New silhouette disks with reflection nebulae and outflows in the Orion nebula and M43.
SMITH N., BALLY J., LICHT D. and WALAWENDER J.
Abstract (from CDS):
We report the detection of several new circumstellar disks seen in silhouette against background nebular light in the outskirts of the Orion Nebula and the neighboring H II region M43. These were detected as part of our Hα survey of Orion with the Advanced Camera for Surveys on board the Hubble Space Telescope. Several of the disks show bipolar reflection nebulae, microjets, or pronounced temporal variability of their central stars. The relatively large fraction of bipolar reflection nebulae and microjets in our sample may be a selection effect caused by the faint nebular background far from the Trapezium. Two disks in our sample are large and particularly noteworthy: A nearly edge-on disk, d216-0939, is located several arcminutes northwest of M43 and resembles the famous HH 30 disk/jet system in Taurus. It drives the 0.15 pc long bipolar outflow HH 667 and exhibits a remarkable asymmetric reflection nebula caused by the tilt of the flared disk. With a diameter of ∼2".6 (1200 AU), d216-0939 is as large as the giant edge-on silhouette disk d114-426 in the core of the Orion Nebula. The large disk d253-1536 is located in a binary system embedded within an externally ionized giant proplyd in M43. The disk exhibits distortions that we attribute to tidal interactions with the companion star. The bipolar jet HH 668 emerges from the proplyd ionization front in a direction orthogonal to the disk and can be traced to the young star embedded within it. A bow shock lies 54" south of this binary system along the outflow axis. Proper motions over a 1.4 yr baseline confirm that these emission knots are indeed moving away from d253-1536 with speeds as high as ∼330 km/s in the HH 668 microjet and slower motion farther from the star.