CTIO Scientific Staff
Star Formation, Herbig-Haro Objects, Supernovae and Novae
Heathcote's recent research efforts have concentrated on the study of Herbig-Haro jets using high spatial resolution images obtained with the Hubble Space Telescope. It is now known that stars in the process of formation blow extremely powerful, often highly collimated winds. The collision of these highly supersonic outflows with gas surrounding the nascent star excites luminous shock waves, which we observe as a Herbig-Haro jet. These jets provide key information about the mechanisms at play in forming a star. In particular it is possible to measure how much mass the star is losing now and how the rate of mass loss has varied over the last few thousand years. Such jets are also valuable astrophysical laboratories for the study of shock physics and chemistry. In two recently completed papers Heathcote and collaborators, B. Reipurth (ESO), R. Schwartz (U. Missouri), J. Bally (U. Colorado), J. Morse (U.Colorado), P. Hartigan (Rice University), and J. Stone (U. Maryland) present HST images of two of the finest examples of such jets, HH 46/47 (AJ 112, 1141) and HH 111 (AJ in press). These images provide the first clear evidence that shocks within these jets are excited by fluctuations in the velocity and direction of the outflow from the source. At the very high spatial resolution obtained with HST it is possible to study for the first time the structure of the zone behind these shocks. The data also provide new insights into the way in which jets sweep up material in their surroundings, helping to clear away the debris left behind after formation of the star. In a separate project, carried out in collaboration with B. Reipurth (ESO) and A. Raga (UNAM) , Heathcote has combined HST images, with ground based high resolution spectroscopy and proper motion measurements to study the structure and kinematics of the HH 80/81 complex. Whereas most HH flows (including HH 46/47 and HH 111) are driven by low luminosity stars with masses similar to that of the Sun, the source of the HH 80/81 outflow is a much more luminous, B0 type star. This system thus provides a rare opportunity to study how outflow properties depend on the power of the driving source.
During the next year Heathcote will re-observe four HH jets already imaged with HST. The velocities of such jets are so high that motion is detectable over periods of only one or two years. Thus these second epoch images will supply crucial information on how the various shock waves move and how they change with time. Heathcote in collaboration with B. Reipurth (ESO) , M. McCaughrean (MPIfR) and H. Zinnecker (Potsdam) will also obtain IR images of two HH jets using both the NICMOS imager on HST and the COB imager plus tip-tilt secondary on the Blanco 4-m telescope. While the optical emission from an HH jet traces the strongest shocks, molecular hydrogen emission in the IR probes the weaker shocks at the periphery of the jet. At IR wavelengths it is also possible to study the sections of the jet closer to the driving source, which is hidden from view in the optical by overlying extinction.
Heathcote is responsible for scientific oversight of CTIO's computer system and network and of the CTIO computer programming group. He also supervises the data reduction assistants on Cerro Tololo. During the past two years, Heathcote has been heavily involved in the software side of CTIO's Arcon CCD controllers. He is consequently closely involved with the development of the NOAO CCD mosaic imager, based on these controllers, which will be commissioned during 1996. Heathcote is also project scientist and manager for a multi-year project to upgrade the drives and control system for the Blanco 4-m telescope. Heathcote is a member of the Advisory Committee on Technical Resources at CTIO.
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