Damien Gratadour

A Giant Planet Imaged in the Disk of the Young Star β Pictoris

Planet Is Born The 10-million-year-old star β Pictoris, has long been suspected to host a planet. Through images obtained with the Very Large Telescope, an array of four telescopes located in Chile, Lagrange et al. (p. 57, published online 10 June) now confirm the presence of a young, giant planet, β Pictoris b, orbiting within the dusty disk that surrounds the star. β Pictoris b orbits closer to its star than Uranus and Neptune do to the Sun in our solar system. This orbital separation is consistent with the in situ formation of the planet via a core accretion mechanism. Thus, giant planets can form within a stellar dust disk in only a few million years. The Very Large Telescope reveals that a huge planet formed within a star’s dusty disk in a few million years. Here, we show that the ~10-million-year-old β Pictoris system hosts a massive giant planet, β Pictoris b, located 8 to 15 astronomical units from the star. This result confirms that gas giant planets form rapidly within disks and validates the use of disk structures as fingerprints of embedded planets. Among the few planets already imaged, β Pictoris b is the closest to its parent star. Its short period could allow for recording of the full orbit within 17 years.

Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

The Gemini multiconjugate adaptive optics system (GeMS) at the Gemini South telescope in Cerro Pachon is the first sodium-based multilaser guide star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near-infrared, with uniform quality over a field of view of two square arcminutes. This paper is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light.

MOAO first on-sky demonstration with CANARY

Context. A new challenging adaptive optics (AO) system, called multi-object adaptive optics (MOAO), has been successfully demonstrated on-sky for the first time at the 4.2 m William Herschel Telescope, Canary Islands, Spain, at the end of September 2010. Aims. This system, called CANARY, is aimed at demonstrating the feasibility of MOAO in preparation of a future multi-object near infra-red (IR) integral field unit spectrograph to equip extremely large telescopes for analysing the morphology and dynamics of high-z galaxies. Methods. CANARY compensates for the atmospheric turbulence with a deformable mirror driven in open-loop and controlled through a tomographic reconstruction by three widely separated off-axis natural guide star (NGS) wavefront sensors, which are in open loop too. We compared the performance of conventional closed-loop AO, MOAO, and ground-layer adaptive optics (GLAO) by analysing both IR images and simultaneous wave-front measurements. Results. In H-band, Strehl ratios of 0.20 are measured with MOAO while achieving 0.25 with closed-loop AO in fairly similar seeing conditions (r 0 ≈ 15 cm at 0.5 μm). As expected, MOAO has performed at an intermediate level between GLAO and closed-loop AO.

First on-sky SCAO validation of full LQG control with vibration mitigation on the CANARY pathfinder

Adaptive optics provides real time correction of wavefront disturbances on ground based telescopes. Optimizing control and performance is a key issue for ever more demanding instruments on ever larger telescopes affected not only by atmospheric turbulence, but also by vibrations, windshake and tracking errors. Linear Quadratic Gaussian control achieves optimal correction when provided with a temporal model of the disturbance. We present in this paper the first on-sky results of a Kalman filter based LQG control with vibration mitigation on the CANARY instrument at the Nasmyth platform of the 4.2-m William Herschel Telescope. The results demonstrate a clear improvement of performance for full LQG compared with standard integrator control, and assess the additional improvement brought by vibration filtering with a tip-tilt model identified from on-sky data, thus validating the strategy retained on the instrument SPHERE at the VLT.

Open-loop tomography with artificial neural networks on CANARY: on-sky results

We present recent results from the initial testing of an artificial neural network (ANN)-based tomographic reconstructor Complex Atmospheric Reconstructor based on Machine lEarNing (CARMEN) on CANARY, an adaptive optics demonstrator operated on the 4.2m William Herschel Telescope, La Palma. The reconstructor was compared with contemporaneous data using the Learn and Apply (L&A) tomographic reconstructor. We find that the fully optimized L&A tomographic reconstructor outperforms CARMEN by approximately 5percent in Strehl ratio or 15nm rms in wavefront error. We also present results for CANARY in Ground Layer Adaptive Optics mode to show that the reconstructors are tomographic. The results are comparable and this small deficit is attributed to limitations in the training data used to build the ANN. Laboratory bench tests show that the ANN can outperform L&A under certain conditions, e.g. if the higher layer of a model two layer atmosphere was to change in altitude by ∼300m (equivalent to a shift of approximately one tenth of a subaperture).

