FITS Headers
lambda_combined_nh.fits
Primary Header
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) END
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 COMMENT *** End of mandatory fields *** COMMENT COMMENT COMMENT *** Column names *** COMMENT TTYPE1 = 'TEMPERATURE' /label for field 1 COMMENT COMMENT *** Column formats *** COMMENT 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. END
