README File for the High Resolution IRAS Galaxy Atlas (IGA)

Infrared Processing and Analysis Center (IPAC)

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 and

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

  Tape 0:
and documentation
  Tape 1: Galactic Plane 1
plates 92 - 211
  Tape 2: Galactic Plane 2
plates 212 - 456
  Tape 3: Galactic Plane 3
plates 492 - 844
  Tape 4: Galactic Plane 4
plates 845 - 1234
  Tape 5: Galactic Plane 5
plates 1235 - 1519
  Tape 6: Galactic Plane 6
plates 1520 - 1639
  Tape 7: Orion
all plates
  Tape 8: Rho Oph
all plates
  Tape 9: Taurus-Auriga
all plates

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 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 for a full explanation of the atlas. 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 (