Foreground: HI Column Density

The data made available through this page have been superseded by the Effelsberg-Bonn HI survey and the GASS HI survey.
The Effelsberg-Bonn northern sky HI map is available here
and the HI4PI all-sky HI map made from a combination of Effelsberg-Bonn and GASS data is available here

The sky maps are generated using the HEALPix sky pixelization scheme. The first file listed for each map contains the data in its native HEALPix format. For the convenience of users who do not require the capabilities that HEALPix offers, we also provide the maps in two projected image formats: Mollweide and Zenith Equal Area (ZEA). These files contain the string "_mollweide" and "_zea" respectively, and may be displayed with standard astronomical display software such as DS9 and SAOImage. Note that the image pixels typically over-sample the HEALPix pixels, thus some amount of data replication will be present in the image data. As a result, care must be taken when using the image data in a regime where the noise properties are important since the statistical weight per pixel will also be replicated.

Recommended download procedure for '.fits' or '.tar.gz' files:
right click on the file name and save. For more information on the use of Dataset IDs,
see the LAMBDA Products Overview.

Dickey & Lockman HI Column Density
Dataset Id
File Info
File Name
Delivery Date
Composite N(HI) map
25 MB lambda_combined_nh.fits
Fits Header

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. Andrew F. Ptak
LAMBDA Director: Dr. Thomas M. Essinger-Hileman
NASA Official: Dr. Thomas M. Essinger-Hileman
Web Curator: Mr. Michael R. Greason