LARGE-SCALE ASYMMETRIES IN THE TRANSITIONAL DISKS OF SAO 206462 AND SR 21

By L. P'erez, Andrea Isella, J. Carpenter, C. Chandler. 2014

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We present Atacama Large Millimeter/submillimeter Array (ALMA) observations in the dust continuum (690 GHz, 0.45 mm) and 12CO J = 6–5 spectral line emission of the transitional disks surrounding the stars SAO 206462 and SR 21. These ALMA observations resolve the dust-depleted disk cavities and extended gaseous disks, revealing large-scale asymmetries in the dust emission of both disks. We modeled these disk structures with a ring and an azimuthal Gaussian, where the azimuthal Gaussian is motivated by the steady-state vortex solution from Lyra & Lin. Compared to recent observations of HD 142527, Oph IRS 48, and LkHα 330, these are low-contrast (≲ 2) asymmetries. Nevertheless, a ring alone is not a good fit, and the addition of a vortex prescription describes these data much better. The asymmetric component encompasses 15% and 28% of the total disk emission in SAO 206462 and SR 21, respectively, which corresponds to a lower limit of 2 MJup of material within the asymmetry for both disks. Although the contrast in the dust asymmetry is low, we find that the turbulent velocity inside it must be large (∼20% of the sound speed) in order to drive these azimuthally wide and radially narrow vortex-like structures. We obtain residuals from the ring and vortex fitting that are still significant, tracing non-axisymmetric emission in both disks. We compared these submillimeter observations with recently published H-band scattered light observations. For SR 21 the scattered light emission is distributed quite differently from the submillimeter continuum emission, while for SAO 206462 the submillimeter residuals are suggestive of spiral-like structure similar to the near-IR emission.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/bdd7475b4c107f2cc42a953067761ee0c927f5c2

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Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA (2015, methodology): “ALMA CO pure rota- ⋆ Jansky Fellow of the National Radio Astronomy Observatory tional line observations reveal directly the presence of gas inside the dust cavity (van der Marel et al. 2013; Bruderer et al. 2014; Pérez et al. 2014; Casassus et al. 2013; Zhang et al. 2014).”
Resolved gas cavities in transitional disks inferred from CO isotopologs with ALMA (2015, background): “Spatially resolved ALMA observations of 12CO emission confirm the presence of gas inside the dust cavity for several other disks (van der Marel et al. 2013; Casassus et al. 2013; Pérez et al. 2014; Zhang et al. 2014; Canovas et al. 2015).”
The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, background): “…particle traps exhibit complex substructures, including azimuthal asymmetries (Casassus et al. 2013; van der Marel et al. 2013; Isella et al. 2013; Pérez et al. 2014), additional rings (Fedele et al. 2017; van der Plas et al. 2017), warped geometries (and/or radial inflows; Rosenfeld et al.…”
MILLIMETER-WAVE POLARIZATION OF PROTOPLANETARY DISKS DUE TO DUST SCATTERING (2015, background): “Since broad range of azimuthal contrast of dust continuum emission has been reported so far (1.5 for SAO206462; Pérez et al. 2014, 24 for HD 142527; Fukagawa et al. 2013, 130 for IRS 48; van der Marel et al. 2013), we consider two cases: model A for low azimuthal contrast and model B for high…”
Multiwavelength analysis for interferometric (sub-)mm observations of protoplanetary disks - Radial constraints on the dust properties and the disk structure (2015, background): “…with ALMA early science observations in several disks and interpreted as dust traps, with the large grains being more concentrated than the small grains and the molecular gas (van der Marel et al. 2013, 2015; Fukagawa et al. 2013; Pérez et al. 2014; Casassus et al. 2015; Marino et al. 2015).”
Observational Signatures of Planets in Protoplanetary Disks I: Gaps Opened by Single and Multiple Young Planets in Disks (2014, background): “Gap Size Dependence on Wavelengths One class of transitional disks have a clear cavity at mm, but no gap/cavity down to the inner working angle in NIR imaging (Dong et al. 2012b, e.g. SR 21, Pérez et al. 2014; Follette et al. 2013).”
ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii (2018, background): “…linked to dust trapping in vortices (e.g., van der Marel et al. 2013; Casassus et al. 2015; Kraus et al. 2017), whereas shallower asymmetries with contrasts of < 2–3 (e.g., Pérez et al. 2014; Pinilla et al. 2015) have been explained by other mechanisms (e.g., eccentricity; Ataiee et al. 2013).”
Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 (2018, background): “…al. 2014b; Perez et al. 2015; Pohl et al. 2017b; Hendler et al. 2018), azimuthal asymmetries (e.g. Casassus et al. 2013; van der Marel et al. 2013; Pérez et al. 2014), spirals (e.g. Muto et al. 2012; Grady et al. 2013; Tang et al. 2017), and multiple rings (e.g. de Boer et al. 2016; Ginski et al.…”
OBSERVATIONAL SIGNATURES OF PLANETS IN PROTOPLANETARY DISKS: SPIRAL ARMS OBSERVED IN SCATTERED LIGHT IMAGING CAN BE INDUCED BY PLANETS (2015, background): “At this moment resolved mm observations of these objects suffer from insufficient spatial resolution, and could not pinpoint the mm counterparts of these arms (Chapillon et al. 2008; Isella et al. 2010, 2013; Andrews et al. 2011; Pérez et al. 2014; Marino et al. 2015).”
Multiple Disk Gaps and Rings Generated by a Single Super-Earth (2017, background): “The leading explanation for lopsided disks observed by ALMA (e.g., van der Marel et al. 2013; Casassus et al. 2013; Pérez et al. 2014)—vortices formed at planet-opened gap edges—requires α .”
Shadows and spirals in the protoplanetary disk HD 100453 (2016, background): “On the other hand, other sub-millimeter images showed, azimuthally asymmetric brightness enhancements in continuum (Casassus et al. 2012; van der Marel et al. 2015; Pérez et al. 2014; Pinilla et al. 2015c) and in very few objects, spiral arms (Christiaens et al. 2014; Pérez et al. 2016).”
ALMA SURVEY OF LUPUS PROTOPLANETARY DISKS. I. DUST AND GAS MASSES (2016, background): “…and their dust and gas distributions may be in some cases signposts of embedded planets clearing gaps in the disk (e.g., Pinilla et al. 2012; Pérez et al. 2014; van der Marel et al. 2015, 2016a; Canovas et al. 2015) Our ALMA continuum images show several Lupus disks with signatures of…”
On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening (2017, background): “As for the gaseous counterparts to these stellar disks, AGN disks may be messy, sharing the large-scale structures evident in high resolution observations of protoplanetary disks (e.g. van der Marel et al. 2013; Pérez et al. 2014; Casassus et al. 2013; Flock et al. 2015).”
Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations (2014, background): “…submillimeter wavelengths, for instance, in the systems Oph IRS 48 (van der Marel et al. 2013), LkHα 330 (Isella et al. 2013), SAO 206462 and SR 21 (Pérez et al. 2014), or in HD 142527 (Casassus et al. 2013; Fukagawa et al. 2013), in which one has recently found a low-mass stellar companion…”
Dust Evolution and the Formation of Planetesimals (2016, background): “Similar asymmetries in the ring-like dust emission from transition disks have been detected in Casassus et al. (2013) and Pérez et al. (2014).”