, commissioning and engineering programs, apart from the Early Release Observations filed under commissioning; programs on objects in the Milky Way, among them the Galactic Center, 47 Tucanae and brown dwarfs (1238, 1266, 1293, 2075, 2124, 2235, 2302, 2473, 2491, 2559, 2560, 3153, 3786, 5650, 5835, 5896, 8441, 10678, 12628); Solar System and other moving targets; 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 and medium-resolution spectra, and integral-field and fixed-slit spectra beyond the nearest galaxies; 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 and fixed-slit spectra are not thinned, since successive passes target different objects.

Integral-field and fixed-slit targets in the galaxy, galaxy cluster and unidentified categories outside the four Local Group boxes are matched to the nearest non-stellar SIMBAD object with a redshift within 5 arcseconds and ranked by the size of that redshift. Each matched object keeps the visit with the longest exposure in each grating, and the ranking stops at z = 0.0858; redshift and simbad_id in the index carry the match.

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, and for the nearby galaxy spectra redshift and simbad_id. 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.