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We report on a superdense star-forming region with an effective radius (R e ) smaller than 13 pc identified at z=6.143 and showing a star-formation rate density Σ SF R ∼ 1000 M yr −1 kpc −2 (or conservatively > 300 M yr −1 kpc −2 ). Such a dense region is detected with S/N 40 hosted by a dwarf extending over 440 pc, dubbed D1. D1 is magnified by a factor 17.4(±5.0) behind the Hubble Frontier Field galaxy cluster MACS J0416 and elongated tangentially by a factor 13.2±4.0 (including the systematic errors). The lens model accurately reproduces the positions of the confirmed multiple images with a r.m.s. of 0.35 . D1 is part of an interacting star-forming complex extending over 800 pc. The SED−fitting, the very blue ultraviolet slope (β −2.5, F λ ∼ λ β ) and the prominent Lyα emission of the stellar complex imply that very young (< 10 − 100Myr), moderately dust-attenuated (E(B-V)<0.15) stellar populations are present and organised in dense subcomponents. We argue that D1 (with a stellar mass of 2 × 10 7 M ) might contain a young massive star cluster of M 10 6 M and M U V −15.6 (or m U V = 31.1), confined within a region of 13 pc, and not dissimilar from some local super star clusters (SSCs). The ultraviolet appearance of D1 is also consistent with a simulated local dwarf hosting a SSC placed at z=6 and lensed back to the observer. This compact system fits into some popular globular cluster formation scenarios. We show that future high spatial resolution imaging (e.g., E−ELT/MAORY-MICADO and VLT/MAVIS) will allow us to spatially resolve light profiles of 2-8 pc.

Background: Recent advances in technology have provided the opportunity for off-line analysis of digital video-clips of two-dimensional (2-D) echocardiographic images.

We have performed H and K S band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e, at H band for the first time. The H and K S magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d. We also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 M J for b and 7 M J for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 M J for HR 8799b, c, d, and e respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects.

We present diffraction-limited Ks band and L ′ adaptive optics images of the edge-on debris disk around the nearby F2 star HD 15115, obtained with a single 8.4 m primary mirror at the Large Binocular Telescope. At Ks band the disk is detected at signal-to-noise per resolution element (SNRE) ∼ 3-8 from ∼ 1-2. ′′ 5 (45-113 AU) on the western side, and from ∼ 1.2-2. ′′ 1 (63-90 AU) on the east. At L ′ the disk is detected at SNRE ∼ 2.5 from ∼ 1-1. ′′ 45 (45-90 AU) on both sides, implying more symmetric disk structure at 3.8 µm. At both wavelengths the disk has a bow-like shape and is offset from the star to the north by a few AU. A surface brightness asymmetry exists between the two sides of the disk at Ks band, but not at L ′ . The surface brightness at Ks band declines inside 1 ′′ (∼ 45 AU), which may be indicative of a gap in the disk near 1 ′′ . The Ks -L ′ disk color, after removal of the stellar color, is mostly grey for both sides of the disk. This suggests that scattered light is coming from large dust grains, with 3-10 µm-sized grains on the east side and 1-10 µm dust grains on the west. This may suggest that the west side is composed of smaller dust grains than the east side, which would support the interpretation that the disk is being dynamically affected by interactions with the local interstellar medium.

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The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl ( 75% at 2.16µm) near infrared narrowband (Brγ: 2.16µm and [FeII]: 1.64µm) images of 47 young (∼ 1 Myr) Orion Trapezium θ 1 Ori cluster members. The inner ∼ 41 × 53 ′′ of the 01 The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; cluster was imaged at spatial resolutions of ∼ 0.050 ′′ (at 1.64µm). A combination of high spatial resolution and high S/N yielded relative binary positions to ∼ 0.5 mas accuracies. Including previous speckle data, we analyze a 15 year baseline of high-resolution observations of this cluster. We are now sensitive to relative proper motions of just ∼ 0.3 mas/yr (0.6 km/s at 450 pc) this is a ∼ 7× improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the θ 1 Ori B 2 B 3 system of 4.9 ± 0.3 km/s and 7.2 ± 0.8 km/s in the θ 1 Ori A 1 A 2 system (with correlations of PA vs. time at > 99% confidence). All five members of the θ 1 Ori B system appear likely as a gravitationally bound "mini-cluster". The very lowest mass member of the θ 1 Ori B system (B 4 ; mass ∼ 0.2M ⊙ ) has, for the first time, a clearly detected motion (at 4.3 ± 2.0 km/s; correlation=99.7%) w.r.t B 1 . However, B 4 is most likely in an long-term unstable (non-hierarchical) orbit and may "soon" be ejected from this "mini-cluster". This "ejection" process could play a major role in the formation of low mass stars and brown dwarfs.

The Large Binocular Telescope (LBT) is a unique telescope featuring two co-mounted optical trains with 8.4m primary mirrors. The telescope Adaptive Optics (AO) system uses two innovative key components, namely an adaptive secondary mirror with 672 actuators and a high-order pyramid wave-front sensor. During the on-sky commissioning such a system reached performances never achieved before on large ground-based optical telescopes. Images with 40mas resolution and Strehl Ratios higher than 80% have been acquired in H band (1.6 μm). Such images showed a contrast as high as 10 -4 . Based on these results, we compare the performances offered by a Natural Guide Star (NGS) system upgraded with the state-of-the-art technology and those delivered by existing Laser Guide Star (LGS) systems. The comparison, in terms of sky coverage and performances, suggests rethinking the current role ascribed to NGS and LGS in the next generation of AO systems for the 8-10 meter class telescopes and Extremely Large Telescopes (ELTs).