2MASS Point Source Catalog sample
raw/2mass_psc_m31_0p5deg.tbl is an unmodified IPAC ASCII-table response from the
NASA/IPAC Infrared Science Archive (IRSA) Gator service, drawn from the 2MASS
All-Sky Point Source Catalog (PSC).
It is a circular field of view centred on M31:
- Centre: ICRS/J2000 RA 10.6847083 deg, Dec +41.2687500 deg
- Cone radius: 0.5 deg
- Retrieved rows: 9,047
- Retrieval date: 2026-08-25 (recorded in the table header)
The all-sky PSC has hundreds of millions of entries, so it is deliberately not
vendored. This real-survey slice keeps the repository lightweight while
providing a reproducible replacement for the synthetic latitude/longitude grid.
Run bash scripts/download_2mass_psc_m31.sh from any directory to refresh it.
The table preserves the service response. Its relevant source fields are:
| Field | Meaning |
|---|---|
ra, dec |
ICRS/J2000 right ascension and declination, in degrees |
j_m, h_m, k_m |
2MASS J, H, and Ks default magnitudes, in mag |
dist |
Angular distance from the stated field centre, in arcsec |
rd_flg |
Per-band source/read flag needed to interpret the default magnitudes |
j_m, h_m, and k_m may be null in the original PSC. No temperature is
included or inferred: the PSC provides photometry, not source temperatures.
Do not treat magnitudes as linear fluxes without applying the appropriate 2MASS
band zero points.
processed/2mass_psc_m31_0p5deg_stars.csv is generated from the raw table by
python3 scripts/process_2mass_psc.py. It retains only ra_deg, dec_deg,
temperature_K, and amplitude_sr. See its directory README for the fitting
model and quality cut.
raw/2mass_psc_m44_1p0deg.tbl is the corresponding unmodified 1.0-degree
cone around M44 (Beehive/Praesepe), centred on ICRS/J2000 RA 129.99165 deg and
Dec +19.54139 deg. It contains 8,790 retrieved PSC rows (2026-08-25) and is
downloaded by
bash scripts/download_2mass_psc_m44.sh; process it with:
python3 scripts/process_2mass_psc.py \
--input assets/2mass/raw/2mass_psc_m44_1p0deg.tbl \
--output assets/2mass/processed/2mass_psc_m44_1p0deg_stars.csv
The resulting M44 CSV contains 7,802 sources after the documented three-band
photometry and rd_flg selection.
Full-sky acquisition
scripts/download_2mass_psc_all_sky.py provides a resumable full-sky
acquisition without asking IRSA for a cone larger than 1 degree. Inspect its
storage plan before starting the long download:
python3 scripts/download_2mass_psc_all_sky.py --plan
python3 scripts/download_2mass_psc_all_sky.py --download --workers 2
It covers each latitude band with integer-RA cone sectors, wider at high
latitudes, while outputs are cleaned and retained by unique 1-degree RA/Dec
ownership cells. Cone overlap cannot create duplicate stars. Temporary raw
tables and cleaning intermediates are stored under /tmp/2mass_psc_all_sky/
and deleted after each successful cover. The generated full-sky catalogue has
one CSV per ownership cell under processed/all_sky/, named
tile_raRRR_decDDD.csv. RRR is
floor(RA_deg mod 360) and DDD is min(179, floor(Dec_deg + 90)); the
corresponding range is [RRR, RRR+1) x [DDD-90, DDD-89) degrees. It is
intentionally not a single CSV because that would duplicate a roughly 15--17
GiB result during merging.
See that directory's README for restart and raw-retention behavior.
Provenance: IRSA Gator program interface, 2MASS PSC column descriptions.