Ronald G. Probst
CTIO Scientific Staff
Areas of Interest
Star Forming Regions, Low Mass Stars, Infrared Imaging Instrumentation
Recent Research Results
Infrared astronomy has been largely technology driven. Over the past
decade, NOAO's deployment of sensitive, large format infrared detector
arrays in robust and flexible imaging systems has brought an immense
increase in scientific capability to the astronomical community. A part
of Probst's research has been to apply this capability to the study of
photodissociation regions: the boundary layers between hot, thin,
ionized gas and cold, dense, molecular material. These layers are
associated with stellar birth, as hot young stars carve holes in their
natal dust clouds; and stellar death, when radiation from newly exposed
inner portions of a star interacts with material ejected earlier from
its outer layers. One of the best techniques for tracing these regions
is imaging in the 2.12 mm line of molecular hydrogen. The morphology
itself offers insight into the processes at work, and quantitative
measurement of radiation at this wavelength is a guide to the energy
exchange. While on sabbatical at CTIO, Probst has assembled a special
purpose small telescope and coupled it to a facility IR camera equipped
with custom filters. This permits imaging of H2 emission over an area
the size of the full Moon in a single picture, a unique and powerful
capability for mapping extended faint structure. Probst has applied
this technique to the molecular cloud in which the Orion Nebula is
imbedded in order to trace the complex H2 morphology of this nearby
region of massive star formation. He has also extended this work to H2
imaging of star forming regions in the Large Magellanic Cloud with the
CTIO 1.5-m telescope. Use of a large telescope on a more distant object
enables comparisons at the same linear scales. A surprising result is
the complex and extensive H2 morphology of the 30 Dor region, a more
energetic region of star formation than Orion which serves as a
stepping stone to the starburst phenomenon seen in more distant
galaxies.
Future Research Plans
Probst plans to follow up this work with additional infrared imaging
and spectroscopy of star forming regions in the Large Magellanic Cloud.
Higher spatial resolution provided by larger telescopes, together with
IR adaptive optics soon to be implemented at CTIO, will improve the
morphological understanding of the 30 Dor H2 complex. Imaging in other
infrared lines, made possible in part by the deployment of new
detectors, will enable determination of dust extinction. This helps to
disentangle the actual three-dimensional structure of this star
forming region. H2 emission can be induced by the impact of a shock
front on neutral material, or as fluorescence caused by radiation of
the appropriate wavelength. Infrared spectroscopy will allow
discrimination between these much different physical mechanisms by
measurement of H2 line strengths. It may also be possible to infer the
neutral hydrogen content of the LMC directly, a fundamental and poorly
understood parameter for study of the star formation process in an
environment much different from our own surroundings in the Galaxy.
Together with Monica Rubio (U. of Chile) as principal investigator,
Probst will use the SEST telescope at ESO for high resolution
millimeter wave maps to trace the spatial and density structure of cold
molecular gas around 30 Dor.
Service
Probst's staff position as a Support Scientist requires him to spend
the bulk of his time in service activities. As a member of the KPNO
Infrared Group, he has been centrally involved in the development and
deployment of infrared imaging systems over the past ten years. This
involves close interaction with engineering staff during design and
construction, in order to deliver a scientifically capable, technically
maintainable, astronomer friendly instrument; and with scientific users
at the telescope, so that they may get the most out of an instrument's
capabilities. His most recent, multiyear endeavor has been as Project
Scientist for the Cryogenic Optical Bench (COB), an advanced imager
with multiple spatial and spectral filtering capabilities. After
bringing this instrument from conceptual design through construction to
deployment at the focal plane as a facility instrument, Probst was
Project Scientist for its upgrade to high spatial resolution capability
in the Diffraction Limited IR Imager (DLIRIM) project. As part of a
rebalancing of instrumental resources between CTIO and KPNO, COB will
be upgraded to a larger detector and redeployed permanently at CTIO,
where it will serve as the science sensor in a tip-tilt adaptive optics
system on the 4-m telescope. Probst will accompany the instrument to
Chile, transferring to the CTIO staff for a three year period. He will
be responsible for bringing this combination on-line as a user
facility. As a part of his continuing support of facility IR
instruments, Probst provides assistance to potential observers in the
preparation of technically competent proposals and does feasibility
review on all IR imaging proposals received in our biannual cycle. In
addition to his service in the Infrared Group, Probst recognized the
benefits to be gained from a systematic, mountain-wide program of
collimation and related optical work on facility telescopes. He
therefore created the position of Optics Scientist and served in this
role for two years, coordinating engineering and mountain technical
staff in the improvement of delivered image quality at all KPNO focal
planes. This initial effort led to the creation of a new scientific
staff position with enlarged responsibilities, subsequently filled by
C. Claver. Finally, while on sabbatical at CTIO, Probst has been
working with operations staff to prepare the infrastructure necessary
for receipt, maintenance, and operation of COB and other large infrared
instruments which will be deployed there.
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Posted: 06Dec1996