SIMPLE = T / file does conform to FITS standard
BITPIX = 32 / number of bits per data pixel
NAXIS = 0 / number of data axes
EXTEND = T / FITS dataset may contain extensions
COMMENT FITS (Flexible Image Transport System) format is defined in 'Astronomy
COMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H
DATE = '2003-04-23T00:00:00' /file creation date (YYYY-MM-DDThh:mm:ss UT)
OBJECT = 'ALL-SKY ' / Portion of sky given
COMMENT This is a composite all-sky map of neutral hydrogen column density
COMMENT (N_HI), formed from the Leiden/Dwingeloo HI survey data
COMMENT (Hartmann & Burton 1997) and the composite N_HI map of Dickey and
COMMENT Lockman (1990). The two datasets are not matched in sensitivity or
COMMENT resolution: note that discontinuities exist in the constructed
COMMENT composite map. A pixel mask is provided to indicate which dataset
COMMENT was used for each location on the sky.
COMMENT Hartmann & Burton provide a velocity integrated
COMMENT (-450 km/s < V_lsr < +400 km/s) HI brightness temperature map in
COMMENT Galactic coordinates, sampled every 0.5 degrees. This entire data set
COMMENT was converted to N_HI by multiplying by their factor of
COMMENT 1.8224e18 K km s-1 cm-2 and then interpolated to pixel centers
COMMENT appropriate for HEALPix Nside=512. Since the Leiden/Dwingeloo survey
COMMENT does not have sky coverage for declinations < -30 deg., the lower
COMMENT resolution Dickey & Lockman map was also interpolated to HEALPix and
COMMENT used to fill in the coverage gap. The Dickey & Lockman N_HI map is
COMMENT itself a composite of several surveys which had been merged and
COMMENT averaged onto 1 deg. bins in Galactic coordinates. Their map
COMMENT includes emission between -250 km/s < V_lsr < 250 km/s (excluding the
COMMENT LMC and SMC).
COMMENT The Leiden/Dwingeloo Survey data were obtained from the CDS.
COMMENT The Dickey & Lockman map was obtained from NCSA ADIL.
COMMENT This file is distributed and maintained by LAMBDA.
REFERENC= 'Legacy Archive for Microwave Background Data Analysis (LAMBDA) '
REFERENC= ' http://lambda.gsfc.nasa.gov/ '
REFERENC= 'Atlas of Galactic Neutral Hydrogen, '
REFERENC= 'Hartmann & Burton 1997 Cambridge University Press. '
REFERENC= 'HI in the Galaxy, Dickey & Lockman 1990 Ann. Rev. A&A, 28, 215. '
REFERENC= 'NCSA Astronomy Digital Image Library: http://adil.ncsa.uiuc.edu/ '
REFERENC= 'CDS: http://cdsweb.u-strasbg.fr/ '
REFERENC= 'HEALPix Home Page: http://www.eso.org/science/healpix/ '
FREQ = '21 cm ' / Frequency band
RESOLUTN= 9 / Resolution index
SKYCOORD= 'Galactic' / Coordinate system
PIXTYPE = 'HEALPIX ' / Pixel algorithm
ORDERING= 'NESTED ' / Ordering scheme
NSIDE = 512 / Resolution parameter
NPIX = 3145728 / # of pixels
FIRSTPIX= 0 / First pixel (0 based)
LASTPIX = 3145727 / Last pixel (0 based)
Archive Map Table
XTENSION= 'BINTABLE' /binary table extension
BITPIX = 8 /8-bit bytes
NAXIS = 2 /2-dimensional binary table
NAXIS1 = 8 /width of table in bytes
NAXIS2 = 3145728 /number of rows in table
PCOUNT = 0 /size of special data area
GCOUNT = 1 /one data group (required keyword)
TFIELDS = 2 /number of fields in each row
COMMENT *** End of mandatory fields ***
COMMENT *** Column names ***
TTYPE1 = 'TEMPERATURE' /label for field 1
COMMENT *** Column formats ***
TFORM1 = 'E ' /data format of field: 4-byte REAL
TUNIT1 = 'atoms cm-2' /physical unit of field
TTYPE2 = 'N_OBS ' /label for field 2
TFORM2 = 'E ' /data format of field: 4-byte REAL
TUNIT2 = 'counts ' /physical unit of field
EXTNAME = 'Archive Map Table' /name of this binary table extension
DATE = '2003-04-23T00:00:00' /Table creation date
PIXTYPE = 'HEALPIX ' /Pixel algorithm
ORDERING= 'NESTED ' /Ordering scheme
NSIDE = 512 /Resolution parameter
FIRSTPIX= 0 /First pixel (0 based)
LASTPIX = 3145727 /Last pixel (0 based)
COMMENT The TEMPERATURE field contains the N_HI column density map in units
COMMENT atoms cm-2.
COMMENT N_obs is set to 1 for those pixels for which Leiden/Dwingeloo survey
COMMENT data were available. The southern declinations filled in with the
COMMENT Dickey & Lockman data have N_obs set to 2.