Optical Polarimetry of the Jets of Nearby Radio Galaxies. I. The Data

Perlman, Eric S.; Padgett, C. A.; Georganopoulos, Markos; Sparks, W. B.; Biretta, J. A.; O’Dea, C. P.; Baum, Stefi A.; Birkinshaw, Mark; Worrall, D. M.; Dulwich, Fred; Jester, Sebastian; Martel, A. R.; Capetti, A.; Leahy, J. P.

doi:10.1086/506587

Cited by 34 publications

(51 citation statements)

References 91 publications

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“…In addition to the polarization in the nuclei and from the large scale optical jets (which are presented elsewhere, Perlman et al 2006), regions of extended polarized emission are also detected. They are closely cospatial with dust features (mainly taking the form of dusty circumnuclear disks) indicative of polarization due to dichroic transmission.…”

Section: Summary and Discussionmentioning

confidence: 74%

On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry

Capetti¹,

Axon

Chiaberge

et al. 2007

A&A

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We obtained optical imaging polarimetry with the ACS/HRC aboard the HST of the 9 closest radio-galaxies in the 3C catalogue with an FR I morphology. The nuclear sources seen in direct HST images in these galaxies are found to be highly polarized with levels in the range ∼2-11% with a median value of 7%. We discuss the different mechanisms that produce polarized emission and conclude that the only viable interpretation is a synchrotron origin for the optical nuclei. This idea is strengthened by the analogy with the polarization properties of BL Lac objects, providing also further support to the FR I/BL Lac unified model. This confirms previous suggestions that the dominant emission mechanism in low luminosity radio-loud AGN is related to non-thermal radiation produced by the base of their jets. In addition to the nuclear polarization (and to the large scale optical jets), polarization is detected co-spatially with the dusty circumnuclear disks, likely due to dichroic transmission; the polarization vectors are tangential to the disks as expected when the magnetic field responsible for the grains alignment is stretched by differential rotation. We explored the possibility to detect the polarimetric signature of a misaligned radiation beam in FR I, expected in our sources in the frame of the FR I/ BL Lac unification. We did not find this effect in any of the galaxies, but our the results are not conclusive on whether a misaligned beam is indeed present in FR I.

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Section: Summary and Discussionmentioning

confidence: 74%

On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry

Capetti¹,

Axon

Chiaberge

et al. 2007

A&A

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“…At the shortest wavelengths of the MIR spectrum the stellar population of the host galaxy can be seen. 3C66B has an arcsecond-scale jet (Hardcastle et al 1996) which is also seen in the optical (Butcher et al 1980;Macchetto et al 1991;Perlman et al 2006), in X-rays (Hardcastle et al 2001), and even at MIR wavelengths a detection with Infrared Space Observatory (ISO) is claimed (Tansley et al 2000). However, unlike the case of 3C15, the jet in 3C66B is weaker than the core.…”

Section: Notesmentioning

confidence: 98%

THESPITZERVIEW OF FR I RADIO GALAXIES: ON THE ORIGIN OF THE NUCLEAR MID-INFRARED CONTINUUM

Leipski

Antonucci

Ogle

et al. 2009

ApJ

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We present Spitzer mid-infrared (MIR) spectra of 25 FR I radio galaxies and investigate the nature of their MIR continuum emission. MIR spectra of star-forming galaxies and quiescent elliptical galaxies are used to identify host galaxy contributions while radio/optical core data are used to isolate the nuclear nonthermal emission. Out of the 15 sources with detected optical compact cores, four sources are dominated by emission related to the host galaxy. Another four sources show signs of warm, nuclear dust emission: 3C15, 3C84, 3C270, and NGC 6251. It is likely that these warm dust sources result from hidden active galactic nuclei of optical spectral type 1. The MIR spectra of seven sources are dominated by synchrotron emission, with no significant component of nuclear dust emission. In parabolic spectral energy distribution fits of the nonthermal cores FR Is tend to have lower peak frequencies and stronger curvature than blazars. This is roughly consistent with the common picture in which the core emission in FR Is is less strongly beamed than in blazars.

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“…The low polarization in the optical is not necessarily unusual in the context of a synchrotron model (especially given the rather high upper limit), since synchrotron emission can still be produced in an environment with a 'tangled' magnetic field which produces linear polarization that effectively cancels out. However, it is somewhat unusual to find that a jet with reasonably high radio polarization lacks polarization in the optical (see, e.g., Perlman et al 1999Perlman et al , 2006. Deeper optical polarization observations are necessary to get more stringent limits on the optical polarization degree, before any strong conclusions can be drawn about the nature of the optical emission.…”

Section: Optical and Radio Polarizationmentioning

confidence: 99%

Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84

Meyer

Πετροπούλου

Georganopoulos

et al. 2018

ApJ

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We report an optical/UV jet and counterjet in M84, previously unreported in archival HST imaging. With archival VLA, ALMA, and Chandra imaging, we examine the first well-sampled spectral energy distribution of the inner jet of M84, where we find that multiple co-spatial spectral components are required. In particular, the ALMA data reveal that the radio spectrum of all four knots in the jet turns over at approximately 100 GHz, which requires a second component for the bright optical/UV emission. Further, the optical/UV has a soft spectrum and is inconsistent with the relatively flat X-ray spectrum, which indicates a third component at higher energies. Using archival VLA imaging, we have measured the proper motion of the innermost knots at 0.9±0.6 and 1.1±0.4c, which when combined with the low jet-to-counterjet flux ratio yields an orientation angle for the system of 74 +9 −18• . In the radio, we find high fractional polarization of the inner jet of up to 30% while in the optical no polarization is detected (< 8%). We investigate different scenarios for explaining the particular multi-component SED of the knots. Inverse Compton models are ruled out due to the extreme departure from equipartition and the unrealistically high total jet power required. The multi-component SED can be naturally explained within a leptohadronic scenario, but at the cost of very high power in relativistic protons. A two-component synchrotron model remains a viable explanation, but more theoretical work is needed to explain the origin and properties of the electron populations.

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Optical Polarimetry of the Jets of Nearby Radio Galaxies. I. The Data

Cited by 34 publications

References 91 publications

On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry

On the nature of optical nuclei in FR I radio-galaxies from ACS/HST imaging polarimetry

THESPITZERVIEW OF FR I RADIO GALAXIES: ON THE ORIGIN OF THE NUCLEAR MID-INFRARED CONTINUUM

Detection of an Optical/UV Jet/Counterjet and Multiple Spectral Components in M84

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