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We present high angular resolution (1.2″), narrow band (Δλ/λ = 0.1) images of the nucleus of NGC253 at three wavelengths in the mid-IR (8.5, 10.0, and 12.5µm). We find that most of the mid-IR flux in the nucleus of NGC253 derives from a very small region ≤ 120 pc in diameter. Within this small region there are three spatially and spectrally distinct IR components: two bright compact sources, and a surrounding envelope of low level, diffuse emission. The mid-IR and 6cm radio are loosely correlated in position but not in brightness. The implication is that the mid-IR — radio correlation may begin to break down on small spatial scales relevant to individual star forming regions and large individual sources. These variations in the mid-IR spectra and in the radio-IR correlation imply that the nuclear emission is excited by more than one mechanism and source type.

We present 9.7 and 11.8 µm narrow band (Δλ/λ = 10%) images of three carbon (C-) rich proto-planetary nebulae with an unusual 21 µm feature: IRAS 07134+ 1005, IRAS 22272+5435, and IRAS 04296+3429. The images were taken at UKIRT using the Berkeley/IGPP/LEA mid-IR camera. All three objects have a bipolar shape adding to the existing evidence that C-rich PPNe are by nature bipolar. Furthermore, we find the same bipolar morphology in a previous study of the C-rich, young planetary nebula, IRAS 21282+5050. We believe these four objects form an evolutionary sequence which links the C-rich asymptotic giant branch (AGB) stars with the C-rich planetary nebulae (PNe). From this evolutionary sequence, we conclude that bipolarity in C-rich PNe begins on the AGB and that the dynamical ages of these PPNe are in fair agreement with theoretical ages for a 0.6 M⊙ hydrogen burning core star.

We resolved dust shells at 10.5 and 12.5 µm around the post asymptotic giant branch stars HD 161796 and AFGL 2343, two oxygen-rich proto-planetary nebulae with very cold IRAS colors. The shell of AFGL 2343 appears as a circular ring with 4″ – 5″ diameter, while HD 161796 appears bipolar with 2″ diameter. Inner shell radii indicate that both stars left the asymptotic giant branch about 200 years ago.

A simple calculation of the expected spectral signatures of model protostellar accretion flows suggests how the rotation curve of the accretion disk may be deduced from radio frequency molecular line observations. We compare synthetic observations with actual data to derive rotation curves, braking torques, and minimum magnetic field energies required to effect the braking

We present a 3-D hydrodynamical and radiative transfer simulation which suggests that the circular “necklace” of massive star formation in W49A may result from fragmentation via a ring instability during the collapse of a rotating cooling molecular cloud.