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I. Introduction
The High Resolution IRAS Galaxy Atlas (IGA) is an atlas
of the far infrared emission (60 and 100 micron) from
Galactic Plane (-4.7 to +4.7 degrees galactic latitude)
plus the molecular clouds in Orion, Rho Oph and
Taurus-Auriga produced using data from the Infrared
Astronomical Satellite (IRAS). The IGA maps have 1'-2'
resolution and provide a ten-fold improvement in areal
information relative to the IRAS Sky Survey Atlas (ISSA).
However, unlike the ISSA, the IGA does not contain any 12
or 25 micron data. These wavelengths were not processed
as part of the generation of the IGA.
The IGA was developed under an Archival Data Processing
(ADP) grant from NASA with support from Infrared Processing
and Analysis Center (IPAC). The basic HIRES algorithm used
to develop the Atlas is
described in Aumann, H.H., Fowler, J.W., and Melnyk, M.,
1990 (A.J.,99, 1674). The modifications needed to run HIRES
on a parallel super-computer are described in Cao, Y.
Prince, T.A., Terebey, S., and Beichman, C.A., 1996, (PASP,
108, 535). The characteristics of the Atlas are given in
Cao, Y., Prince, T.A Terebey, S. Beichman, C.A., 1997,
(Ap.J., (Suppl.), in press). The latter two papers are
available in postscript form in this release as
TECHNICAL.ps and IGA.ps.
The IGA incorporates several important improvements from
standard HIRES processing at IPAC. Foremost is improved
destriping and zodiacal emission subtraction, which lead to
reduced artifacts, better ability to discern
low-surface-brightness features and the ability to mosaic
images without edge discontinuities. The IGA is well suited
to high-resolution studies of extended structure, and will
be valuable for a wide range of scientific studies,
including: the structure and dynamics of the interstellar
medium (ISM); cloud core surveys within giant molecular
clouds; detailed studies of HII regions and star-forming
regions; determination of initial mass functions (IMFs) of
massive stars; and study of supernova remnants (SNRs). The
IGA will be especially useful for multi-wavelength studies
using the many Galactic plane surveys that have similar
(1') resolution.
The IGA images consist of maps made with 1 or 20
iterations of the HIRES algorithm, corresponding to either
no non-linear processing (1 iteration), or to the maximum
amount (20 iterations) of non-linear processing deemed to
be reasonably free of artifacts. We emphasize that the
spatial resolution within the maps varies with the details
of the scan coverage for a particular area of the sky. The
beam maps provided with each field are essential for
assessing the angular resolution at various positions in
the maps. For more discussion of the quality of the maps,
the nature and number of artifacts, please see the two
articles by Cao et al. appended to this release.
II. Arrangement of IGA Images in this Release
The IGA is arranged as a series of 1.4x1.4 deg FITS images
(plates) on 1 deg centers with 15 arcsec pixels. Maps of
molecular clouds are 2.5 deg in size on 2 deg centers. The
IGA data are arranged on the tapes as
follows:
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Restore tapes 1 through 9 with command 'tar -xfb TAPEDEV
124' where TAPEDEV is the name of your 8mm tape device.
The directory structure on tapes 1 through 9 is as
follows:
TYPE/pPLATE_bBAND/img
where
TYPE is galactic_plane, orion, rho_oph or
taurus-auriga
PLATE is 4 digit IRAS plate number
BAND is 3 (60 micron) or 4 (100 micron)
The file naming convention is as follows:
In the TYPE/pPLATE_bBAND directory:
pPLATE[ge]LONLAT_bem_bBAND_fwhm.txt - estimated beam
sizes (FWHM)
for all spikes present in the beam
sample map (iteration 20 only)
In the TYPE/pPLATE_bBAND/img directory:
img_pPLATE[ge]LONLAT_bBAND_ITER.fits - intensity
map
img_pPLATE[ge]LONLAT_bem_bBAND_ITER.fits - beam sample
map
cfv_pPLATE[ge]LONLAT_bBAND_ITER.fits - correction factor
variance
phn_pPLATE[ge]LONLAT_bBAND_ITER.fits - photometric
noise
bem_pPLATE[ge]LONLAT_bBAND_20.fits - simulator input
"spike" and
background model for beam sample
cvg_pPLATE[ge]LONLAT_bBAND.fits - coverage
det_pPLATE[ge]LONLAT_bBAND.fits - detector track
where PLATE is 4 digit IRAS plate number
[ge] is g for galactic coordinates, e for equatorial
(clouds)
LON is 3 digit longitude of field center
LAT is [+-] and 2 digit latitude of field center
BAND is 3 (60 micron) or 4 (100 micron)
ITER is 1 or 20 for iteration number
Software and documentation are located on Tape 0 in
appropriately named directories.
The software catalog contains the besthires program that
will return the best field name given input coordinates.
The besthires program located in the software/bin directory
was compiled on a Sun IPX running Solaris. If this binary
file does not work on your machine, you must recompile the
C programs in the software/besthires directory via the
following procedure:
a) cd software/besthires
b) make all
c) make install
Please refer to file IGA.ps for a full explanation of
the atlas. TECHNICAL.ps deals with the technical aspects.
Refer to software/besthires/README for instructions on
running besthires. File 'field_centers' is an ASCII table
file that contains the TYPE catalog, IRAS plate number and
LON LAT center positions for all fields.
Additional information on the IGA can be found on the IPAC
homepage on the World Wide Web
(http://www.ipac.caltech.edu).
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