High resolution near-infrared imaging with tip-tilt adaptive optics

The development and design of the first operational tip-tilt Cassegrain secondary mirror are presented. This system, FASTTRAC, samples image motion at up to 50 Hz by tracking either infrared (m{dollar}rmsb{lcub}k{rcub}{dollar} {dollar}leq{dollar} 11) or visible (m{dollar}rmsb{lcub}R{rcub}{dollar} {dollar}leq{dollar} 16) guide stars up to 30" and 90" away from the science target respectively. The Steward Observatory 2.3m or 1.5m telescope secondaries act as rapid tip-tilt mirrors to stabilize image motion ({dollar}leq{dollar}0.1" rms;{dollar}sim{dollar}5 Hz {dollar}-{dollar}3 dB frequency) based on the motion of the guide star. FASTTRAC obtains nearly diffraction-limited resolutions in seeing conditions where D/r{dollar}sbcirc{dollar} {dollar}<{dollar} 4 in agreement with theoretical expectations.; FASTTRAC's unique ability to guide on infrared stars has allowed the first adaptively corrected images of the heavily extincted Galactic Center to be obtained. Over a hundred excellent (0.28" {dollar}<{dollar} FWHM {dollar}<{dollar} 0.6") images have been obtained of this region. These images do not detect any long term variations in the massive black hole candidate Sgr A*'s luminosity from June 1993 to September 1995. The average infrared magnitudes observed are K = 12.1 {dollar}pm{dollar} 0.3, H = 13.7 {dollar}pm{dollar} 0.3 and J = 16.6 {dollar}pm{dollar} 0.4 integrated over 0.5" at the position of Sgr A*. No significant rapid periodicities were observed from Sgr A* for amplitudes {dollar}geq{dollar}50% of the mean flux in the period range of 3-30 minutes. It is confirmed in the latest 0.28" FWHM image that there is 0.5" "bar" of emission running East-West at the position of Sgr A* as was earlier seen by Eckart et al. 1993.; The observed fluxes are consistent with an inclined accretion disk around a {dollar}sim{dollar}1 {dollar}times{dollar} 10{dollar}sp6{dollar} M{dollar}sbodot{dollar} black hole. However, they are also explained by a line of hot luminous (integrated luminosity of {dollar}sim{dollar}10{dollar}sp{lcub}3.5-4.6{rcub}{dollar}L{dollar}sbodot{dollar}) central cluster stars positionally coincident with Sgr A* naturally explaining the observed 0.5" "bar".; High-resolution images with FASTTRAC guiding on a faint (R = 16) visible guide star, combined with spectra from the MMT, have shown that IRAS FSC 10214 + 4724 (z = 2.28) gains its uniquely large luminosity of {dollar}sim{dollar}1.2 {dollar}times{dollar}10{dollar}sp{lcub}14{rcub}{dollar}h{dollar}sp{lcub}-2{rcub}{dollar}l{dollar}sbodot{dollar} by gravitational lensing magnification from a nearby (1.25" away) galaxy. The detection of a tentative 4000 A continuum break at 5690 {dollar}pm{dollar} 90 A indicates that this lensing galaxy has a redshift of 0.42 {dollar}pm{dollar} 0.02. A simple lensing model predicts that 10214 + 4724 is a "normal" background ultraluminous IR galaxy with an intrinsic (unlensed) luminosity of {dollar}sim{dollar}3.7 {dollar}times{dollar} 10{dollar}sp{lcub}12{rcub}{dollar}h{dollar}sp{lcub}-2{rcub}{dollar}L{dollar}sbodot{dollar}.