D. S. Acton’s research while affiliated with University of California, Los Angeles and other places

The Keck Interferometer (KI) combined the two 10m W. M. Keck Observatory telescopes on Mauna Kea, Hawaii, as a long-baseline near- and mid-infrared interferometer. Funded by NASA, it operated from 2001 until 2012. KI used adaptive optics on the two Keck telescopes to correct the individual wavefronts, as well as active fringe tracking in all modes for path-length control, including the implementation of cophasing to provide long coherent integration times. KI implemented high sensitivity fringe-visibility measurements at H (1.6m), K (2.2m), and L (3.8m) bands, and nulling measurements at N band (10m), which were used to address a broad range of science topics. Supporting these capabilities was an extensive interferometer infrastructure and unique instrumentation, including some additional functionality added as part of the NSF-funded ASTRA program. This paper provides an overview of the instrument architecture and some of the key design and implementation decisions, as well as a description of all of the key elements and their configuration at the end of the project. The objective is to provide a view of KI as an integrated system, and to provide adequate technical detail to assess the implementation. Included is a discussion of the operational aspects of the system, as well as of the achieved system performance. Finally, details on V-2 calibration in the presence of detector nonlinearities as applied in the data pipeline are provided.

We report on observations obtained with the adaptive optics system at the 10 m Keck II Telescope during engineering validation and early science observing time for the adaptive optics system. We observed Neptune at near-infrared wavelengths. Angular resolution was 005–006, corresponding to a spatial scale of approximately 1000 km at Neptune. We discuss the latitudinal structure of circumferential cloud bands and of compact infrared-bright features seen in the southern hemisphere, as well as their variation with wavelength. We determine the values of I/F (proportional to the ratio of reflected intensity to incident solar flux) in the J and H infrared-wavelength bands, including narrowband filters where there is strong methane absorption. We use the I/F values inside and outside of methane bands to estimate the altitude of clouds responsible for the brightest compact features in the infrared. Our data show that, on two of our four observing dates, the brightest region on Neptune contained highly reflective haze layers located below the tropopause but not deeper than a few bars.

A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10-m or Lick 3-m, and direct images or AO images are sensitive to a wider field, extending to 10" or 38", depending upon the camera. One of the binary systems -- HD 114762 -- was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system -- Tau Boo -- was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target -- 16 Cyg B -- was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the Tau Boo binary contains an extremely close planet in a tidally-circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU.

This paper presents diffraction-limited 1-18 micron images of the young quadruple star system HD 98800 obtained with the W. M. Keck 10-m telescopes using speckle and adaptive optics imaging at near-IR wavelengths and direct imaging at mid-IR wavelengths. The two components of the visual binary, A and B, both themselves spectroscopic binaries, were separable at all wavelengths, allowing us to determine their stellar and circumstellar properties. Combining these observations with spectroscopic data from the literature, we derive an age of 10 Myr, masses of 0.93 and 0.64 M_sun and an inclination angle of 58 deg for the spectroscopic components of HD 98800 B, and an age of 10 Myr and a mass of 1.1 M_sun for HD 98800 Aa. Our data confirm that the large mid-IR excess is entirely associated with HD 98800 B. This excess exhibits a black body temperature of 150 K and a strong 10 micron silicate emission feature. The theoretical equilibrium radius of large, perfectly absorbing, 150 K grains around HD 98800 B is 2.4 AU, suggesting a circum-spectroscopic binary distribution. Our observations set important upper limits on the size of the inner dust radius of ~2 AU (mid-IR data) and on the quantity of scattered light of <10% (H-band data). For an inner radius of 2 AU, the dust distribution must have a height of at least 1 AU to account for the fractional dust luminosity of \~20% L_B. Based on the scattered light limit, the dust grains responsible for the excess emission must have an albedo of <0.33. The presence of the prominent silicate emission feature at 10 microns implies dust grain radii of >2 microns. The total mass of the dust, located in a circumbinary disk around the HD 98800 B, is >0.002 M_earth. The orbital dynamics of the A-B pair are likely responsible for the disk geometry. Comment: 27 pages, 4 tables, 9 figures; small revisions to section 3.2.4

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.P

Adaptive optics (AO) is a technology that corrects in real time for the blurring effects of atmospheric turbulence, in principle allowing Earth-bound telescopes to achieve their diffraction limit and to ``see'' as clearly as if they were in space. The power of AO using natural guide stars has been amply demonstrated in recent years on telescopes up to 3-4 m in diameter. The next breakthrough in astronomical resolution was expected to occur with the implementation of AO on the new generation of large, 8-10 m diameter telescopes. In this paper we report the initial results from the first of these AO systems, now coming on line on the 10 m diameter Keck II Telescope. The results include the highest angular resolution images ever obtained from a single telescope (0.022" and 0.040" at 0.85 and 1.65 mum wavelengths, respectively), as well as tests of system performance on three astronomical targets.

We present diffraction-limited images of the young quadruple star system HD 98800 obtained with the W. M. Keck 10-m telescopes from 1-18 microns using speckle imaging and adaptive optics imaging in the near-infrared, and direct imaging with OSCIR in the mid-infrared. These measurements are the first to resolve the 0.8'' (38 AU) North-South pair at multiple wavelengths through the silicate feature. The emission from HD 98800 A, a single-lined spectroscopic binary, is consistent with a Kurucz model photosphere of temperature 4500 K and luminosity 0.71 Lsun. In contrast, the emission seen in HD 98800 B, a double-lined spectroscopic binary, is fit by a Kurucz model photosphere of 4000 K with L = 0.58 Lsun, and a large mid-infrared to sub-millimeter excess with L = 0.11 Lsun. A black body fit to the excess emission yields a dust temperature of 150 K; there is also a strong 10 micron silicate emission feature. The equilibrium radius of this dust is 2.6 AU, indicating a circum-spectroscopic binary distribution of grains. The very high fractional luminosity of the dust, 0.2 LB, implies a large vertical component to the distribution, possibly a result of dynamical interactions with the central binary. This research was supported by the NASA Origins of Solar Systems program and the Packard Foundation.

The expected breakthrough in astronomical resolution with the implementation of Adaptive Optics (AO) on the new generation of large, 8-10 m diameter telescopes was clearly demonstrated in February, 1999 with the Natural Guide Star AO facility on the Keck II telescope. These first light images had a full-width-at-half-maximum of 0.04 arcsec at H-band and Strehl ratios up to 30 wavelength. Since first-light we have been engaged in a program to characterize and optimize the system on the sky while carrying out a program to verify the scientific capabilities. The facility is now available to our science community. The purpose of this paper is to provide a brief overview of the facility and its performance. Several science papers in this conference, ranging from planets to galaxies, will further demonstrate the dramatic new scientific capabilities of this facility.

We will review the status of the natural/laser guide star adaptive optics facility that is being constructed for the Keck II telescope.

Closed loop wave front correction of low order Zernike polynomials has been demonstrated using a phase diversity wavefront sensor. The Lockheed-Martin Advanced Technology Center phase diversity brassboard was used to demonstrate low bandwidth correction of aberrations consisting of the Zernike polynomials describing focus, coma and spherical. The method of Lofdahl-Scharmer is used to estimate and correct fixed aberrations in an optical system. The General Regression Neural Network method is used to estimate slowly varying aberrations in the same optical system. Closed loop experimental results from these tests are presented.