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Proposal Identification No.:

A1901

Date Received:

2004-Jan-29 18:49:22

Technical Page
Proposal Type: General Category: Sub-Category: Observation Category: Total Time Requested: Prop osal Title: ABSTRACT: Regular Astronomy Spectroscopy Galactic 20 Hours

OH Zeeman Test of Faraday Rotation in Dark Cloud Envelopes

The magnetic supp ort mo del for star formation has ambip olar diffusion increasing the mass-to-magnetic flux ratio in cores until they b ecome magnetically sup ercritical and collapse. The mo del absolutely requires that envelop es b e sub critical. Previous OH Zeeman measurements were p ointed toward cores and do not address whether envelop es are sub critical. Recently Wollenb en and Reich interpreted low synchrotron p olarization found at the b oundaries of nearby molecular clouds as b eing due to Faraday screens pro duced by Faraday rotation in the envelop es of these clouds. They inferred line-of-sight field strengths of 20 microgauss. We prop ose to measure the line-of-sight field with OH Zeeman observations toward one of their p ositions. This will test their interpretation, and if it is confirmed, enable the Faraday screen technique to b e used for measuring magnetic field strengths in the envelop es of molecular clouds, greatly enhancing our ability to test the magnetic supp ort mo del for star formation.

Name Richard M. Crutcher

Institution University of Illinois

E-mail crutcher@uiuc.edu

Phone 1 217 333 9581

Student no

Service Observing Request

Remot e Observing Request

X

None All of the observing run. Part of the observing run. Queue Observing X

No Maybe Yes

Instrument Setup
L-wide Atmospheric Observation Instruments:

Sp ecial Equipment or setup:

none

RFI Considerations
1


Frequency Ranges Planned

2