Foreground Data


Product Name
HI4PI HI Column Density
Coord. System
Projection Type
HEALPix, ring, res 10 (Nside=1024)


The HI 4-PI Survey (HI4PI) is a 21-cm all-sky survey of neutral atomic hydrogen. It is constructed from the Effelsberg-Bonn HI Survey (EBHIS), made with the 100-m radio telescope at Effelsberg/Germany, and the Galactic All-Sky Survey (GASS), observed with the Parkes 64-m dish in Australia. HI4PI comprises HI line emission from the Milky Way. This dataset is the atomic neutral hydrogen (HI) column density map derived from HI4PI (|Vlsr| < 600 km/s).

The survey data is available in a FITS binary extension table, ordered according to the HEALPix scheme. Each record in the table has the following fields:

* HPXINDEX  HEALPix index (nside=1024, RING scheme, 0-based)
* RA2000 Right Ascension (J2000) in degrees
* DEC2000Declination (J2000) in degrees
* GLONGalactic Longitude in degrees
* GLATGalactic Latitude in degrees
* NHI HI Column Density in cm-2


Argelander-Institut für Astronomie (AIfA), Max-Planck-Institut für Radioastronomie (MPIfR), and CSIRO/Australia


Permission is granted for publication and reproduction of this material for scientific and educational purposes. When using data products provided in this release, it is requested that authors refer to the HI4PI publication. We also ask that publications making use of these data include the following acknowledgement: "The Parkes Radio Telescope is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. The EBHIS data are based on observations performed with the 100-m telescope of the MPIfR at Effelsberg. EBHIS was funded by the Deutsche Forschungsgemeinschaft (DFG) under the grants KE757/7-1 to 7-3."

Frequency1420 MHz
CoverageAll sky
Bandpass1417.5 - 1423.5 MHz
Sensitivity2.3 x 1018 cm-2
ReferenceHI4PI Collaboration et al., AA 594, A116, 2016

Back to Product Page

A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason