README File for the Extended IRAS Galaxy Atlas (EIGA)

Infrared Processing and Analysis Center (IPAC)
June 2003

I. Introduction

The Extended IRAS Galaxy Atlas (EIGA) is an extension of the original IGA to b = 6.7° along a portion of the Galactic plane. High resolution images at 60 um and 100 um have been produced to match the latitude coverage of radio continuum observations obtained as part of the Canadian Galactic Plane Survey (CGPS).

IGA images were incorporated into the Canadian Galactic Plane Survey as a far-infrared data set to complement the radio continuum and molecular line data. Since the IGA has a high-latitude cutoff of b=4.7° the initial CGPS mosaics constructed using the IGA had a blank strip at high latitudes. In order to match the infrared coverage of the CGPS with the radio continuum coverage a high-latitude extension (to b = 6.7°) of the IGA was constructed covering approximately 75° < l < 148°

The basic HIRES algorithm used to develop the EIGA is described in Aumann, Fowler, & Melnyk 1990 (AJ,99, 1674). The EIGA was constructed using the computer facilities at the Canadian Institute for Theoretical Astrophysics at the University of Toronto. Unlike the IGA, a non-parallel version of the HIRES code was used. The characteristics of the EIGA are given in Kerton & Martin 2000 (ApJS, 126, 85).

The EIGA 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 EIGA 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 EIGA will be especially useful for multi-wavelength studies using the many Galactic plane surveys that have similar (1') resolution.

The EIGA 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 Kerton & Martin 2000 (ApJS, 126, 85).

The EIGA is arranged as a series of 1.4x1.4 deg FITS images (plates) on 1 deg centers with 15 arcsec pixels.