Dusty debris disks around main-sequence stars are signposts for the existence of planetesimals and exoplanets. From cross-correlating Hipparcos stars with the IRAS catalogs, we identify 146 stars within 120 pc of Earth that show excess emission at 60 µm. This search took special precautions to avoid false positives.Our sample is reasonably well distributed from late B to early K-type stars, but it contains very few later type stars. Even though IRAS flew more than 20 years ago and many astronomers have cross-correlated its catalogs with stellar catalogs, we were still able to newly identify debris disks at as many as 33 main-sequence stars; of these, 32 are within 100 pc of Earth. The power of an all-sky survey satellite like IRAS is evident when comparing our 33 new debris disks with the total of only 22 dusty debris disk stars detected first with the more sensitive, but pointed, satellite ISO . Our investigation focuses on the mass, dimensions, and evolution of dusty debris disks.

We present the discovery of seven new T dwarfs identified in the Two Micron All Sky Survey. Low-resolution (R $ 150) 0.8-2.5 m spectroscopy obtained with the Infrared Telescope Facility (IRTF) SpeX instrument reveals the characteristic H 2 O and CH 4 bands in the spectra of these brown dwarfs. Comparison with spectral standards observed with the same instrument enables us to derive classifications of T3 to T7 for the objects in this sample. Moderate-resolution (R $ 1200) near-infrared spectroscopy for a subset of these discoveries reveal K i line strengths consistent with previously observed trends with spectral type. Follow-up imaging observations provide proper-motion measurements for these sources, ranging from less than 0B1 to 1B55 yr À1 . One object, 2MASS 0034+0523, has a spectrophotometric distance placing it within 10 pc of the Sun. This source also exhibits a depressed K-band peak reminiscent of the peculiar T dwarf 2MASS 0937+2931 and may be a metal-poor or old, high-mass brown dwarf. We also present low-resolution SpeX data for a set of M-and L-type dwarf, subdwarf, and giant comparison stars used to classify 59 additional candidates identified as background stars. These are primarily M5-M8.5 dwarfs, many exhibiting H i Pa , but include three candidate ultracool M subdwarfs and one possible early-type L subdwarf.

We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous submm imagery suggested the existence of the dust-depleted cavity at r ≤ 46 AU, our observations reveal the presence of scattered light components as close as 0. ′′ 2 (∼ 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0. ′′ 5 (∼ 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h ∼ 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations.

The past decade has seen a significant growth in research targeted at space-based observatories for imaging exosolar planets. The challenge is in designing an imaging system for high contrast. Even with a perfect coronagraph that modifies the point spread function to achieve high contrast, wavefront sensing and control is needed to correct the errors in the optics and generate a "dark hole." The high-contrast imaging laboratory at Princeton University is equipped with two Boston Micromachines Kilo-DMs. We review here an algorithm designed to achieve high contrast on both sides of the image plane while minimizing the stroke necessary from each deformable mirror (DM). This algorithm uses the first DM to correct for amplitude aberrations and uses the second DM to create a flat wavefront in the pupil plane. We then show the first results obtained at Princeton with this correction algorithm, and we demonstrate a symmetric dark hole in monochromatic light.

We present the discovery of a brown dwarf or possible planet at a projected separation of 1. 9 = 29 AU around the star GJ 758, placing it between the separations at which substellar companions are expected to form by core accretion (∼5 AU) or direct gravitational collapse (typically 100 AU). The object was detected by direct imaging of its thermal glow with Subaru/HiCIAO. At 10-40 times the mass of Jupiter and a temperature of 550-640 K, GJ 758 B constitutes one of the few known T-type companions, and the coldest ever to be imaged in thermal light around a Sun-like star. Its orbit is likely eccentric and of a size comparable to Pluto's orbit, possibly as a result of gravitational scattering or outward migration. A candidate second companion is detected at 1. 2 at one epoch.

We present first results from a major program of methane filter photometry for low-mass stars and brown dwarfs. The definition of a new methane filter photometric system is described. A recipe is provided for the differential calibration of methane imaging data using existing Two Micron All Sky Survey (2MASS) photometry. We show that these filters are effective in discriminating T dwarfs from other types of stars, and we demonstrate this with AngloAustralian Telescope observations using the IRIS2 imager. Methane imaging data and proper motions are presented for 10 T dwarfs identified as part of the 2MASS Wide-Field T Dwarf Search, seven of them initially identified as T dwarfs using methane imaging. We also present near-infrared moderate-resolution spectra for five T dwarfs newly discovered by this technique. Spectral types obtained from these spectra are compared to those derived from both our methane filter observations and spectral types derived by other observers. Finally, we suggest a range of future programs to which these filters are clearly well suited: the winnowing of T dwarf and Y dwarf candidate objects coming from the next generation of near-infrared sky surveys, the robust detection of candidate planetary-mass brown dwarfs in clusters, the detection of T dwarf companions to known L and T dwarfs via deep methane imaging, and the search for rotationally modulated time-variable surface features on cool brown dwarfs.

We report high-resolution 1.6 µm polarized intensity (P I) images of the circumstellar disk around the Herbig Ae star AB Aur at a radial distance of 22 AU (0. ′′ 15) up to 554 AU (3. ′′ 85),

We present 0. ′′ 1 resolution near-infrared integral field spectroscopy of Hα in a z=1.4781 star forming galaxy, Q2343-BM133. These observations were obtained with OSIRIS (OH Suppressing Infra-Red Imaging Spectrograph) using the W.M. Keck Observatory Laser Guide Star Adaptive Optics system. Hα emission is resolved over a 0. ′′ 8 (6.8 kpc) x 0. ′′ 5 (4.3 kpc) region with a 0. ′′ 1 spatial resolution. We find a global flux of 4.2±0.6×10 −16 ergs s −1 cm −2 , and detect a spatially resolved velocity gradient of ∼134 km s −1 across the galaxy and a global velocity dispersion of 73±9 km s −1 . An upper limit of [Nii]/Hα 0.12 is inferred, which implies that this galaxy is not dominated by an active galactic nucleus and has a metallicity at or below 1/2 solar metallicity. We derive a star formation rate (SFR) of 47±6 M ⊙ yr −1 , and a dereddened SFR of 66±9 M ⊙ yr −1 . Two-dimensional kinematics for Q2343-BM133 fit well with an inclined-disk model, with which we estimate an enclosed mass of 4.3×10 9 M ⊙ within 5.5 kpc. A possible merger scenario is also presented, and can not be fully ruled out. We derive a virial mass of 1.1×10 10 M ⊙ for a disk geometry, using the observed velocity dispersion. We propose that Q2343-BM133 is currently at an early stage of disk formation at a look-back time of 9.3 Gyr.