Faraday Rotation Measure Gradients from a Helical Magnetic Field in 3C273

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Using high frequency (12-22 GHz) VLBA observations we confirm the existence of a Faraday rotation measure gradient of {approx}500 rad m{sup -2} mas{sup -1} transverse to the jet axis in the quasar 3C273. The gradient is seen in two epochs spaced roughly six months apart. This stable transverse rotation measure gradient is expected if a helical magnetic field wraps around the jet. The overall order to the magnetic field in the inner projected 40 parsecs is consistent with a helical field. However, we find an unexpected increase in fractional polarization along the edges of the source, contrary to expectations. This ... continued below

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11 pages

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Zavala, Robert T.; /Naval Observ., Flagstaff; Taylor, G.B. & /NRAO, Socorro /KIPAC, Menlo Park June 6, 2005.

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Using high frequency (12-22 GHz) VLBA observations we confirm the existence of a Faraday rotation measure gradient of {approx}500 rad m{sup -2} mas{sup -1} transverse to the jet axis in the quasar 3C273. The gradient is seen in two epochs spaced roughly six months apart. This stable transverse rotation measure gradient is expected if a helical magnetic field wraps around the jet. The overall order to the magnetic field in the inner projected 40 parsecs is consistent with a helical field. However, we find an unexpected increase in fractional polarization along the edges of the source, contrary to expectations. This high fractional polarization rules out internal Faraday rotation, but is not readily explained by a helical field. After correcting for the rotation measure, the intrinsic magnetic field direction in the jet of 3C273 changes from parallel to nearly perpendicular to the projected jet motion at two locations. If a helical magnetic field causes the observed rotation measure gradient then the synchrotron emitting electrons must be separate from the helical field region. The presence or absence of transverse rotation measure gradients in other sources is also discussed.

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11 pages

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  • Journal Name: Astrophys.J.626:L73-L76,2005

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  • Report No.: SLAC-PUB-10993
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 890469
  • Archival Resource Key: ark:/67531/metadc876030

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  • June 6, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Dec. 5, 2016, 3:48 p.m.

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Zavala, Robert T.; /Naval Observ., Flagstaff; Taylor, G.B. & /NRAO, Socorro /KIPAC, Menlo Park. Faraday Rotation Measure Gradients from a Helical Magnetic Field in 3C273, article, June 6, 2005; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc876030/: accessed August 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.