The Far-infrared Polarization Spectrum of œÅ Ophiuchi A from HAWC+/SOFIA 
Observations

Santos, Fabio P.; Chuss, David T.; Dowell, C. Darren; Houde, Martin; Looney, Leslie W.; Lopez Rodriguez, Enrique; Novak, Giles; Ward-Thompson, Derek; Berthoud, Marc; Dale, Daniel A.; Guerra, Jordan A.; Hamilton, Ryan T.; Hanany, Shaul; Harper, Doyal A.; Henning, Thomas K.; Jones, Terry Jay; Lazarian, Alex; Michail, Joseph M.; Morris, Mark R.; Staguhn, Johannes; Stephens, Ian W.; Tassis, Konstantinos; Trinh, Christopher Q.; Van Camp, Eric; Volpert, C. G.; Wollack, Edward J.

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Journal Article

The Far-infrared Polarization Spectrum of œÅ Ophiuchi A from HAWC+/SOFIA Observations

MPS-Authors

Santos, Fabio P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Chuss, David T.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Dowell, C. Darren
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Houde, Martin
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Looney, Leslie W.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Lopez Rodriguez, Enrique
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Novak, Giles
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Ward-Thompson, Derek
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Berthoud, Marc
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Dale, Daniel A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Guerra, Jordan A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Hamilton, Ryan T.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Hanany, Shaul
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Harper, Doyal A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Henning, Thomas K.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Jones, Terry Jay
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Lazarian, Alex
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Michail, Joseph M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Morris, Mark R.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Staguhn, Johannes
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Stephens, Ian W.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Tassis, Konstantinos
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Trinh, Christopher Q.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Van Camp, Eric
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Volpert, C. G.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Wollack, Edward J.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

External Resource

https://ui.adsabs.harvard.edu/abs/2019ApJ...882..113S
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Citation

Santos, F. P., Chuss, D. T., Dowell, C. D., Houde, M., Looney, L. W., Lopez Rodriguez, E., et al. (2019). The Far-infrared Polarization Spectrum of œÅ Ophiuchi A from HAWC+/SOFIA Observations. The Astrophysical Journal, 882.

Cite as: https://hdl.handle.net/21.11116/0000-0005-D264-D

Abstract

We report on polarimetric maps made with HAWC+/SOFIA toward œÅ Oph A, the densest portion of the œÅ Ophiuchi molecular complex. We employed HAWC+ bands C (89 Œºm) and D (154 Œºm). The slope of the polarization spectrum was investigated by defining the quantity {{ \mathcal R }}_{DC}={p}_D/{p}_C, where p _C and p _D represent polarization degrees in bands C and D, respectively. We find a clear correlation between {{ \mathcal R }}_{DC} and the molecular hydrogen column density across the cloud. A positive slope ({{ \mathcal R }}_{DC} > 1) dominates the lower-density and well-illuminated portions of the cloud, which are heated by the high-mass star Oph S1, whereas a transition to a negative slope ({{ \mathcal R }}_{DC} < 1) is observed toward the denser and less evenly illuminated cloud core. We interpret the trends as due to a combination of (1) warm grains at the cloud outskirts, which are efficiently aligned by the abundant exposure to radiation from Oph S1, as proposed in the radiative torques theory; and (2) cold grains deep in the cloud core, which are poorly aligned owing to shielding from external radiation. To assess this interpretation, we developed a very simple toy model using a spherically symmetric cloud core based on Herschel data and verified that the predicted variation of {{ \mathcal R }}_{DC} is consistent with the observations. This result introduces a new method that can be used to probe the grain alignment efficiency in molecular clouds, based on the analysis of trends in the far-infrared polarization spectrum.