10636( 1) - 04/05/05 12:09 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10636 Version: 1 Check-in Date: 05-Apr-2005 16:09:22 1.Proposal Title: Physical Processes in Orion's Veil: A High Resolution UV Absorption Study of the Line of Sight Towards the Trapezium ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance AR 14 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Mr. Nicholas P. Abel University of Kentucky CoI: Dr. Gary J. Ferland University of Kentucky N CoI: Dr. C. Robert O'Dell Vanderbilt University N CoI: Dr. Thomas H. Troland University of Kentucky N ------------------------------------------------------------------------------------ 6. Abstract Star Formation is a complex interplay among magnetic, thermal, turbulent and gravitational energies. Magnetic energies are crucial to the evolution of molecular clouds, when comparable to other energies. Magnetic field strength measurements are, however, sparse. Detailed field strength maps exist in only one region of the ISM, the veil of neutral material in front of the Orion Nebula. From the Zeeman Effect seen in 21cm H I absorption, we have maps of the field strength in two velocity components. The veil is therefore a unique laboratory to study magnetic effects in star forming regions. Abel et al. (2004) combined archival IUE absorption data with modeling to estimate the veil's density, temperature, and level of ionization. We found that magnetic energies far exceeded other energies in at least one of the components. This is unique, as data from other regions suggest energy equipartition. Unfortunately, IUE data lacked the resolution to separate both H I components, meaning our models are average conditions over both components. We propose an archival, high-resolution UV study to determine conditions in both velocity components. Previous studies obtained spectra in the 2124-2496 & 1170-1372 Angstrom range, for study of C and O abundances in translucent clouds. We will analyze this data for other lines, which we predict in our calculations and are observed in previous IUE studies. Multiple ionization stages for S, Si, C, and Fe should be observed, along with excited state O I absorption, a good density diagnostic. Archival data combined with modeling will determine the density, temperature, and level of ionization in each velocity component. We will compare magnetic and thermal energies in each component, along with determining the distance of each component from the Trapezium. This will lead to a better understanding of the role of magnetic fields in star forming regions. This is analogous to approved proposal 10124, which was granted time on STIS to obtain high resolution UV data for the same line of sight (which, due to the failure of STIS, could not be executed). ------------------------------------------------------------------------------------ 10636( 1) - 04/05/05 12:09 - [ 2] Summary Form for Proposal 10636 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category AR ------------------------------------------------------------------------------------------------------------------------------------