SPIRAL STRUCTURE AND DIFFERENTIAL DUST SIZE DISTRIBUTION IN THE LkHα 330 DISK

Abstract

Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 μm) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkHα 330. As a result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (β) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side ( ) but are much smaller in the west side , indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y–K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.

Meso-scale Instability Triggered by Dust Feedback in Dusty Rings: Origin and Observational Implications

“…Over the past few years, observations obtained with the Atacama Large Millimeter Array (ALMA) have revealed small scale structures in the distribution of (sub)millimeter dust grains around many circumstellar disks surrounding nearby young stars. The majority of the millimeter bright disks observed so far feature multiple rings and gaps characterized by radii spanning from a few to a few hundreds of astronomical units (au) (Brogan et al 2015;Andrews et al 2016;Isella et al 2016;Andrews et al 2018a;Huang et al 2018a;Fedele et al 2018;Pérez et al 2018a;Andrews et al 2018b;Huang et al 2018b;Guzmán et al 2018;Dullemond et al 2018;Isella et al 2018), while a smaller fraction of objects show prominent dust crescents (Fujiwara et al 2006;Isella et al 2010Isella et al , 2013van der Marel et al 2013;Pérez et al 2014;van der Marel et al 2016;Boehler et al 2017;Benisty et al 2018;Cazzoletti et al 2018;Pérez et al 2018b;Boehler et al 2018) and spiral arms (Grady et al 2012;Benisty et al 2015;Akiyama et al 2016;Boehler et al 2018;Dong et al 2018b;Huang et al 2018c;Uyama et al 2018).…”

Spirals inside the millimeter cavity of transition disk SR 21

“…We mark the location of the outer planet with a circle in the model image and the location of the kinked spiral in the data in the top panel.are observed these are the dominating structures in the disk, see e.g. the HD 135344 B system(Muto et al 2012;Garufi et al 2013;Stolker et al 2016), the MWC 758 system(Grady et al 2013;Benisty et al 2015) or the LkHa 330 system(Akiyama et al 2016;Uyama et al 2018). In all of these cases the scattered light spirals are launched from an inner ring and are the outermost structures visible.…”

Modelling of deep gaps created by giant planets in protoplanetary disks

“…High-resolution images have revealed the presence of complex morphological structures in disks; these structures include spirals (e.g., Muto et al 2012;Grady et al 2013;Christiaens et al 2014;Benisty et al 2015;Currie et al 2015;Akiyama et al 2016) and gaps (e.g., Osorio et al 2014; ALMA Partnership et al 2015;Momose et al 2015;Akiyama et al 2015;Nomura et al 2016;Yen et al 2016;Tsukagoshi et al 2016). Direct images are now finding possible signatures of planets being formed in disks (e.g., Sallum et al 2015).…”