The magnetic field in the star-forming region Cepheus A. from H_2O maser polarization observations

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Characterization of Ring Substructures in the Protoplanetary Disk of HD 169142 from Multiwavelength Atacama Large Millimeter/submillimeter Array Observations

We present a detailed multiwavelength characterization of the multi-ring disk of HD 169142. We report new Atacama Large Millimeter/submillimeter Array (ALMA) observations at 3 mm and analyze them together with archival 0.89 and 1.3 mm data. Our observations resolve three out of the four rings in the disk previously seen in high-resolution ALMA data. A simple parametric model is used to estimate the radial profile of the dust optical depth, temperature, density, and particle size distribution. We find that the multiple ring features of the disk are produced by annular accumulations of large particles, probably associated with gas pressure bumps. Our model indicates that the maximum dust grain size in the rings is ∼1 cm, with slightly flatter power-law size distributions than the interstellar medium-like size distribution (p ∼ 3.5) found in the gaps. In particular, the inner ring (∼26 au) is associated with a strong and narrow buildup of dust particles that could harbor the necessary conditions to trigger the streaming instability. According to our analysis, the snowlines of the most important volatiles do not coincide with the observed substructures. We explore different ring formation mechanisms and find that planet-disk interactions are the most likely scenario to explain the main features of HD 169142. Overall, our multiwavelength analysis provides some of the first unambiguous evidence of the presence of radial dust traps in the rings of HD 169142. A similar analysis in a larger sample of disks could provide key insights on the impact that disk substructures have on the dust evolution and planet formation processes.© 2019. The American Astronomical Society. All rights reserved..E.M., and C.C.E. acknowledge support from the National Science Foundation under CAREER grant No. AST-1455042 and the Sloan Foundation. M.O., G.A., J.M.T., and J.F.G. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the AYA2017-84390-C2-1-R grant (co-funded by FEDER). M.O., G. A., and J.F.G. acknowledge support from the >Center of Excellence Severo Ochoa> award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). M. F. and G.H.M.B. acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no 757957).Peer Reviewe

VLA observations of ammonia and continuum in regions with high-velocity gaseous outflows. II

We present VLA observations of the (1, 1) inversion transition of ammonia toward four regions with highvelocity gaseous outflow: HH 26-IR, GGD 12-15, Serpens, and V645 Cygni. We detected small-scale structure (~ 10>) in all sources. In HH 26-IR and GGD 12-15 we find double-maximum structures that could be related to the collimation processes of the outflow. The condensations observed in Serpens and V645 Cygni appear to be the cores of the more extended structures mapped with a single dish. Subject headings: interstellar: molecules — nebulae: H n regionsJ. M. T. and L. V. are partially supported by SEUI (Spain) grant PB87-0371 and by Junta de Andalucía (Spain)Peer Reviewe

V645Cygni: A decelerating molecular outflow?

V 645 Cygni (AFGL 2789) is a young stellar object associated with a bipolar molecular outflow with a modest degree of collimation. In this paper we present IR AM 30-m observations of the CO(J=2→1), CO(J=1→0) and C0(J= 1→0) rotational transition lines toward this region. At relatively low velocities the molecular outflow presents a bipolarity in the north-south direction, with the red and blueshifted CO lobes separated by ∼ 20Prime;. This angular separation decreases as the velocity increases. At higher velocities the outflow appears isotropic. The physical parameters obtained for the V645 Cyg molecular outflow (i.e., mass, momentum rate and mechanical luminosity) are much lower than the parameters derived for other outflows with exciting sources of similar luminosities (L∗≃10 L). In particular, this result makes it possible that radiation pressure may be responsible for generating the stellar wind associated with V645 Cyg. All these results lead us to suggest that the outflowing molecular gas could be decelerating as it moves away from the central V645 Cyg position. The integrated CO emission presents an elongated structure with a velocity gradient of ∼0.7 km s pc in the east-west direction. The mass derived is sufficient to bind these motions.Peer Reviewe

Heteroepitaxial growth of anatase (0 0 1) films on SrTiO3 (0 0 1) by PLD and MBE

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Characterizing the radio continuum nature of sources in the massive star-forming region W75N (B)

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