HI4PI: a full-sky H i survey based on EBHIS and GASS^⋆

¹ Argelander-Institut für Astronomie (AIfA), University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
² Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany
³ Department of Physics and Astronomy, University of Alabama, PO Box 870324, Tuscaloosa, AL, 35487-0324, USA
⁴ National Radio Astronomy Observatory, PO Box 2, Green Bank, WV, 24944, USA
⁵ CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia
⁶ Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
⁷ E. A. Milne Centre for Astrophysics, University of Hull, Hull, HU6 7RX, UK
⁸ Tartu Observatory, 61602 Tõravere, Tartumaa, Estonia
⁹ International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
¹⁰ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
¹¹ Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, Australia
¹² Graduate School of Science and Engineering, Kagoshima university, 1-21-35 Korimoto, 890-0065 Kagoshima, Japan
¹³ Institute of Space and Astronautical Science, Japan Aerospace Exploring Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
¹⁴ SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK
¹⁵ Department of Physics and Astronomy, West Virginia University, PO Box 6315, Morgantown, WV 26506, USA
¹⁶ ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia

^** Corresponding author: B. Winkel, e-mail: bwinkel@mpifr.de, P. M. W. Kalberla, e-mail: kalb@astro.uni-bonn.de

Received: 24 June 2016
Accepted: 7 September 2016

Abstract

Context. Measurement of the Galactic neutral atomic hydrogen (H i) column density, N_{H i}, and brightness temperatures, T_B, is of high scientific value for a broad range of astrophysical disciplines. In the past two decades, one of the most-used legacy H i datasets has been the Leiden/Argentine/Bonn Survey (LAB).

Aims. We release the H i 4π survey (HI4PI), an all-sky database of Galactic H i, which supersedes the LAB survey.

Methods. The HI4PI survey is based on data from the recently completed first coverage of the Effelsberg-Bonn H i Survey (EBHIS) and from the third revision of the Galactic All-Sky Survey (GASS). EBHIS and GASS share similar angular resolution and match well in sensitivity. Combined, they are ideally suited to be a successor to LAB.

Results. The new HI4PI survey outperforms the LAB in angular resolution (ϑ_FWHM = 16́́.2) and sensitivity (σ_rms = 43 mK). Moreover, it has full spatial sampling and thus overcomes a major drawback of LAB, which severely undersamples the sky. We publish all-sky column density maps of the neutral atomic hydrogen in the Milky Way, along with full spectroscopic data, in several map projections including HEALPix.