FITS Headers
wmap_ilc_rgn_defn_7yr_v4.fits
Primary Header
SIMPLE = T / file does conform to FITS standard BITPIX = 8 / 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 = '2009-12-16T00:00:00' /file creation date (YYYY-MM-DDThh:mm:ss UT) TELESCOP= 'WMAP ' /Wilkinson Microwave Anisotropy Probe OBJECT = 'ALL-SKY ' / Portion of sky given COMMENT This file defines the 12 sky regions (numbered 0-11) used to construct COMMENT the 7-year WMAP Internal Linear Combination (ILC) map. There are two COMMENT classes of region definition to be aware of: 1) the 12 disjoint COMMENT regions used to construct the map from a linear combination of the 5 COMMENT frequency band maps, and 2) the 12 nearly corresponding regions used COMMENT to compute the frequency weights. The N_OBS field in this map defines COMMENT the first set of regions. The value of the N_OBS field gives the COMMENT region to which that pixel belongs, and the corresponding frequency COMMENT weights used for each region are: COMMENT COMMENT Region K Ka Q V W COMMENT 0 0.1495 -0.7184 -0.3188 2.3071 -0.4195 COMMENT 1 -0.0035 -0.2968 -0.1963 2.0533 -0.5567 COMMENT 2 0.0258 -0.3368 -0.3162 1.8368 -0.2096 COMMENT 3 -0.0945 0.1772 -0.6087 1.5541 -0.0281 COMMENT 4 -0.0771 0.0881 -0.4149 0.9559 0.4480 COMMENT 5 0.1928 -0.7451 -0.4538 2.4673 -0.4612 COMMENT 6 -0.0918 0.1946 -0.5586 1.0227 0.4332 COMMENT 7 0.1533 -0.7464 -0.2033 2.2798 -0.4834 COMMENT 8 0.2061 -0.2979 -1.5705 3.5678 -0.9056 COMMENT 9 -0.0889 -0.1241 -0.0816 1.2066 0.0880 COMMENT 10 0.1701 -0.8610 -0.1825 2.8264 -0.9530 COMMENT 11 0.2358 -0.8467 -0.6020 2.8336 -0.6206 COMMENT COMMENT The above weights were determined by minimizing the variance of the COMMENT output map in a nearly corresponding region of the sky. Since these COMMENT latter regions are not disjoint, they are specified in the form of a COMMENT bit mask in the TEMPERATURE field of the map. Specifically, if a COMMENT pixel is used to compute the weights applied in region N, then a COMMENT unique bit value is set as follows: COMMENT COMMENT bit 0 set if used for computing region 0 wts; bit value = 1 COMMENT bit 1 set if used for computing region 1 wts; bit value = 2 COMMENT bit 2 set if used for computing region 2 wts; bit value = 4 COMMENT bit 3 set if used for computing region 3 wts; bit value = 8 COMMENT bit 4 set if used for computing region 4 wts; bit value = 16 COMMENT bit 5 set if used for computing region 5 wts; bit value = 32 COMMENT bit 6 set if used for computing region 6 wts; bit value = 64 COMMENT bit 7 set if used for computing region 7 wts; bit value = 128 COMMENT bit 8 set if used for computing region 8 wts; bit value = 256 COMMENT bit 9 set if used for computing region 9 wts; bit value = 512 COMMENT bit 10 set if used for computing region 10 wts; bit value = 1024 COMMENT bit 11 set if used for computing region 11 wts; bit value = 2048 COMMENT COMMENT For example, the set of pixels used to compute the weights for COMMENT region N may be obtained by performing the logical operation COMMENT Set = (INTEGER(TEMPERATURE) AND 2^N)/2^N COMMENT COMMENT See the WMAP Explanatory Supplement for further details. REFERENC= 'WMAP Explanatory Supplement: http://lambda.gsfc.nasa.gov/ RELEASE = 'DR4 ' / Release number VERSION = 'PASS 4 ' / Internal MAP Version 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) HISTORY This is actually the DR2 file with header updates; the same algorithm HISTORY was used for the DR4 version of the ILC. 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 TTYPE1 = 'TEMPERATURE' /label for field 1 TFORM1 = '1E ' /data format of field: 4-byte REAL TUNIT1 = 'counts ' /physical unit of field TTYPE2 = 'N_OBS ' /label for field 2 TFORM2 = '1E ' /data format of field: 4-byte REAL TUNIT2 = 'counts ' /physical unit of field EXTNAME = 'Archive Map Table' /name of this binary table extension DATE = '2009-12-16T00:00:00' /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 is a bitmask defining the set of pixels used to COMMENT compute the weights for each region. COMMENT N_obs defines the ILC regions 0-11 to which the weights are applied. END
