First light for the GRAVITY+ Adaptive Optics: Extreme adaptive optics for the Very Large Telescope Interferometer

Vol. 707
13. Astronomical instrumentation

First light for the GRAVITY+ Adaptive Optics: Extreme adaptive optics for the Very Large Telescope Interferometer

This must-read paper presents the next-generation infrared adaptive optics interferometric system GRAVITY+, now online at VLTI. The acquisition system (which uses natural and laser guide stars), the calibration steps and results, and the pipeline processing components are described in detail. This alone makes for essential reading, but the most remarkable results are the preliminary observational analyses of test targets that demonstrate the power of the new system. The promise of the instrument is shown with a range of targets that span the science case. The intrinsically most luminous quasar known at moderate redshifts, SMSS J052915.80-435152.0, was observed at redshifted Hbeta, showing that the broad line region is resolved and that the inferred radial velocity distribution is spatially resolved at about one parsec. Spectroscopy of the young giant planet HR 8799e permits the easy detection of a molecular band, in this case CO 2.3 microns, along with similar superb results for brown dwarfs and other very low-mass stellar objects. The pièce de résistance is the resolution of the innermost regions of the HL Tau accretion disk and the determination of the spatial orientation of the rotation axis of the debris disk that hosts star beta Pic.