Abstract
Context. Planetary systems hold the imprint of the formation and of the evolution of planets especially at young ages, and in particular at the stage when the gas has dissipated leaving mostly secondary dust grains. The dynamical perturbation of planets in the dust distribution can be revealed with high-contrast imaging in a variety of structures. Aims. SPHERE, the high-contrast imaging device installed at the VLT, was designed to search for young giant planets in long period, but is also able to resolve fine details of planetary systems at the scale of astronomical units in the scattered-light regime. As a young and nearby star, NZ Lup was observed in the course of the SPHERE survey. A debris disk had been formerly identified with HST/NICMOS. Methods. We observed this system in the near-infrared with the camera in narrow and broad band filters and with the integral field spectrograph. High contrasts are achieved by the mean of pupil tracking combined with angular differential imaging algorithms. Results. The high angular resolution provided by SPHERE allows us to reveal a new feature in the disk which is interpreted as a superimposition of two belts of planetesimals located at stellocentric distances of ~85 and ~115 au, and with a mutual inclination of about 5°. Despite the very high inclination of the disk with respect to the line of sight, we conclude that the presence of a gap, that is, a void in the dust distribution between the belts, is likely. Conclusions. We discuss the implication of the existence of two belts and their relative inclination with respect to the presence of planets.
Highlights
Debris disks correspond to a late stage in the evolution of planetary systems when the primordial material has been expelled out of the systems or incorporated into planets and other bodies
The differences between models with gap(s), a smooth transition, or no gap at all are small because the mutual inclinations and the distances of the belts could mimic a gap in the scattered light image
Summary Here we summarize the results of our analysis on the NZ Lup debris disk. – The angular resolution and contrast achieved with SPHERE reveal a globally very inclined debris disk (∼85◦) with a disk splitting attributed to the presence of two noncoplanar planetesimal belts
Summary
Debris disks correspond to a late stage in the evolution of planetary systems when the primordial material has been expelled out of the systems or incorporated into planets and other bodies. Left to right columns: the date of observations in UT, the ID of the ESO program, the filters combination, the amount of field rotation in degrees, the individual exposure time (DIT) in seconds, the total number of exposures, the total exposure time in seconds, the DIMM seeing measured in arcseconds, the correlation time τ0 in milliseconds, and the true north (TN) offset in degrees This point source is not related to the system but is flagged as a background star While the images convey the idea that a second ring would be sitting on top (higher elevation from the star) of the main ring, one should consider that the actual distribution of dust is altered by the ADI process, and cross talks are to be expected for intricate geometry In any case, such a configuration would be difficult, if not impossible, to explain dynamically.
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