astro-legacy-archive/qmap-raw-maps

QMAP raw sky maps

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_schema(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.

configuration	rows
1Ka12_cmbmap	2,695
1Q2_cmbmap	2,754
1Q34_cmbmap	2,937
2Ka12_cmbmap	1,625
2Q12_cmbmap	1,633
2Q34_cmbmap	1,591

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:

source file	bytes	SHA-256
1Ka12_cmbmap.dat	188,650	4e79ed2ded596e41dbb916cf9b5639b3dd53da27495ac4f3f31e571bf296e1ad
1Q2_cmbmap.dat	192,780	4e294badde58cf1122027a3a8926169a67cd725302f9c8f847a435f791bb89c3
1Q34_cmbmap.dat	205,590	9bd1fa37a92be368765e5356db31d50a28e54df852e9c41cd2cb509c12d185ad
2Ka12_cmbmap.dat	113,750	b7cb6e3ed745048d1f5db928d92cd87c18479215b19fac037e656db23c4ff9fc
2Q12_cmbmap.dat	114,310	3209ce20f08f917b8f1a45551554acf764bd56d089ef6bdfd03570fc68d17e50
2Q34_cmbmap.dat	111,370	ff34ad89394107458a7866314d45417a43d910870ca7bc2188dd6ef8c567fa9e

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.