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Evidence of Photoevaporation and Spatial Variation of Grain Sizes in the Orion 114-426 Protoplanetary Disk

Miotello, Anna and Robberto, Massimo and Potenza, Marco A. C. and Ricci, L. (2012) Evidence of Photoevaporation and Spatial Variation of Grain Sizes in the Orion 114-426 Protoplanetary Disk. Astrophysical Journal, 757 (1). Art. No. 78. ISSN 0004-637X. doi:10.1088/0004-637X/757/1/78.

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Deep Hubble Space Telescope broadband images taken with Advanced Camera for Surveys (ACS) and WFPC2 of the giant (~1000 AU diameter) dark silhouette proplyd 114-426 in the Orion Nebula show that this system is tilted, asymmetric, warped, and photoevaporated. The exquisite angular resolution of ACS allows us to map the distribution of dust grains at the northern translucent edge of the disk, dominated by the photoevaporative flow. Using the Mie theory for standard circumstellar disk grains, we find evidence for a spatial gradient in grain size. The typical dust radius ≃ 0.2-0.7 μm (less than what was reported by previous studies) becomes smaller as the distance from the disk center increases, consistent with the expectations for the dynamic of dust entrained in a gaseous photoevaporative wind. Our analysis of the disk morphology and location within the nebula indicates that this system is photoevaporated by the diffuse radiation field of the Orion Nebula, while being shielded from the radiation coming directly from the central Trapezium stars. We estimate the mass-loss rate from the disk surface and the timescale for total disk dissipation, which turns out to be of the order of 104 yr. Such a short time, of the order of 1/100 of the cluster age, indicates that this system is seen on the verge of destruction. This is compatible with the exceptional nature of the disk, namely its combination of huge size and low mass. Finally, we briefly discuss the viability of possible mechanisms that may lead to the peculiar morphology of this system: external UV flux, binary star, and past close encounter.

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Additional Information:© 2012 American Astronomical Society. Received 2012 April 2; accepted 2012 July 26; published 2012 September 5. The authors thank S. Lubow, I. Pascucci, J. Pringle, and K. Stapelfeld for helpful discussions on this fascinating source, and the referee W. Henney for prompt and useful feedback. Zolt Levay provided support with image production. Support for GO program 10246 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
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Space Telescope Science Institute (STScI)UNSPECIFIED
NASANAS 5-26555
Subject Keywords:circumstellar matter; dust, extinction; protoplanetary disks; stars: formation; stars: pre-main sequence
Issue or Number:1
Record Number:CaltechAUTHORS:20121101-103939682
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Official Citation:Evidence of Photoevaporation and Spatial Variation of Grain Sizes in the Orion 114-426 Protoplanetary Disk Anna Miotello et al. 2012 ApJ 757 78
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35237
Deposited On:01 Nov 2012 20:38
Last Modified:09 Nov 2021 23:13

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