High angular resolution K -band spectroscopy of the nucleus of NGC 1068 with PUEO-GRIF (CFHT)

We provide new high angular resolution K-band spectroscopic observations of the nucleus of NGC 1068 obtained with the new 3-D spectrograph GriF coupled to PUEO, the CFHT adaptive optics system. Results match well with the general framework of the unified model of active galactic nuclei (AGN) and bring more precise evaluation of the size and structure of the close AGN environment. The K-band emission is dominated by the thermal continuum of the compact central source (albeit resolved: FWHM 0:12 00 ) with a color temperature around 950 K (reddened sublimation temperature of the dust, corresponding to 1200 K when deredenned), interpreted as the border of a sublimation cavity within the dust torus, surrounding the central core. Coronal emission lines ((Sivi), (Sivii) and (Caviii)) are detected from a few tenths of arcseconds around this compact source and a new (Sivi) emission spot is found at 0.7 00 north of the central source. The Brackett emission features a very broad component (FWHM= 2500 km s 1 ) in the central 200 mas and we claim that it correponds to the broad line region seen through the dust. A narrower component (FWHM= 1600 km s 1 ) is seen at larger angular distance and is likely the trace of the narrow line region. Molecular hydrogen emission lines are detected beyond 0.6 00 of the central source. We interpret the lack of emission in the center as a lack of excited molecular H 2 along the line of sight, because of the putitative dust torus shading gas from UV photons. No evidence of stellar activity in a 1 00 radius around the central source can be found. We also compare these observations to the results of a numerical model of a torus harboring an active galactic nucleus. The main characteristics of the observed spectra (slope, flux) match well with the unified scheme of AGN, in the case of a dense (V= 40) obscuring torus containing silicate grains with an inclination angle of around 22 with regards to the line of sight.

GeMS: first on-sky results

GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results.

Near-infrared adaptive optics dissection of the core of NGC 1068 with NAOS-CONICA

We present an update analysis of recent near-infrared adaptive optics observations of NGC 1068 obtained with NAOS-CONICA at VLT/UT4. Ks, Land Mbands images were deconvolved using MISTRAL, a regularized algorithm based on a maximum a posteriori estimation of the object. Two regularization methods, one including a new maximum likelihood estimation of the object Power Spectral Density, and an edge preserving one, have been tested and converge to consistent results. The deconvolved images show a coherent evolution of the IR emission from 2.2 to 4.8µm. Deconvolution brings new elements: a) it strengthens the very peculiar nature of the four parallel elongated nodules previously discovered along the jet, which appear unresolved perpendicular to their long axis; b) it underlines the strong correlation between UV clouds and IR features, and c) it provides a more accurate multi-wavelength registration of the actual active nucleus. The overall aspect of the central 1 �� ×1 �� IR emission seems to point to the jet as a major mechanism to shape the NLR. For each identified structure, we derive a color temperature now based on three bands (M, L and K), before and after deconvolution, confirming the need for clumps of dust at unexpectedly high and almost constant temperature (about 500 K) up to 70 pc north of the nucleus. We explore several mechanisms to explain the color temperature and show that shocks, induced for instance by the interaction of the jet with a giant cloud, is unlikely to be the dominating mechanism to heat the dust. We detail our model of transient heating of Very Small Grains and show that it can provide a consistent explanation of the K, L, M colors and their lack of variation with distance when 0.6 nm diamond-like grains are heated by 4 to 8 eV UV photons. However, we do not exclude the possibility that part of the excitation could come from shocks. At Ks, deconvolution reinforces the previous claim that the central core is partially resolved along the N-S direction: the best fit to our data is an elliptical Gaussian extended along PA = −16 with a 2.1 pc FWHM along this direction. This result agrees with the predictions of the radiative transfer model we previously developed to interpret the spectroscopic behavior at K, and is consistent with VLTI/VINCI measurements. Several questions are raised by this study: a) is the jet dominant in shaping the NLR of this AGN? b) what is the real state of the dust in the environment of the core; c) is the simple doughnut torus model able to explain IR emission of the central source with a morphology that appears increasingly complex at small scale?

Four quadrant phase mask K -band coronagraphy of NGC 1068 with NAOS-CONICA at VLT

We observed the nucleus of NGC 1068 at Ks with NAOS-CONICA on the VLT, using the new four quadrant phase mask coronagraph that we recently developed. As the K-band emission is dominated by an intense compact central source, previous K-band adaptive optics images were severely affected by the limited exposure time and by scattered light in the immediate vicinity of the source. Thanks to the use of this new type of coronagraph coupled to adaptive optics, the complex dust structure near the central core is becoming observable at a resolution of 0.07 �� . North of the nucleus, an elongated, bending structure, and a series of four elongated and well aligned knots, superposable on the same pattern previously observed by us at 3.8 and 4.8 µm are well identified. This agrees with our first interpretation that, given the direction they align in, these knots may trace shocks induced in the ISM by the passage of the jet, very close to its origin. Moreover, precise relative photometry supports our interpretation of very small dust grains transiently heated by UV photons of the central source. To the South we detect a new group of filamentary structures, distributed in a cone at about 150 pc from the core. They might trace the redshifted southern narrow line region, seen through the dust. Finally, on larger scale (within a radius of three hundred pc) the source has an overall biconical shape whose angle matches well with the bicone observed in the UV-visible.

ATLAS: the E-ELT laser tomographic adaptive optics system

ATLAS is a generic Laser Tomographic AO (LTAO) system for the E-ELT. Based on modular, relatively simple, and yet innovative concepts, it aims at providing diffraction limited images in the near infra-red for a close to 100 percent sky coverage.