Bibcode
Gutiérrez, Leonel; Giammanco, Corrado; Beckman, John E.
Referencia bibliográfica
Triggered Star Formation in a Turbulent ISM, Edited by B. G. Elmegreen and J. Palous. Proceedings of the International Astronomical Union 2, IAU Symposium #237, held 14-18 August, 2006 in Prague, Czech Republic. Cambridge: Cambridge University Press, 2007., pp.419-419
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2007
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Descripción
The Orion Nebula (NGC 1976, M42) contains the nearest massive star
forming region and is therefore ideal for studying the physical process
accompanying star formation. The high spatial resolution available with
HST imaging in emission lines and continuum permits highly detailed
study of such processes, as has been described notably by O'Dell (2001).
The unique opportunity to study proper motions has been used by O'Dell
and collaborators in a succession of articles, and here we extend their
work by constructing maps of proper motion velocities in several zones
of the central region, using the technique of cross-correlation, to
optimize the precision of the differential measurement of emission line
images separated in time by ~7 years. The second piece of work reported
is a search for time variability of the intensity between these images.
Spatial temperature inhomogeneities ("fluctuations") are a well-known
phenomenon in HII regions, affecting their use in interpretative work,
especially in the derivation of abundances, but their origin has never
been clearly resolved. Some possible mechanisms for producing them
entail quite rapid time variations of temperature on small scales and we
have looked for these using the same set of HST images as for the
proper motions, in OIII, NII and Halpha with the time separation cited
above. To discriminate against noise we used a digital filter which
eliminated high spatial frequencies, and by comparing the difference
images in different lines we could distinguish between variability due
to changes in density, or temperature, or to apparent changes due to
proper motions. We detected temperature variations of order 0.4% of the
mean temperature, on scales of 2x10 ^-2 pc. We also noted that these
were detectable in zones of minimum proper motion, while in zones with
high proper motion density fluctuations could be measured.