astro-legacy-archive/cobe-firas-cmb-temperature-map

COBE/FIRAS CMB Temperature Map

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This dataset contains LAMBDA's 6,067-row CMB Temperature Map FITS table. The source fields remain PIXEL, GAL_LON, GAL_LAT, WEIGHT, TEMP, TEMP_SIG, and RESID_TE, in order and with their source values and units unchanged.

How to use

python -m venv .venv && .venv/bin/pip install datasets huggingface_hub pyarrow

from datasets import load_dataset
dataset = load_dataset("astro-legacy-archive/cobe-firas-cmb-temperature-map", "FIRAS_TEMPERATURE_MAP_LOWF", split="train[:1]", columns=["PIXEL", "TEMP", "TEMP_SIG"])
row = dataset[0]
print(row["PIXEL"], row["TEMP"], row["TEMP_SIG"])

0 2.725238084793091 0.00027390586910769343

from huggingface_hub import hf_hub_download
import json
import pyarrow.parquet as pq
path = hf_hub_download(repo_id="astro-legacy-archive/cobe-firas-cmb-temperature-map", repo_type="dataset", filename="FIRAS_TEMPERATURE_MAP_LOWF.parquet")
print(json.loads(pq.read_metadata(path).metadata[b"explicit_pixel_table"])["physics"]["file_average_cmb_temperature_k"]["value"])

2.727754

Fields and map geometry

Appendix G defines PIXEL as the FIRAS resolution-6 pixel number, GAL_LON and GAL_LAT as Galactic coordinates in degrees, and WEIGHT as pixel weight. TEMP is CMBR temperature in the pixel in K; TEMP_SIG is its sigma in K; RESID_TE is the CMBR temperature residual in the pixel in K. The abbreviated TTYPE spellings remain unchanged even where the source comment expands them as TEMP_SIGMA and RESID_TEMP.

The table has 6,067 unique source pixel rows. LAMBDA documents FIRAS maps as an ecliptic quadrilateralized spherical cube with six 32×32 faces at resolution index 6. That describes a 6,144-pixel domain, not permission to insert the 77 absent identifiers. The stored Galactic coordinates and weights remain the authority for each released row.

Scientific context

The product page summarizes the average as 2.728 ± 0.004 K. The file records a distinct fitted value and uncertainty: CBR_TEMP=2.727754 K and CBR_SIG=0.002 mK. It also records DIP_AMP=3.3506 mK, DIP_SIG=0.006 mK, DIP_LON=264.98 deg, DIP_LAT=47.92 deg, DIR_SIG=0.09 deg, and RMS_TEMP=0.214 mK. These file-level parameters are structured under physics; they are not row columns.

TEMP is a derived analyzed science product, not a direct thermodynamic detector timestream. RESID_TE is the released residual and is not recomputed by subtracting an archive model. Users assessing dipoles, large-scale modes, or uncertainties should consult the source header and FIRAS analysis papers; this mirror does not add a covariance model or treat TEMP_SIG values as independent by assumption.

Provenance and reconstruction

The Parquet retains every source row and field in order, including float32 value bits and blank/source units. Its explicit_pixel_table metadata records the source URL, byte count, SHA-256, both FITS headers, column descriptions, QUADTREE resolver evidence, physical fit parameters, rights, credit, and the regeneration record.

To construct a dense display, prefill a 6,144-element array with an explicit missing value and assign TEMP at the released PIXEL identifiers. Do not equate table row ordinal with pixel number, derive replacement coordinates, or fill missing sky-cube cells. Preserve TEMP_SIG and RESID_TE as separate released quantities.

Source: https://lambda.gsfc.nasa.gov/product/cobe/firascmbtmget.html. The source FITS file is 181,440 bytes with SHA-256 a49ec2af81d0890be9ad6781488bc9a27bd78b37c3be28c86c7eddb474ac2f6c. Rebuild with python tools/make_firas_explicit_pixel_products.py --out data --source /var/tmp/will/firas-explicit/source --provenance-commit <commit>.

HEASARC's data policy states, verbatim: “HEASARC materials are all available freely for your use.” Its requested acknowledgement is: “This research has made use of data and/or software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC.” LAMBDA's COBE credit is, verbatim: “The COBE datasets were developed by the NASA Goddard Space Flight Center under the guidance of the COBE Science Working Group.”

Description: https://lambda.gsfc.nasa.gov/product/cobe/firascmbtemp.html. Record definitions: https://lambda.gsfc.nasa.gov/data/cobe/firas/doc/FES4APPG.TXT. Sky-cube description: https://lambda.gsfc.nasa.gov/product/cobe/firasproducts.html.

Errata and requests

To report an erratum, propose a correction, or ask a question about this dataset, open a Discussion or Pull Request in its Community tab; posting requires a free Hugging Face account. Confirmed corrections are made in the source conversion tools and published by rebuilding the dataset.