README File for the Mid-Infrared IRAS Galaxy Atlas (MIGA)

Last Updated: Sept 2003

I. Introduction

The Mid-Infrared Galaxy Atlas (MIGA) is a mid-infrared (12 µm and 25 µm) counterpart to the far-infrared IRAS Galaxy Atlas (IGA). It was originally intended to provide a mid-infrared data set for the Canadian Galactic Plane Survey (CGPS), however as radio surveys of the Milky Way continue to expand their coverage additional images will be added to the MIGA.

The basic HIRES algorithm used to develop the MIGA is described in Aumann, Fowler, & Melnyk 1990 (AJ,99, 1674). The MIGA 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 MIGA are given in Kerton & Martin 2000 (ApJS, 126, 85).

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

The MIGA 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 MIGA is arranged as a series of 1.4x1.4° FITS images on 1° centers with 15" pixels.