HIivo://CDS/P/HICDSCDS2011-02-14T12:00:00Z2019-05-05T06:29:00ZCDS Helpdeskcds-question@unistra.frSky surveyRadio astronomyH I line emissionComposite all-sky map of neutral hydrogen column density (N_HI), formed from the Leiden/Dwingeloo HI survey data (Hartmann & Burton 1997) and the composite N_HI map of Dickey and Lockman (1990). The two datasets are not matched in sensitivity or resolution: note that discontinuities exist in the constructed composite map. A pixel mask is provided to indicate which dataset was used for each location on the sky. Hartmann & Burton provide a velocity integrated (-450 km/s %3C V_lsr %3C +400 km/s) HI brightness temperature map in Galactic coordinates, sampled every 0.5 degrees. This entire data set was converted to N_HI by multiplying by their factor of 1.8224e18 K km s-1 cm-2 and then interpolated to pixel centers appropriate for HEALPix Nside=512. Since the Leiden/Dwingeloo survey does not have sky coverage for declinations %3C -30 deg., the lower resolution Dickey & Lockman map was also interpolated to HEALPix and used to fill in the coverage gap. The Dickey & Lockman N_HI map is itself a composite of several surveys which had been merged and averaged onto 1 deg. bins in Galactic coordinates. Their map includes emission between -250 km/s %3C V_lsr %3C 250 km/s (excluding the LMC and SMC). The Leiden/Dwingeloo Survey data were obtained from the CDS. The Dickey & Lockman map was obtained from NCSA ADIL. This original HEALPix file is distributed and maintained by LAMBDA.Original acknowledgement for data: We acknowledge the use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA), part of the High Energy Astrophysics Science Archive Center (HEASARC). HEASARC/LAMBDA is a service of the Astrophysics Science Division at the NASA Goddard Space Flight Center.1990ARA&A..28..215Dhttps://alasky.cds.unistra.fr/HISurveyResearchIsDerivedFromHEASARC/LAMBDAThis HiPS is distributed under ODbL license by Unistra/CNRShttps://alasky.cds.unistra.fr/HIhttps://alaskybis.cds.unistra.fr/HI44239 478929.45926598642347e-25 9.45926598642347e-25https://alasky.cds.unistra.fr/HI/Moc.fitsRadio