The wavelength region of interest for studying important physical processes tends to fall outside the domain accessible with ground-based telescopes. This applies to both the mid-IR and the space-UV. Past generations of space instruments could not afford the resolution required by the relevant astrophysical spatial scales. The IR in particular suffered from this shortcoming, as the IRAS mission had very limited spatial resolution, and fully panchromatic SED studies were restricted to the spatially integrated light.
With ISO and Spitzer, we have entered a new era. Panchromatic imagery of
M81 over six decades in wavelength space is shown in
Fig. 14
([14]).
The proximity of M81 has made it a favorite target for many
investigations of galaxy properties from the X-ray to radio. Many
well-resolved images have been taken in the past, with the notable
exception of the IR. Previously, well-resolved far-IR images of galaxies
have only been possible for Local Group galaxies such as the Magellanic
Clouds. With the successful launch of Spitzer, it is now possible to map
many large galaxies in the far-IR with good spatial resolution, good
sensitivity, and in a reasonable amount of time. M81 is one of the key
galaxies in the Spitzer Infrared Nearby Galaxies Survey
([14]).
Two of the questions that can be probed with these new observations are
the variation of star-formation indicators and the IR-radio correlation
across the disk of M81. MIPS, Spitzer's mid-IR imager, permits
comparisons with UV and H
images to probe the behaviors of the IR,
H, and UV star-formation
indicators across M81. Such comparisons have been made for
global galaxy fluxes
([20]),
but rarely has it been possible to resolve all three indicators in a
single galaxy. By studying their resolved behavior, we will greatly
improve the accuracy of these star formation indicators for both
resolved and global galaxy measurements.
 |
Figure 14. Panchromatic view of M81 using
Spitzer, UIT, and ground-based images at wavelengths
of 1500 Å, 2500 Å,
H |