astro-legacy-archive/qmap-raw-maps

QMAP raw sky maps

[image]

The preview projects the source x, y, and z unit vectors onto a north polar view and colours each source row by T; the dataset itself retains only the five source columns.

Regenerate it from the published Parquet data with python tools/render_hub_preview.py qmap-raw-maps datasets/qmap-raw-maps/preview.png.

This dataset contains the six raw QMAP sky-map tables served by LAMBDA. QMAP observed a region around the North Celestial Pole during two balloon flights in 1996. Each configuration is one source filename stem and retains every source row and column in its original order.

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/qmap-raw-maps", "1Ka12_cmbmap", split="train[:1]", columns=["x", "y", "z", "T", "sigma"])
row = dataset[0]
print(row["T"], row["sigma"])

-3160.66872 1967.56201

import json
from huggingface_hub import hf_hub_download
import pyarrow.parquet as pq
path = hf_hub_download("astro-legacy-archive/qmap-raw-maps", "1Ka12_cmbmap.parquet", repo_type="dataset")
print(json.loads(pq.read_metadata(path).metadata[b"statistical_product"])["schema"])

astro-legacy-archive/statistical-product

Dataset structure

Each row is one source sky pixel. LAMBDA names the five columns x, y, z, T, and sigma. The first three are the pixel unit vector in equatorial coordinates. T is the measured temperature fluctuation and sigma is its rms noise; both are in micro-Kelvin.

All fields are stored as float64. No pixel identifier, coordinate conversion, filter flag, or other derived column is added. The source files have no header; the embedded metadata attaches LAMBDA's published definition, unit, role, and source position to each field.

Provenance

LAMBDA publishes the QMAP product description and download table. The six pinned source files are:

Considerations for use

• —The six configurations represent separate detector combinations and flights; compare them using their source identities.
• —LAMBDA states that noise is correlated between pixels. sigma is the rms noise per row, not a complete covariance representation.
• —LAMBDA separately serves Wiener-filtered maps for visual inspection. Those derived products are not included here.

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.

Citation

The mapmaking and combined results are described by de Oliveira-Costa et al. (1998), The Astrophysical Journal, 509, L77, doi:10.1086/311759.

Errata and requests

Report corrections or dataset requests in the dataset's Community tab.