Multi-Wavelength Polarimetry and Spectral Study of the M87 Jet During 2002–2008*

Abstract

We present a multi-wavelength polarimetric and spectral study of M87 jet obtained at sub-arcsecond resolution between 2002 and 2008. The observations include multi-band archival VLA polarimetry data sets along with the HST imaging polarimetry. These observations have better angular resolution than previous work by factors of 2-3 and in addition, allow us to explore the time domain. These observations envelope the huge flare in HST-1 located at 0. 86 from the nucleus (Cheung et al. 2007;Harris et al. 2009;Madrid 2009;Perlman et al. 2011). The increased resolution enables us to view more structure in each knot, showing several resolved sub-components. We also see apparent helical structure in the polarization vectors in several knots, with polarization vectors turning either clockwise or counterclockwise near the flux maxima in various places as well as show filamentary undulations. Some of these characteristics are correlated with flux and polarization maxima while others are not. We also examine the total flux and fractional polarization and look for changes in both radio and optical since the observations of Perlman et al. (1999) and test them against various models based on shocks and instabilities in the jet. Our results are broadly consistent with previous spine-sheath models and recollimation shock models, however, they require additional combinations of features to explain the observed complexity, e.g. shearing of magnetic field lines near the jet surface and compression of the toroidal component near shocks. In particular, in many regions we find apparently helical features both in total flux and polarization. We discuss the physical interpretation of these features.

Flux variability from ejecta in structured relativistic jets with large-scale magnetic fields

“…Seen at large angles, the slower layer is more Doppler boosted than the spine, leading to the appearance of a distinctive radio structure of an "empty pipe". Observations of a different magnetic structure of the inner and outer jets via polarization measurements (Gabuzda et al 2014;Avachat et al 2016;Giroletti et al 2004) support the idea that the two jet components may be launched from different processes, such as those proposed by Blandford & Znajek (1977) and Blandford & Payne (1982), for launching from the vicinity of the rotating supermassive black hole or from the accretion disk.…”

A small satellite version of a soft x-ray polarimeter

“…Jet and shock models predict different B-field directions and, consequently, PA. For knots in a laminar jet flow, B can be nearly parallel to the jet axis, 24,25 while for shocks B should be perpendicular. 26 Both cases were observed in the optical and radio polarimetry of the M 87 jet, 27,28 indicating highly ordered magnetic fields in regions that also produce X-ray emission. 29 To allow for low ordering as observed in the UV for some HSPs, we require MDPs ≤ 10%.…”

A new method for extending solutions to the self-similar relativistic magnetohydrodynamic equations for black hole outflows

“…Indeed, as shown by various works, e.g. Perlman et al (1999); Avachat et al (2016); Russell & Shahbaz (2014), multiwavelength polarisation studies can help constrain the magnetic field morphology over large scales. The parameter degeneracy in the evaluation of the spectral energy distribution of the given source is also greatly reduced by polarisation measurements.…”