read_fits_map

This IDL facility reads in a HEALPix map from a FITS file.

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

FORMAT

IDL> READ_FITS_MAP , File, T_sky, [Hdr, Exthdr, PIXEL=, SILENT=, NSIDE=, ORDERING=, COORDSYS=, EXTENSION=, HELP=]

QUALIFIERS

File

name of a FITS file containing the HEALPix map in an extension or in the image field

T_sky

variable containing on output the HEALPix map

Hdr

(optional),
string variable containing on output the FITS primary header

Exthdr

(optional),
string variable containing on output the FITS extension header

PIXEL=

(optional),
pixel number to read from or pixel range to read (in the order of appearance in the file), starting from 0.
if $\ge$ 0 scalar : read from pixel to the end of the file
if two elements array : reads from pixel[0] to pixel[1] (included)
if absent : read the whole file

NSIDE=

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

ORDERING=

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

COORDSYS=

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

EXTENSION=

(optional),
extension unit to be read from FITS file: either its 0-based ID number (ie, 0 for first extension after primary array) or the case-insensitive value of its EXTNAME keyword. If absent, all available extensions are read.

KEYWORDS

HELP=

if set, an extensive help is displayed and no file is read

SILENT=

if set, no message is issued during normal execution

DESCRIPTION

read_fits_map reads in a HEALPix sky map from a FITS file, and outputs the variable T_sky, where the optional variables Hdr and Exthdr contain respectively the primary and extension headers. According to HEALPix convention, the map should be is stored as a FITS file binary table extension. Note:the routine read_tqu which requires less memory is recommended when reading large polarized maps.

RELATED ROUTINES

This section lists the routines related to read_fits_map

idl

version 6.4 or more is necessary to run read_fits_map

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 Exthdr read with read_fits_map.

synfast

This HEALPix facility will generate the FITS format sky map that can be read by read_fits_map.

write_fits_map

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

EXAMPLE:

read_fits_map, 'planck100GHZ-LFI.fits', map, hdr, xhdr, /silent

read_fits_map reads in the file 'planck100GHZ-LFI.fits' and outputs the HEALPix map in map, the primary header in hdr and the extension header in xhdr.