M81 as photographed from the Spitzer Space Telescope (formerly SIRTF) in the infrared light.

Observations of M81 were taken with the Spitzer Space Telescope (SST) during instrument commissioning to highlight the capabilities of the Multiband Imaging Photometry (MIPS) and Infrared Array Camera (IRAC) instruments. The SST images resolve this classic grand design spiral galaxy at impressive resolution and depth for the first time.

These images give a taste of what the SST will do for our undestanding of galaxies and galaxy evolution. M81 is part of the SIRTF Nearby Galaxies Survery (SINGS) Legacy program. SINGS will observe a total of 75 galaxies with all three SST science instruments. The SINGS team (lead by Robert Kennicutt) kindly allowed M81 to be imaged with MIPS and IRAC as part of the SST Early Release Observations.

This three-panel mosaic is a series of images obtained with the multiband imaging photometer. Thermal infrared emission at 24 microns (top), 70 microns (center) and 160 microns (bottom) is shown in the images. Note that the effective spatial resolution degrades as ones moves to longer wavelengths.

At these wavelengths, Spitzer sees the dust, rather than the stars, within the disc of silicates and carbonaceous grains. It is well-mixed with gas, which is best seen at radio wavelengths, to form the essential ingredients for future star formation.

Multiwavelength composite image of M81.

Visible-light comparison of M81. Credit: N.A. Sharp (NOAO/AURA/NSF)

3.6-micron image of M81.

8-micron image of M81.

24-micron image of M81.

The MIPS images were taken by a team composed for Karl Gordon, Chad Engelbracht, Almudena Alonso-Herroro, Pablo Perez-Gonzalez, George Rieke, Karl Misselt, Marcia Rieke, Robert Kennicutt, and Joannah Hinz all located at the University of Arizona. The IRAC images were taken by a team composed of Steve Willner, Matthew Ashby, Pauline Barmby, Giovanni Fazio, and Michael Pahre all located at the Harvard-Smithsonian Center for Astrophysics. Additional members of the wider M81 ERO team include George Helou, Philip Appleton, David Frayer, Susan Stolovy, and Lisa Storrie-Lombardi all located at the SIRTF Science Center/Infrared Processing Center, Caltech.

Credit for the Spitzer images: NASA/JPL-Caltech/K. Gordon (University of Arizona) & S. Willner (Harvard-Smithsonian Center for Astrophysics)
Credit for the NOAO comparison image: N.A. Sharp (NOAO/AURA/NSF)

Image series in different parts of the spectrum

---

Hartmut Frommert
Christine Kronberg
[contact]

Last Modification: 19 Dec 2003