HIRES employs the Maximum Correlation Method (MCM) (H.H. Aumann, J.W. Fowler and M. Melnyk, 1990,AJ, 99,1674) to construct (resolution-enhanced) coadded images. HIRES images may be requested from IPAC using the e-mail based data request system.
There are some rules of thumb for choosing good HIRES targets. Often examination of the results of a HIRES request will suggest that the data would benefit from re-processing with slightly different processing options set. In this case, a new HIRES request for the revised processing can be submitted. Options which are not explicitly mentioned in the request form can be written in as "Special Instructions".
HIRES is a three-step process:
As of March 31, 1993, HIRES is AC calibrated. The IRAS detectors exhibited dwell-time dependent responsivity changes, especially at 12 µm. This is the IRAS data feature known as the "AC/DC effect". Previous IRAS image products have been calibrated on the DC scale, which is correct for structures on spatial scales greater than 30'. The AC scale gives flux densities commensurate with the Point Source Catalog (PSC2) for point sources.
HIRES Processing Defaults
The current defaults were chosen to provide the best performance (highest resolution, freedom from artifacts) for the majority of targets. They may not be the best choice for any given specific target!
Most of the defaults can be changed using various processing options which appear explicitly in the request form, or which may be added using the "Special Processing" field.
There are several diagnostic map types available from HIRES in addition to the surface brightness map. These ancillary maps are essential to the interpretation of the HIRES results. However, you can request that only some of the ancillary maps be produced.
The available maps and naming conventions are:
The following set of ASCII files is also produced:
In the names above:
Note: The default processing thus produces 76 maps for each field!
See the examples for more information and detailed descriptions of the HIRES output.
Artifacts in HIRES
HIRES is an excellent amplifier of the peculiarities of the IRAS data, in particular, you should be familiar with the AC/DC effect and point source tails.
HIRES images may suffer from any of a number of artifacts inconsistent with the actual appearance of the sky. Users should be aware of the common artifacts.
The HIRES usage notes give some insight into interpretation of HIRES results and possible re-processing you may wish to consider. Achieved resolution, mosaicking and the use of AOs are among the topics discussed.