astro-legacy-archive/cobe-firas-cmb-monopole

COBE/FIRAS CMB monopole spectrum

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This dataset contains the 43-point COBE/FIRAS cosmic microwave background monopole spectrum published by LAMBDA. It includes the monopole intensity, its residual from a 2.725 K blackbody, the published one-sigma uncertainty, and a model of Galactic emission at the Galactic poles. The columns retain the source file's own labels, Column 1 through Column 5; their meanings and units are documented below.

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-monopole", "v1", split="train[:1]", columns=["Column 1", "Column 2"])
row = dataset[0]
print(row["Column 1"], row["Column 2"])

2.27 200.723

import json
from huggingface_hub import hf_hub_download
import pyarrow.parquet as pq
path = hf_hub_download("astro-legacy-archive/cobe-firas-cmb-monopole", "v1.parquet", repo_type="dataset")
print(json.loads(pq.read_metadata(path).metadata[b"statistical_product"])["schema"])

astro-legacy-archive/statistical-product

The embedded statistical-product document records the source labels, units, descriptions, covariance relation, and complete source header. Column 1 is wavenumber in cm^-1 and Column 2 is monopole intensity in MJy/sr.

Dataset structure

There is one row per published spectral sample, in source order, with no nulls. Column 1 is strictly increasing.

Column 1 is a wavenumber, despite the source description's word "frequency". Column 2 ranges from 4.523 to 383.478 MJy/sr. Column 3 ranges from -432 to 58 kJy/sr. All 43 values in Column 4 are positive, spanning 10 to 282 kJy/sr, while Column 5 spans -1 to 573 kJy/sr.

The uncertainty in Column 4 applies to both the blackbody-plus-residual Column 2 and residual Column 3: adding the fixed 2.725 K blackbody does not change the absolute kJy/sr uncertainty. Fixsen et al. (1996), section 3.3, defines the frequency-frequency covariance approximation C_nu,nu' = sigma_nu sigma_nu' Q(|nu-nu'|). This LAMBDA product supplies the per-sample sigma values but neither Q nor a covariance matrix.

PyArrow schema inspection exposes each field's complete source definition and unit. load_dataset retains the column types but does not expose field metadata through Dataset.features. The embedded statistical_product metadata records the roles and source relationship: Column 1 is the independent variable; Column 2 and Column 3 are values; Column 4 is the one-sigma uncertainty of Column 3; Column 5 is a model.

Provenance

• —Product page: COBE/FIRAS CMB Monopole Spectrum
• —Download page: FIRAS monopole spectrum data
• —Source file: `firas_monopole_spec_v1.txt`, 2,388 bytes, SHA-256 df793c3dca09ebfa7dbc5aa0ec1951daa8884431bc30eff28a710d7516cf50fa
• —Source dataset identifier: ADS/Sa.COBE#firas_monopole_spec_v1.txt

The source is a 61-line whitespace-delimited ASCII file: 18 leading comment lines and 43 measurement rows. The LAMBDA download page gives a delivery date of 2003-03-01, while the embedded revision history states v1 : initial release, May 2005. The checked source pages publish no reconciliation of those statements.

The complete source header is embedded with the five numeric columns.

Considerations for use

• —Column 1 is wavenumber in cm^-1, not frequency in Hz.
• —Column 2 is in MJy/sr; Column 3, Column 4, and Column 5 are in kJy/sr.
• —Correlated-error analyses need the frequency-correlation information described by Fixsen et al. (1996), which is not included in this product.
• —Column 5 is a modeled Galaxy spectrum at the Galactic poles, not another CMB monopole measurement.

Licensing and credit

HEASARC states verbatim:

HEASARC materials are all available freely for your use.

This is a free-use statement rather than a named formal licence.

No explicit licence is published.

No requested credit line is published.

Citations

The residuals and uncertainties come from Fixsen et al. (1996). The subsequent calibrator analysis and final FIRAS spectral-results summary provide further context.

@article{Fixsen1996FIRAS,
  author = {Fixsen, D. J. and Cheng, E. S. and Gales, J. M. and Mather, J. C. and Shafer, R. A. and Wright, E. L.},
  title = {The Cosmic Microwave Background Spectrum from the Full COBE/FIRAS Data Set},
  journal = {The Astrophysical Journal},
  volume = {473},
  pages = {576--587},
  year = {1996},
  doi = {10.1086/178173},
  eprint = {astro-ph/9605054},
  archivePrefix = {arXiv}
}

@article{Mather1999FIRAS,
  author = {Mather, J. C. and Fixsen, D. J. and Shafer, R. A. and Mosier, C. and Wilkinson, D. T.},
  title = {Calibrator Design for the COBE Far-Infrared Absolute Spectrophotometer (FIRAS)},
  journal = {The Astrophysical Journal},
  volume = {512},
  pages = {511--520},
  year = {1999},
  doi = {10.1086/306805},
  eprint = {astro-ph/9810373},
  archivePrefix = {arXiv}
}

@article{Fixsen2002FIRAS,
  author = {Fixsen, D. J. and Mather, J. C.},
  title = {The Spectral Results of the Far-Infrared Absolute Spectrophotometer Instrument on COBE},
  journal = {The Astrophysical Journal},
  volume = {581},
  pages = {817--822},
  year = {2002},
  doi = {10.1086/344402}
}

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. Dataset requests and archive-wide questions may be posted in the Community tab of any dataset. Confirmed corrections are made in the source conversion tools and published by rebuilding the dataset.