Protoplanetary disks in K_s-band total intensity and polarized light^★,★★

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
e-mail: bin.ren@oca.eu
² Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique (IPAG), 38000 Grenoble, France
³ Department of Astronomy, California Institute of Technology, MC 249-17, 1200 E California Blvd, Pasadena, CA 91125, USA
⁴ School of Natural Sciences, University of Galway, University Road, Galway H91 TK33, Ireland
⁵ Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA
⁶ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
⁷ Department of Astronomy, University of Florida, Gainesville, FL 32611, USA
⁸ Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
⁹ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
¹⁰ Indian Institute of Astrophysics, Koramangala 2nd Block, Bangalore 560034, India
¹¹ Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹² European Southern Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago, Chile

Received: 4 July 2023
Accepted: 12 October 2023

Abstract

Context. The diverse morphology among protoplanetary disks may result from planet-disk interactions, suggesting the presence of planets undergoing formation. The characterization of disks can provide information on the formation environments of planets. To date, most imaging campaigns have probed the polarized light from disks, which is only a fraction of the total scattered light and not very sensitive to planetary emission.

Aims. We aim to observe and characterize protoplanetary disk systems in the near-infrared in both polarized and total intensity light to carry out an unprecedented study of the dust scattering properties of disks, as well as of any possible planetary companions.

Methods. Using the star-hopping mode of the SPHERE instrument at the Very Large Telescope, we observed 29 young stars hosting protoplanetary disks and their reference stars in the K_s-band polarized light. We extracted disk signals in total intensity by removing stellar light using the corresponding reference star observations, by adopting the data imputation concept with sequential non-negative matrix factorization (DI-sNMF). For well-recovered disks in both polarized and total intensity light, we parameterized the polarization fraction phase functions using a scaled beta distribution. We investigated the empirical DI-sNMF detectability of disks using logistic regression. For systems with SPHERE data in the Y, J, and H bands, we have summarized their polarized color at an approximately 90° scattering angle.

Results. We obtained high-quality disk images in total intensity for 15 systems and in polarized light for 23 systems. The total intensity detectability of disks primarily depends on the host star brightness, which determines adaptive-optics control ring imagery and thus stellar signals capture using DI-sNMF. The peak of polarization fraction tentatively correlates with the peak scattering angle, which could be reproduced using certain composition for compact dust, yet more detailed modeling studies are needed. Most of the disks are blue in polarized J – K_s color and the fact that they are relatively redder as stellar luminosity increases indicates larger scatterers.

Conclusions. High-quality disk imagery in both total intensity and polarized light allows for disk characterizations in the polarization fraction. Combining these techniques reduces the confusion between the disk and planetary signals.