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A Circumplanetary Disk Around PDS70 C

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A Circumplanetary Disk Around PDS70 C Draft version July 21, 2021 Typeset using LATEX twocolumn style in AASTeX63 A Circumplanetary Disk Around PDS70 c Myriam Benisty ,1, 2 Jaehan Bae ,3, ∗ Stefano Facchini ,4 Miriam Keppler ,5 Richard Teague ,6 Andrea Isella ,7 Nicolas T. Kurtovic ,5 Laura M. Perez´ ,8 Anibal Sierra ,8 Sean M. Andrews ,6 John Carpenter ,9 Ian Czekala ,10, 11, 12, 13 Carsten Dominik ,14 Thomas Henning ,5 Francois Menard ,2 Paola Pinilla ,5, 15 and Alice Zurlo 16, 17 1Unidad Mixta Internacional Franco-Chilena de Astronom´ıa,CNRS, UMI 3386. Departamento de Astronom´ıa,Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile 2Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France 3Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA 4European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany 5Max Planck Institute for Astronomy, K¨onigstuhl 17, 69117, Heidelberg, Germany 6Center for Astrophysics Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA j 7Department of Physics and Astronomy, Rice University, 6100 Main Street, MS-108, Houston, TX 77005, USA 8Departamento de Astronom´a,Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile 9Joint ALMA Observatory, Avenida Alonso de C´ordova 3107, Vitacura, Santiago, Chile 10Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802, USA 11Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802, USA 12Center for Astrostatistics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802, USA 13Institute for Computational & Data Sciences, The Pennsylvania State University, University Park, PA 16802, USA 14Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands 15Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK 16N´ucleo de Astronom´a,Facultad de Ingenier´ay Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile 17Escuela de Ingenier´aIndustrial, Facultad de Ingenier´ay Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile Submitted to ApJL ABSTRACT PDS 70 is a unique system in which two protoplanets, PDS 70 b and c, have been discovered within the dust-depleted cavity of their disk, at 22 and 34 au respectively, by direct imaging at infrared ∼ wavelengths. Subsequent detection of the planets in the Hα line indicates that they are still accreting material through circumplanetary disks. In this Letter, we present new ALMA observations of the dust continuum emission at 855 µm at high angular resolution ( 20 mas, 2.3 au) that aim to resolve ∼ the circumplanetary disks and constrain their dust masses. Our observations confirm the presence of a compact source of emission co-located with PDS 70 c, spatially separated from the circumstellar disk and less extended than 1.2 au in radius, a value close to the expected truncation radius of the ∼ cicumplanetary disk at a third of the Hill radius. The emission around PDS 70 c has a peak intensity 1 of 86 16 µJy beam− which corresponds to a dust mass of 0.031 M or 0.007 M , assuming it ∼ ± ∼ ⊕ ∼ ⊕ is only constituted of 1 µm or 1 mm sized grains, respectively. We also detect extended, low surface brightness continuum emission within the cavity near PDS 70 b. We observe an optically thin inner disk within 18 au of the star with an emission that could result from small micron-sized grains transported from the outer disk through the orbits of b and c. In addition, we find that the outer disk resolves into a narrow and bright ring with a faint inner shoulder. Corresponding author: Myriam Benisty [email protected] 2 Benisty et al. Keywords: protoplanetary disks { planets and satellites: formation { stars: individual (PDS 70) 1. INTRODUCTION ited to the IR regime (1-5 µm) remain inconclusive, but Recent surveys revealed that almost ubiquitously, pro- suggest planet masses between 1 and a few MJup (e.g., toplanetary disks appear highly structured with rings M¨ulleret al. 2018; Mesa et al. 2019; Stolker et al. 2020) and gaps, spiral arms and asymmetries (e.g., Garufi as well as a clear contribution from dust grains in clouds et al. 2018; Andrews 2020). While other scenarios are and/or circumplanetary disks (CPDs) (Christiaens et al. discussed, these features are often interpreted as re- 2019; Stolker et al. 2020; Wang et al. 2020). sulting from the presence of planets embedded in disks CPDs play a fundamental role in planet formation, as (e.g., Dong et al. 2015; Bae et al. 2018; Lodato et al. they regulate the gas accretion onto the planet and de- 2019). Additional observational