Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/vscience/schedule/tpfiles/CrutchertagA1901tp.ps Дата изменения: Tue May 25 19:57:33 2004 Дата индексирования: Sat Dec 22 23:13:14 2007 Кодировка: Поисковые слова: molecular cloud

Proposal Identification No.: A1901 Date Received: 2004­Jan­29 18:49:22
Technical Page
Proposal Type: Regular
General Category: Astronomy
Sub­Category: Spectroscopy
Observation Category: Galactic
Total Time Requested: 20 Hours
Proposal Title: OH Zeeman Test of Faraday Rotation in Dark Cloud Envelopes
ABSTRACT:
The magnetic support model for star formation has ambipolar di#usion increasing the mass­to­magnetic flux ratio
in cores until they become magnetically supercritical and collapse. The model absolutely requires that envelopes be
subcritical. Previous OH Zeeman measurements were pointed toward cores and do not address whether envelopes
are subcritical. Recently Wollenben and Reich interpreted low synchrotron polarization found at the boundaries of
nearby molecular clouds as being due to Faraday screens produced by Faraday rotation in the envelopes of these
clouds. They inferred line­of­sight field strengths of 20 microgauss. We propose to measure the line­of­sight field
with OH Zeeman observations toward one of their positions. This will test their interpretation, and if it is
confirmed, enable the Faraday screen technique to be used for measuring magnetic field strengths in the envelopes
of molecular clouds, greatly enhancing our ability to test the magnetic support model for star formation.
Name Institution E­mail Phone Student
Richard M. Crutcher University of Illinois crutcher@uiuc.edu 1 217 333 9581 no
Service Observing Request Remot e Observing Request
X None No
All of the observing run. Maybe
Part of the observing run. X Yes
Queue Observing
Instrument Setup
L­wide
Atmospheric Observation Instruments:
Special Equipment or setup: none
RFI Considerations
1

Frequency Ranges Planned
2