Browsing by Author "Boehler, Y."

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    The Complex Morphology of the Young Disk MWC 758: Spirals and Dust Clumps around a Large Cavity
    (IOP Publishing, 2018) Boehler, Y.; Ricci, L.; Weaver, E.; Isella, A.; Benisty, M.; Carpenter, J.; Grady, C.; Shen, Bo-Ting; Tang, Ya-Wen; Perez, L.
    We present Atacama Large Millimeter Array observations at an angular resolution of 0farcs1–0farcs2 of the disk surrounding the young Herbig Ae star MWC 758. The data consist of images of the dust continuum emission recorded at 0.88 millimeter, as well as images of the 13CO and C18O J = 3–2 emission lines. The dust continuum emission is characterized by a large cavity of roughly 40 au in radius which might contain a mildly inner warped disk. The outer disk features two bright emission clumps at radii of ~47 and 82 au that present azimuthal extensions and form a double-ring structure. The comparison with radiative transfer models indicates that these two maxima of emission correspond to local increases in the dust surface density of about a factor 2.5 and 6.5 for the south and north clumps, respectively. The optically thick 13CO peak emission, which traces the temperature, and the dust continuum emission, which probes the disk midplane, additionally reveal two spirals previously detected in near-IR at the disk surface. The spirals seen in the dust continuum emission present, however, a slight shift of a few au toward larger radii and one of the spirals crosses the south dust clump. Finally, we present different scenarios to explain the complex structure of the disk.
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    Vortex-like kinematic signal, spirals, and beam smearing effect in the HD 142527 disk
    (EDP Sciences, 2021) Boehler, Y.; Ménard, F.; Robert, C. M. T.; Isella, A.; Pinte, C.; Gonzalez, J.-F.; Plas, G. van der; Weaver, E.; Teague, R.; Garg, H.; Méheut, H.
    Vortices are one of the most promising mechanisms to locally concentrate millimeter dust grains and allow the formation of planetesimals through gravitational collapse. The outer disk around the binary system HD 142527 is known for its large horseshoe structure with azimuthal contrasts of ~3–5 in the gas surface density and of ~50 in the dust. Using 13CO and C18O J = 3–2 transition lines, we detect kinematic deviations to the Keplerian rotation, which are consistent with the presence of a large vortex around the dust crescent, as well as a few spirals in the outer regions of the disk. Comparisons with a vortex model suggest velocity deviations up to 350 m s−1 after deprojection compared to the background Keplerian rotation, as well as an extension of ±40 au radially and ~200° azimuthally, yielding an azimuthal-to-radial aspect ratio of ~5. Another alternative for explaining the vortex-like signal implies artificial velocity deviations generated by beam smearing in association with variations of the gas velocity due to gas pressure gradients at the inner and outer edges of the circumbinary disk. The two scenarios are currently difficult to differentiate and, for this purpose, would probably require the use of multiple lines at a higher spatial resolution. The beam smearing effect, due to the finite spatial resolution of the observations and gradients in the line emission, should be common in observations of protoplanetary disks and may lead to misinterpretations of the gas velocity, in particular around ring-like structures.