support for such a sce- termine the conditions for satellite formation. As gas nario can be found in the form of local perturbation enters the planet's sphere of influence, it falls at super- of the gas velocity field from Keplerian rotation (Pinte sonic velocities onto the surface of the CPD (Tanigawa et al. 2018; Teague et al. 2019; Casassus & P´erez 2019). et al. 2012; Szul´agyi& Mordasini 2017), possibly episod- The quest to detect protoplanets embedded in their host ically (Gressel et al. 2013), leading to shocks that can disk through direct imaging has been challenging with ionize hydrogen and be traced in the Hα line. From current detection limits on the order of a few Jupiter observations of the Hα line, PDS 70 b and PDS 70 c are masses (M ) at large radii (e.g., Hu´elamoet al. 2018; found to be accreting material from their host disk at Jup 8 a rate of 10− M per year (Wagner et al. 2018b; Asensio-Torres et al. 2021). A few protoplanet candi- ∼ Jup dates have been claimed in the infrared (IR) and in the Haffert et al. 2019; Thanathibodee et al. 2019; Aoyama & Ikoma 2019; Hashimoto et al. 2020). Using ALMA Hα line (e.g., Sallum et al. 2015; Reggiani et al. 2018) observations at 67 mas 50 mas resolution, Isella et al. but remain controversial (Mendigut´ıaet al. 2018). ∼ × The first robust detection of a protoplanet still embed- (2019) showed evidence for sub-millimeter continuum ded in its natal disk through direct imaging techniques emission co-located with PDS 70 c, interpreted as trac- was obtained in the young system PDS 70 (spectral type ing a dusty CPD, and for another compact continuum K7; M 0.8 M ; age 5.4 Myr old; M¨ulleret al. 2018) lo- emission source located at 74 mas offset in a South ∼ ∼ ∼ cated at 112.4 pc (Gaia Collaboration et al. 2020) in West direction from b. The emission around c how- ∼ the Upper Centaurus Lupus association (Pecaut & Ma- ever was not spatially separated from the outer ring. majek 2016). PDS 70 b was discovered with an orbital In this Letter, we present new ALMA observations with radius of 22 au, and imaged at multiple IR wavelengths 20 mas resolution that provide an independent detection ∼ (Keppler et al. 2018; M¨ulleret al. 2018) as well as in a of a compact source of emission colocated with PDS 70 c filter centered on the Hα line (Wagner et al. 2018a). and of low surface brightness emission within the cavity PDS 70 c was subsequently discovered in Hα imaging at close to PDS 70 b. The Letter is organized as follows: the outer edge of the cavity with an orbital radius of Section2 presents the observations and the procedure 34 au (Haffert et al. 2019). These two planets carve a to calibrate the data. Section3 presents our new im- ∼ large cavity in the disk, evidenced by a cavity in dust ages and analysis. Finally, we discuss our findings in (e.g., Hashimoto et al. 2012; Dong et al. 2012) and a gap Section4. in the 12CO gas emission along the orbit of PDS 70 b (Keppler et al. 2019) that indicates significant gas de- 2. OBSERVATIONS pletion. Observations and hydrodynamic simulations in- This paper presents new ALMA observations, here- dicate that the planets' orbital configuration is stable, after referred to as LB19 (for 'Long Baselines 2019'), close to a 2:1 mean motion resonance, with PDS 70 b in obtained in Band 7 (λ = 855 µm), under a Di- a slightly eccentric orbit (e 0.2; Bae et al. 2019; Toci ∼ rector's Discretionary Time (DDT) program with ID et al. 2020; Wang et al. 2021). The masses of the two 2018.A.00030.S. PDS 70 was observed during 4 execu- planets are still uncertain, although both planets are tion blocks (EB) with the C-8 configuration on 2019 likely lighter than 10 MJup to ensure dynamical stabil- July 27, 28, and 30, for a total on-source time of 43 ity (Wang et al. 2021) and a non-eccentric outer disk minutes per execution. An observing log including the (Bae et al. 2019). Spectro-photometric analyses, lim- precipitable water vapor (PWV) levels and calibrator names is given in Appendix A.1. The spectral set-up ∗ NASA Hubble Fellowship Program Sagan Fellow was tuned to optimize continuum detection, but includes the 12CO J=3-2 line at 345.8 GHz and the HCO+ J=4-3 A Circumplanetary Disk Around PDS70 c 3 Table 1. Summary of available ALMA Band 7 observations of PDS 70. MRS is the maximum recoverable scale. Label ID Date Baselines Frequency MRS References [m] [GHz] [arcsec] SB16 2015.1.00888.S 2016 Aug 14-18 15-1462 344-355 3.23 Long et al. 2018 IB17 2017.A.00006.S 2017 Dec 2-6 15-6855 346-357 1.05 Keppler et al.
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