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Diffraction-limited Visible Light Images of Orion Trapezium Cluster With the Magellan Adaptive Secondary AO System (MagAO)

Authors :
Close, L. M.
Males, J. R.
Morzinski, K.
Kopon, D.
Follette, K.
Rodigas, T. J.
Hinz, P.
Wu, Y-L.
Puglisi, A.
Esposito, S.
Riccardi, A.
Pinna, E.
Xompero, M.
Briguglio, R.
Uomoto, A.
Hare, T.
Publication Year :
2013

Abstract

We utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high spatial resolution observations in "visible light" with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.5-0.7") we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r' (0.63 micron) images are slightly coarser at FWHM=23-29 mas (Strehl ~28%) with bright (R<9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~1 Myr) Orion Trapezium Theta 1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary Theta 1 Ori C1/C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ~0.6-5 mas accuracy. We now are sensitive to relative proper motions of just ~0.2 mas/yr (~0.4 km/s at 414 pc) - this is a ~2-10x improvement in orbital velocity accuracy compared to previous efforts. For the first time, we see clear motion of the barycenter of Theta 1 Ori B2/B3 about Theta 1 Ori B1. All five members of the Theta 1 Ori B system appear likely a gravitationally bound "mini-cluster", but we find that not all the orbits can be both circular and co-planar. The lowest mass member of the Theta 1 Ori B system (B4; mass ~0.2 Msun) has a very clearly detected motion (at 4.1+/-1.3 km/s; correlation=99.9%) w.r.t B1 and will likely be ejected in the future. This "ejection" process of the lowest mass member of a "mini-cluster" could play a major role in the formation of low mass stars and brown dwarfs.(slightly abridged abstract)<br />Comment: 35 pages, 17 figures, to appear in the Sept. 10, 2013 issue of ApJ

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.1308.4155
Document Type :
Working Paper
Full Text :
https://doi.org/10.1088/0004-637X/774/2/94