Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.

Spatially resolved scattered-light images of circumstellar debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, the systemic architectures, and forces perturbing the starlight-scattering circumstellar material. Using HST/STIS broadband optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in a sample of ten circumstellar debris systems, and one "mature" protoplanetrary disk all with HST pedigree, using PSF-subtracted multi-roll coronagraphy. These observations probe stellocentric distances > 5 AU for the nearest systems, and simultaneously resolve disk substructures well beyond corresponding to the giant planet and Kuiper belt regions within our own Solar System.They also disclose diffuse very low-surface brightness dust at larger stellocentric distances.Herein we present new results inclusive of fainter disks such as HD92945 (F disk /F star = 5x10 -5 ) confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like sub-structures and significant asymmetries and complex morphologies include: HD181327 for which we posit a spray of ejecta from a recent massive collision in an exo-Kuiper belt; HD61005 suggested to be interacting with the local ISM; HD15115 and HD32297, discussed also in the context of putative environmental interactions. These disks, and HD15745, suggest that debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk we find out-of-plane surface brightness asymmetries at > 5 AU that may implicate the existence of one or more planetary perturbers. Time resolved images of the MP Mus proto-planetary disk provide spatially resolved temporal variability in the disk illumination. These and other new images from our HST/STIS GO/12228 program enable direct inter-comparison of the architectures of these exoplanetary debris systems in the context of our own Solar System.

We present new coronagraphic images of b Pictoris obtained with the Space Telescope Imaging Spectrograph (STIS) in 1997 September. The high-resolution images clearly detect the circumstellar (0A .1) disk as close to the star as corresponding to a projected radius of 15 AU. The images deÐne the 0A .75, warp in the disk with greater precision and at closer radii to b Pic than do previous observations. They show that the warp can be modeled by the projection of two components : the main disk and a fainter component, which is inclined to the main component by 4¡È5¡ and extends only as far as B4A from the star. We interpret the main component as arising primarily in the outer disk and the tilted component as deÐning the inner region of the disk. The observed properties of the warped inner disk are inconsistent with a driving force from stellar radiation. However, warping induced by the gravitational potential of one or more planets is consistent with the data. Using models of planet-warped disks constructed by Larwood & Papaloizou, we derive possible masses of the perturbing object.

We present Hubble Space Telescope (HST ) spectroscopy of the nucleus of M31 obtained with the Space Telescope Imaging Spectrograph (STIS). Spectra that include the Ca ii infrared triplet (k ' 8500 8) see only the red giant stars in the double brightness peaks P1 and P2. In contrast, spectra taken at k ' 3600 5100 8 are sensitive to the tiny blue nucleus embedded in P2, the lower surface brightness nucleus of the galaxy. P2 has a K-type spectrum, but we find that the blue nucleus has an A-type spectrum: it shows strong Balmer absorption lines. Hence, the blue nucleus is blue not because of AGN light but rather because it is dominated by hot stars. We show that the spectrum is well described by A0 giant stars, A0 dwarf stars, or a 200 Myr old, single-burst stellar population. White dwarfs, in contrast, cannot fit the blue nucleus spectrum. Given the small likelihood for stellar collisions, recent star formation appears to be the most plausible origin of the blue nucleus. In stellar population, size, and velocity dispersion, the blue nucleus is so different from P1 and P2 that we call it P3 and refer to the nucleus of M31 as triple.Because P2 and P3 have very different spectra, we can make a clean decomposition of the red and blue stars and hence measure the light distribution and kinematics of each uncontaminated by the other. The line-of-sight velocity distributions of the red stars near P2 strengthen the support for Tremaine's eccentric disk model. Their wings indicate the presence of stars with velocities of up to 1000 km s À1 on the anti-P1 side of P2.The kinematics of P3 are consistent with a circular stellar disk in Keplerian rotation around a supermassive black hole. If the P3 disk is perfectly thin, then the inclination angle i ' 55 is identical within the errors to the inclination of the eccentric disk models for P1+P2 by Peiris & Tremaine and by Salow & Statler. Both disks rotate in the same sense and are almost coplanar. The observed velocity dispersion of P3 is largely caused by blurred rotation and has a maximum value of ¼ 1183 AE 201 km s À1 . This is much larger than the dispersion ' 250 km s À1 of the red stars along the same line of sight and is the largest integrated velocity dispersion observed in any galaxy. The rotation curve of P3 is symmetric around its center. It reaches an observed velocity of V ¼ 618 AE 81 km s À1 at radius 0B05 ¼ 0:19 pc, where the observed velocity dispersion is ¼ 674 AE 95 km s À1 . The corresponding circular rotation velocity at this radius is $1700 km s À1 . We therefore confirm earlier suggestions that the central dark object interpreted as a supermassive black hole is located in P3.Thin-disk and Schwarzschild models with intrinsic axial ratios b/a P 0:26 corresponding to inclinations between 55 and 58 match the P3 observations very well. Among these models, the best fit and the lowest black hole mass are obtained for a thin-disk model with M ¼ 1:4 ; 10 8 M . Allowing P3 to have some intrinsic thickness and considering possible systematic errors, the 1 confi...

Coronagraphic imaging with the Space Telescope Imaging Spectrograph on board the Hubble Space T elescope reveals a D450 AU radius circumstellar disk around the Herbig Ae star HD 163296. A broadband (0.2È1.0 km) reÑected light image shows the disk oriented at a position angle of 140¡^5¡ and inclined to our line of sight by D60¡^5¡. The disk includes an annulus of reduced scattering at 325 AU and exhibits a Ñat trend of surface brightness in to 180È122 AU consistent with a cleared (1A .5È1A), central zone. For r º 370 AU the disk surface brightness drops as r to the approximately [3.5 power. The disk cannot be traced beyond 450 AU in our data. The disk is accompanied by a chain of nebulosities at compatible with detection of a Herbig-Haro Ñow. The HD 163296 disk most P.A.\42¡ .5^3¡ .5, closely resembles the disk of HD 141569. As in the HD 141569 system, the dynamical e †ects of a planet may be necessary to explain the structure in the outer disk.