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Magnetic fields are expected to play a crucial role in the dynamics of the ISM, but are notoriously difficult, and usually telescope-costly, to measure in quantitative ways. The observationally easiest way of tracing the magnetic field, at moderate extinction, is through the used of optical/NIR polarimery of background stars (and the corresponding use of polarized FIR emission for cloud cores). This polarization is generally agreed to be caused by dichroic extinction (emission) due to asymmetric dust grains aligned by the magnetic field. Using the statistical Chandrasekhar-Fermi (CF) method, such data also allows the field strength to be estimated. The interpretation of the polarimetry is, however, hampered by the lack of a detailed understanding of the grain alignment physics. Major theoretical advances over the last couple of decades have ? until recently ? not been matched by similar observational progress. I will discuss new multi-wavelength optical/NIR polarimetry, supported by optical, NIR and FIR photometry, which provides observational support for radiation driven grain alignment, but also yields some surprises. I will show that cloud geometry and the presence of hot stars - nearby to, and embedded in, the clouds ? can significantly affect the results and have to be taken into account in the data analysis. In addition to providing empirical evidence for the dominant alignment mechanism, this kind of data will allow us to constrain and study secondary alignment and disalignment mechanisms.
The topics of the CARMA seminar include the solar system, star formation, the interstellar medium, galactic structure and galaxies. All are welcome to attend. Seminars will be limited to 1 hour including questions.
LMA Phone Number: (301) 405-1502Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.
Parking for visitors is available in the Cashier-Attended Parking Lot at the intersection of Paint Branch & Technology Drive. It is a 5-10 minute walk from the parking lot to the Computer & Space Sciences building.
There are a limited number of parking meters in Lot DD; there are no parking meters in Parking Garage 2. Parking at non-metered spaces in Lot DD and PG2 is free after 4 pm and on weekends.
More information is available from the Department of Campus Parking.
Department of Astronomy, University of Maryland College Park, MD 20742-2421 Phone: (301) 405-3001 FAX: (301) 314-9067 Comments and questions may be directed to webmaster@astro.umd.edu
This page was automatically generated on:
13-Mar-2008.
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