TY - JOUR

T1 - X-ray Polarization of Blazars and Radio Galaxies Measured by the Imaging X-ray Polarimetry Explorer

AU - Marscher, A.P.

AU - Di Gesu, L.

AU - Jorstad, S.G.

AU - Kim, D.E.

AU - Liodakis, I.

AU - Middei, R.

AU - Tavecchio, F.

N1 - Export Date: 01 November 2025; Cited By: 6; Correspondence Address: A.P. Marscher; Institute for Astrophysical Research, Boston University, Boston, 725 Commonwealth Ave., 01225, United States; email: marscher@bu.edu

PY - 2024

Y1 - 2024

N2 - X-ray polarization, which now can be measured by the Imaging X-ray Polarimetry Explorer (IXPE), is a new probe of jets in the supermassive black hole systems of active galactic nuclei (AGNs). Here, we summarize IXPE observations of radio-loud AGNs that have been published thus far. Blazars with synchrotron spectral energy distributions (SEDs) that peak at X-ray energies are routinely detected. The degree of X-ray polarization is considerably higher than at longer wavelengths. This is readily explained by energy stratification of the emission regions when electrons lose energy via radiation as they propagate away from the sites of particle acceleration as predicted in shock models. However, the 2–8 keV polarization electric vector is not always aligned with the jet direction as one would expect unless the shock is oblique. Magnetic reconnection may provide an alternative explanation. The rotation of the polarization vector in Mrk421 suggests the presence of a helical magnetic field in the jet. In blazars with lower-frequency peaks and the radio galaxy Centaurus A, the non-detection of X-ray polarization by IXPE constrains the X-ray emission mechanism. © 2024 Elsevier B.V., All rights reserved.

AB - X-ray polarization, which now can be measured by the Imaging X-ray Polarimetry Explorer (IXPE), is a new probe of jets in the supermassive black hole systems of active galactic nuclei (AGNs). Here, we summarize IXPE observations of radio-loud AGNs that have been published thus far. Blazars with synchrotron spectral energy distributions (SEDs) that peak at X-ray energies are routinely detected. The degree of X-ray polarization is considerably higher than at longer wavelengths. This is readily explained by energy stratification of the emission regions when electrons lose energy via radiation as they propagate away from the sites of particle acceleration as predicted in shock models. However, the 2–8 keV polarization electric vector is not always aligned with the jet direction as one would expect unless the shock is oblique. Magnetic reconnection may provide an alternative explanation. The rotation of the polarization vector in Mrk421 suggests the presence of a helical magnetic field in the jet. In blazars with lower-frequency peaks and the radio galaxy Centaurus A, the non-detection of X-ray polarization by IXPE constrains the X-ray emission mechanism. © 2024 Elsevier B.V., All rights reserved.

KW - astrophysical jets

KW - black holes

KW - high-energy processes

KW - X-ray polarization

U2 - 10.3390/galaxies12040050

DO - 10.3390/galaxies12040050

M3 - статья

VL - 12

JO - Galaxies

JF - Galaxies

SN - 2075-4434

IS - 4

ER -