D. S. Acton

We report on the first observation of cosmologically distant field galaxies with an high order Adaptive Optics (AO) system on an 8-10 meter class telescope. Two galaxies were observed at 1.6 microns at an angular resolution as high as 50 milliarcsec using the AO system on the Keck-II telescope. Radial profiles of both objects are consistent with those of local spiral galaxies and are decomposed into a classic exponential disk and a central bulge. A star-forming cluster or companion galaxy as well as a compact core are detected in one of the galaxies at a redshift of 0.37+/-0.05. We discuss possible explanations for the core including a small bulge, a nuclear starburst, or an active nucleus. The same galaxy shows a peak disk surface brightness that is brighter than local disks of comparable size. These observations demonstrate the power of AO to reveal details of the morphology of distant faint galaxies and to explore galaxy evolution.Comment: 5 pages, Latex, 3 figures. Accepted for publication in P.A.S.

The Michelson Doppler Imager (MDI) is a spectral imaging experiment on the ESA-NASA Solar and Heliospheric Observatory spacecraft (SOHO-see Domingo et al., 1995). SOHO was launched in December, 1995, and reached its final orbit about the Earth-Sun Lagrangian point L1 in mid-February, 1996. This point, about 1.5×l0⁶ km towards the Sun, is where the Earth’s and Sun’s gravity balance, allowing a nearly stable orbit ideal for continuous observations of the Sun and solar wind. MDI is collecting the observational data for the Solar Oscillations Investigation (SOI), a study of the interior structure of the Sun as inferred from the normal modes of oscillation seen on its surface (“heliosesmology”). Since launch, MDI has been collecting images showing the Doppler velocity, continuum intensity, and magnetic field on the solar surface with high spatial and temporal resolution. SOI/MDI were developed jointly by Stanford University and Lockheed Martin Advanced Technology Center, supported by NASA (see Scherrer et al., 1995). The Principal Investigator is Prof. P. Scherrer of Stanford.

The W. M. Keck Observatory and Lawrence Livermore National Labs are currently developing an adaptive optics system for use on Keck II--a 10.8-meter segmented telescope. This AO system will make use of a 349-actuator deformable mirror (DM). The Keck II telescope sits atop Hawaii’s Mauna Kea, where the ambient nighttime temperature varies between -5 and 5 degrees C. In order to reduce dome seeing, and to minimize the thermal emissivity, the AO system (and hence the DM) will be cooled to the ambient temperature of the outside air. Therefore, we are motivated to use actuators in the DM that are optimized for operation at 0 degrees C.

The sun is a bright, low-contrast, extended object. One arcsecond corresponds to 725 km on the sun. In the solar atmosphere the density scale height and the photon mean-free-path are both ~100 km. Due to the large conductivity, the solar magnetic field has an extremely inhomogenous structure with a typical scale of 100 km or even less. In order to resolve 50 km on the sun, a telescope should have an angular resolution of 0.07 arcsec. In the visible (λ=500 nm), this would require an aperture of about 2 m.