The curious morphology and orientation of Orion proplyd HST-10
  HST-10 is one of the largest proplyds in the Orion Nebula and is located
approximately 1' SE of the Trapezium. Unlike other proplyds in Orion, however,
the long-axis of HST-10 does not align with theta 1 C Ori, but is instead
aligned with the rotational axis of the HST-10 disk. This cannot be easily
explained using current photo-evaporation models. In this letter, we present
high spatial resolution near-infrared images of the Orion proplyd HST-10 using
Keck/NIRC2 with the Laser Guide Star Adaptive Optics system, along with
multi-epoch analysis of HH objects near HST-10 using Hubble Space Telescope
WFPC2 and ACS cameras. Our narrow-band near-IR images resolve the proplyd
ionization front (IF) and circumstellar disk down to 23 AU at the distance to
Orion in Br gamma, He I, H_2, and PAH emission. Br gamma and He I emission
primarily trace the IF (with the disk showing prominently in silhouette), while
the H_2 and PAH emission trace the surface of the disk itself. PAH emission
also traces small dust grains within the proplyd envelope which is asymmetric
and does not coincide with the IF. The curious morphology of the PAH emission
may be due to UV-heating by both theta 1C Ori and theta 2A Ori. Multi-epoch HST
images of the HST-10 field show proper motion of 3 knots associated with HH
517, clearly indicating that HST-10 has a jet. We postulate that the
orientation of HST-10 is determined by the combined ram-pressure of this jet
and the FUV-powered photo-ablation flow from the disk surface.
