Polarimetric differential imaging with VLT/NACO

A comprehensive PDI pipeline for NACO data (PIPPIN)^★

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands
e-mail: regt@strw.leidenuniv.nl
² School of Natural Sciences, Center for Astronomy, University of Galway, Galway H91 CF50, Ireland
³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
⁴ Instituto de Astrofísica, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. Fernandez Concha 700, Santiago, Chile
⁵ Núcleo Milenio de Formación Planetaria (NPF), Valparaiso, Chile
⁶ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
⁷ Department of Physics, Astronomy & Mathematics, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK
⁸ Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura 7630355, Santiago, Chile
⁹ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
¹⁰ Centro de Astrobiología (CAB), CSIC-INTA, ESAC Campus, Camino bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
¹¹ Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15–17, 1121 Budapest, Hungary
¹² CSFK, MTA Centre of Excellence, Konkoly-Thege Miklós út 15–17, 1121 Budapest, Hungary
¹³ ELTE Eötvös Loránd University, Institute of Physics and Astronomy, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
¹⁴ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁵ Department of Physics, University of California, Broida Hall, Santa Barbara, CA 93106, USA
¹⁶ Departamento de Fisica, Universidad de Santiago de Chile, Av. Victor Jara 3659, Santiago, Chile
¹⁷ Millennium Nucleus on Young Exoplanets and their Moons (YEMS), Santiago, Chile
¹⁸ Center for Interdisciplinary Research in Astrophysics and Space Exploration (CIRAS), Universidad de Santiago, Santiago 9170124, Chile
¹⁹ Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile

Received: 26 November 2023
Accepted: 19 February 2024

Abstract

Context. The observed diversity of exoplanets can possibly be traced back to the planet formation processes. Planet-disk interactions induce sub-structures in the circumstellar disk that can be revealed via scattered light observations. However, a high-contrast imaging technique such as polarimetric differential imaging (PDI) must first be applied to suppress the stellar diffraction halo.

Aims. In this work we present the PDI PiPelIne for NACO data (PIPPIN), which reduces the archival polarimetric observations made with the NACO instrument at the Very Large Telescope. Prior to this work, such a comprehensive pipeline to reduce polarimetric NACO data did not exist. We identify a total of 243 datasets of 57 potentially young stellar objects observed before NACO’s decommissioning.

Methods. The PIPPIN pipeline applies various levels of instrumental polarisation correction and is capable of reducing multiple observing setups, including half-wave plate or de-rotator usage and wire-grid observations. A novel template-matching method is applied to assess the detection significance of polarised signals in the reduced data.

Results. In 22 of the 57 observed targets, we detect polarised light resulting from a scattering of circumstellar dust. The detections exhibit a collection of known sub-structures, including rings, gaps, spirals, shadows, and in- or outflows of material. Since NACO was equipped with a near-infrared wavefront sensor, it made unique polarimetric observations of a number of embedded protostars. This is the first time detections of the Class I objects Elia 2-21 and YLW 16A have been published. Alongside the outlined PIPPIN pipeline, we publish an archive of the reduced data products, thereby improving the accessibility of these data for future studies.