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The nearby E0 galaxy M87 in the Virgo Cluster contains one of the nearest examples of a powerful non-thermal jet source. In addition, HST spectroscopy of its nucleus give strong evidence for the presence of a ≈3×109 M⊙ central black hole (corresponding to Schwarzschild radius Rs∼0.0004 pc). These two facts together make M87 the best possible target for studying the initial jet formation and collimation process. Herein we report new 43 GHz VLBI observations of the nucleus of this galaxy, which clearly show the jet opening angle expanding rapidly as one approaches the core on scales ∼0.01 pc. We believe we have, for the first time, imaged the initial collimation region of a powerful extragalactic jet. We find significant collimation occurring on scales of 30–100 Rs, and argue this is consistent with expectations for poloidal collimation by a rotating accretion disk.

Over the course of the 3 day meeting, attendees reviewed the current states of the art in adaptive optics (AO) and optical interferometry (OI) and investigated the synthesis of these techniques that will be necessary for the next-generation of high angular resolution optical and IR telescopes. Given this motivation, what better keynote speaker to have than Nobel Laureate, Professor Charles Townes (University of California at Berkeley)? Untrammeled by overhead displays or gadgetry, Professor Townes simply unfolded the histories of the fields to the audience, here and there elucidating a point with typically understated (or even oblique) accounts of his own significant contributions. Of course, laser technology, which Professor Townes made possible, is the major tool for alignment and characterization of optical systems. Without this, AO and OI would not be where it is today. Professor Virginia Trimble (University of California at Irvine and University of Maryland) followed Professor Townes with a provocative talk: “provocative” on two accounts—the first, her eclectic wish list of what to do with the next generation of high-resolution instruments, and the second, galvanizing the attendees into singing (we think it was singing) the adaptive optics/optical interferometry battle hymn. Professor Roger Angel (Steward Observatory and University of Arizona) outlined the reasons why OI is essential for the detection of extrasolar planets. Proposed schemes stem from the original Bracewell and McPhie nulling interferometer concept. Some space-borne interferometer concepts were presented (DARWIN, OASES). Professor Angel discussed strategies for dealing with the zodiacal clouds in other systems; such clouds will be at least 10 times brighter than the extrasolar planets. The Large Binocular Telescope will be a test bed for some of the technical concepts. That instrument will see first light around 2002 and can be used as a Bracewell interferometer. The reasons why adaptive optics systems are needed for

The results of polarimetric λλ6,4 cm VLBA observations of the inner 5pc of the jet and core of Vir A (3C274, J1230+1223) are reported. At λ4 cm, the core and the inner parsec are unpolarized and there is evidence for ordered magnetic fields and large RM gradients at larger distances.

Massive galaxies often are the source of well collimated jets of material that flow outwards for tens to hundreds of kiloparsecs from the regions surrounding the presumed black holes at their centres. The processes by which the jets are formed and collimated have been important problems for many years1, and observations have hitherto had insufficient spatial resolution to investigate the length scales associated with these processes2,3. Here we report observations at 43 GHz of the inner regions of the nearby active galaxy M87. The data show a remarkably broad jet having an ‘opening angle’ of ∼60° near the centre, with strong collimation of the jet occurring at ∼30–100 Schwarzschild radii (rS) from the black hole: collimation continues out to ∼1,000 rS. These results are consistent with the hypothesis that jets are formed by an accretion disk around the central black hole, which is threaded by a magnetic field4.

We present new U, B, R, and H I imagery of the Virgo Cluster giant elliptical galaxy NGC 4472 and its interacting dwarf companion galaxy UGC 7636. Using a composite image reconstruction technique, we show that a trail of debris approx. 5 arcmin in length and approx. 1 arcmin in width (30x6 kpc for a Virgo cluster distance of 20 Mpc) is projected northward from the dwarf galaxy. A cloud of H I is projected along the northwest edge of the debris between the dwarf and gE. The dwarf's nuclear morphology is irregular and bow-shaped on what appears to be its leading edge. Apart from a number of isolated blue regions, most of of the trailing debris is similar in color to the dwarf's nucleus. Only a modest enhancement of star formation appears to have been induced by the interaction. Although separated by 15 kpc, the H I and stellar morphologies are remarkably similar. The stars and H I appear to have been tidally distorted in situ, prior to the cloud's removal by ram pressure. If the H I has maintained its shape by magnetic support, a magnetic field strength an order of magnitude larger than the galaxy's is required. Ram pressure deceleration due to the cloud's motion through NGC 4472's x-ray-emitting interstellar medium shold be sufficient for the cloud to become gravitationally bound to NGC 4472. The H I cloud is not self-gravitating and may fragment and be destroyed in the interaction. UGC 7636 will probably be disrupted by NGC 4472's strong tidal forces; the stellar debris will disperse into the Virgo cluster or become bound to NGC 4472's halo on eccentric orbits. The debris captured in the collision will have a negligible impact on NGC 4472's stellar and gaseous content. On the other hand, if similar interactions are common in giant elliptical galaxies, they could alter or deplete surrounding dwarf galaxy populations, fuel bursts of nuclear activity, and perhaps provide a source of magnetic energy to their interstellar media.