read_fits_cut4

This IDL facility reads a cut sky HEALPix map from a FITS file according to the HEALPix convention. The format used for the FITS file follows the one used for Boomerang98 and is adapted from COBE/DMR. This routine can also be used to read polarized cut sky map, where each Stokes parameter is stored in a different extension of the same FITS file.

Location in HEALPix directory tree: src/idl/fits/read_fits_cut4.pro 

FORMAT

IDL> READ_FITS_CUT4 , File, Pixel, Signal[, N_Obs, Serror, EXTENSION=, HDR=, XHDR=, NSIDE=, ORDERING=, COORDSYS=, HELP=]

QUALIFIERS

File

name of a FITS file in which the map is to be written

Pixel

(OUT, LONG vector),
index of observed (or valid) pixels

Signal

(OUT, FLOAT vector),
value of signal in each observed pixel

N_Obs

(OUT, LONG or INT vector, Optional),
number of observation per pixel

Serror

(OUT, FLOAT vector, Optional),
rms of signal in pixel. For white noise, this is $\propto 1/\sqrt{{\rm n\_obs}}$

KEYWORDS

EXTENSION=

(IN, optional),
0 based number of extension to read. Extension 0 contains the temperature information, while extensions 1 and 2 contain respectively the Q and U Stokes parameters related information. default:0

HDR=

(OUT, optional),
String array containing the primary header.

XHDR=

(OUT, optional),
String array containing the extension header.

NSIDE=

(OUT, optional),
returns on output the HEALPix resolution parameter, as read from the FITS header. Set to -1 if not found

ORDERING=

(OUT, optional),
returns on output the pixel ordering, as read from the FITS header. Either 'RING' or 'NESTED' or ' ' (if not found).

COORDSYS=

(OUT, optional),
returns on output the astrophysical coordinate system used, as read from FITS header (value of keywords COORDSYS or SKYCOORD)

HELP=

(IN, optional),
if set, an extensive help is displayed, and no file is read

DESCRIPTION

For more information on the FITS file format supported in HEALPix, including the one implemented in read_fits_cut4 , see https://healpix.sourceforge.io/data/examples/healpix_fits_specs.pdf.

RELATED ROUTINES

This section lists the routines related to read_fits_cut4

idl

version 6.4 or more is necessary to run read_fits_cut4

write_fits_cut4

This HEALPix IDL facility can be used to generate the FITS format cut-sky maps complient with HEALPix convention and readable by read_fits_cut4 .

read_fits_cut4, read_fits_partial, read_fits_map

read_tqu, read_fits_s

HEALPix IDL routines to read cut-sky maps and partial maps, full-sky maps, polarized full-sky maps and arbitrary data sets from FITS files

sxpar

This IDL routine (included in HEALPix package) can be used to extract FITS keywords from the header(s) HDR or XHDR read with read_fits_cut4 .