High-contrast study of the candidate planets and protoplanetary disk around HD 100546^★

¹ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122, Padova, Italy
e-mail: elena.sissa@oapd.inaf.it
² Dipartimento di Fisica e Astronomia – Universita’ di Padova, Vicolo dell’Osservatorio 3, 35122, Padova, Italy
³ Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
⁴ Departamento Física Teórica, Universidad Autonóma de Madrid, Módulo 15, Facultad de Ciencias, Campus de Cantoblanco, 28049, Madrid, Spain
⁵ Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
⁶ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388, Marseille, France
⁷ University of Atacama, Copayapu 485, Copiapo, Chile
⁸ CRAL, UMR 5574, CNRS, Université de Lyon, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07, France
⁹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁰ Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹² INAF – Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy
¹³ Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁴ LESIA, Observatoire de Paris-Meudon, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, 5 Place Jules Janssen, 92195 Meudon, France
¹⁵ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
¹⁶ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
¹⁷ Unidad Mixta Internacional Franco-Chilena de Astronomia, CNRS/INSU UMI 3386 and Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
¹⁸ Observatoire de Genéve, University of Geneva, 51 Chemin des Maillettes, 1290, Versoix, Switzerland
¹⁹ INAF – Osservatorio Astronomico di Brera, via Emilio Bianchi 46, 23807, Merate (LC), Italy
²⁰ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via E. Bassini 15, 20133 Milano, Italy
²¹ Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden
²² European Southern Observatory, Karl-Schwarzschild-Str. 2, D85748 Garching, Germany
²³ Laboratoire Lagrange (UMR 7293), UNSA, CNRS, Observatoire de la Côte d’Azur, Bd. de l’Observatoire, 06304 Nice Cedex 4, France
²⁴ Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Avenue, Ann Arbor, MI 48109, USA

Received: 21 November 2017
Accepted: 30 August 2018

Abstract

The nearby Herbig Be star HD 100546 is known to be a laboratory for the study of protoplanets and their relation with the circumstellar disk, which is carved by at least two gaps. We observed the HD 100546 environment with high-contrast imaging exploiting several different observing modes of SPHERE, including data sets with and without coronagraphs, dual band imaging, integral field spectroscopy and polarimetry. The picture emerging from these different data sets is complex. Flux-conservative algorithm images clearly show the disk up to 200 au. More aggressive algorithms reveal several rings and warped arms that are seen overlapping the main disk. Some of these structures are found to lie at considerable height over the disk mid-plane at about 30 au. Our images demonstrate that the brightest wings close to the star in the near side of the disk are a unique structure, corresponding to the outer edge of the intermediate disk at ~ 40 au. Modeling of the scattered light from the disk with a geometrical algorithm reveals that a moderately thin structure (H∕r = 0.18 at 40 au) can well reproduce the light distribution in the flux-conservative images. We suggest that the gap between 44 and 113 au spans between the 1:2 and 3:2 resonance orbits of a massive body located at ~ 70 au, which mightcoincide with the candidate planet HD 100546b detected with previous thermal infrared (IR) observations. In this picture, the two wings can be the near side of a ring formed by disk material brought out of the disk at the 1:2 resonance with the same massive object. While we find no clear evidence confirming detection of the planet candidate HD 100546c in our data, we find a diffuse emission close to the expected position of HD 100546b. This source can be described as an extremely reddened substellar object surrounded by a dust cloud or its circumplanetary disk. Its astrometry is broadly consistent with a circular orbital motion on the disk plane, a result that could be confirmed with new observations. Further observations at various wavelengths are required to fully understand the complex phenomenology of HD 100546.