The Effelsberg-Bonn H i Survey: Milky Way gas^⋆

First data release

¹ Argelander-Institut für Astronomie (AIfA), Auf dem Hügel 71, 53121 Bonn, Germany
² Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: bwinkel@mpifr.de

Received: 20 July 2015
Accepted: 26 October 2015

Abstract

Context. The Effelsberg-Bonn H i Survey (EBHIS) is a new 21-cm survey performed with the 100-m telescope at Effelsberg. It covers the whole northern sky out to a redshift of z ~ 0.07 and comprises H i line emission from the Milky Way and the Local Volume.

Aims. We aim to substitute the northern-hemisphere part of the Leiden/Argentine/Bonn Milky Way H i survey (LAB) with this first EBHIS data release, which presents the H i gas in the Milky Way regime.

Methods. The use of a seven-beam L-band array made it feasible to perform this all-sky survey with a 100-m class telescope in a reasonable amount of observing time. State-of-the-art fast-Fourier-transform spectrometers provide the necessary data read-out speed, dynamic range, and spectral resolution to apply software radio-frequency interference mitigation. EBHIS is corrected for stray radiation and employs frequency-dependent flux-density calibration and sophisticated baseline-removal techniques to ensure the highest possible data quality.

Results. Detailed analyses of the resulting data products show that EBHIS is not only outperforming LAB in terms of sensitivity and angular resolution, but also matches the intensity-scale of LAB extremely well, allowing EBHIS to be used as a drop-in replacement for LAB. Data products are made available to the public in a variety of forms. Most important, we provide a properly gridded Milky Way H i column density map in HEALPix representation. To maximize the usefulness of EBHIS data, we estimate uncertainties in the H i column density and brightness temperature distributions, accounting for systematic effects.