An extended scattered light disk around AT Pyx

Possible planet formation in a cometary globule^★

¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
e-mail: c.ginski@uva.nl
² Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
³ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁴ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁵ Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS, UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
⁶ Universidad de los Andes, Mérida, Venezuela
⁷ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
⁹ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
¹⁰ Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
¹¹ Department of Astronomy, Stockholm University, 10691 Stockholm, Sweden
¹² CRAL, CNRS, Université Lyon 1, Université de Lyon, ENS, 9 avenue Charles Andre, 69561 Saint Genis Laval, France
¹³ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
¹⁴ Geneva Observatory, University of Geneva, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
¹⁵ University of Michigan, Astronomy Department, 1085 S. University Ave., Ann Arbor, MI 48109-1107, USA
¹⁶ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
¹⁷ DOTA, ONERA, Université Paris Saclay, 91123, Palaiseau France
¹⁸ NOVA Optical Infrared Instrumentation Group, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands

Received: 21 September 2021
Accepted: 21 November 2021

Abstract

Aims. To understand how the multitude of planetary systems that have been discovered come to be, we need to study systems at different evolutionary stages, with different central stars but also in different environments. The most challenging environment for planet formation may be the harsh UV radiation field of nearby massive stars which quickly erodes disks by external photo-evaporation. We observed the AT Pyx system, located in the head of a cometary globule in the Gum Nebula, to search for signs of ongoing planet formation.

Methods. We used the extreme adaptive optics imager VLT/SPHERE in Dual Beam Polarization Imaging Mode in H-band as well as in IRDIFS Extended mode (K12-band imaging and Y-H integral field spectroscopy) to observe AT Pyx in polarized light and total intensity. Additionally, we employed VLT/NACO to observe the system in the L-band.

Results. We resolve the disk around AT Pyx for the first time in scattered light across multiple wavelengths in polarized light and total intensity. We find an extended (≥126 au) disk, with an intermediate inclination of between 35° and 42°. The disk shows a complex substructure and we identify two or possibly three spiral-like features. Depending on the precise geometry of the disk (which we cannot unambiguously infer from our data), the disk may be eccentric with an eccentricity of ~0.16 or partially self-shadowed. The spiral features and possible eccentricity are both consistent with signatures of an embedded gas giant planet with a mass of ~1 M_Jup. Our own observations can rule out brown dwarf companions embedded in the resolved disk, but are nevertheless not sensitive enough to confirm or rule out the presence of a gas giant.

Conclusions. AT Pyx is the first disk to be spatially resolved in a cometary globule in the Gum Nebula. By comparison with disks in the Orion Nebula Cluster we note that the extension of the disk may be exceptional for this environment if the external UV radiation field is indeed comparable to other cometary globules in the region. The signposts of ongoing planet formation are intriguing and need to be followed up with either higher sensitivity or at different wavelengths.