Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aj....143...32m&link_type=abstract
The Astronomical Journal, Volume 143, Issue 2, article id. 32 (2012).
Astronomy and Astrophysics
Astronomy
H Ii Regions, Ism: Clouds, Ism: Magnetic Fields, Radio Lines: Ism
Scientific paper
We have used the Very Large Array to study the Zeeman effect in 21 cm H I absorption lines from two star-forming regions in the Cygnus X complex, DR 22 and ON 2. We measure the line-of-sight magnetic field toward these regions, finding B los = -84 ± 11 μG toward the DR 22 H II region and B los < 50 μG toward each of the two H II regions in ON 2. We interpret these results in terms of two different models. In one model, we assume that the H I Zeeman effect is a measure of magnetic fields in the associated molecular clouds. If so, then the DR 22 molecular cloud is magnetically subcritical, that is, magnetically dominated. The ON 2 molecular clouds are magnetically supercritical. In a second model, we assume that the H I Zeeman effect is a measure of magnetic fields in photon-dominated regions where the gas has been compressed (and the field amplified) by absorption of stellar radiation. We find that this second model, where the measured field strength has been affected by star formation, accounts well for the DR 22 H I Zeeman effect. This same model, however, overpredicts the magnetic field in ON 2. ON 2 may be a region where the magnetic field is energetically insignificant or where the field happens to lie nearly in the plane of the sky.
Mayo Avraham E.
Troland Thomas H.
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