English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

Low optical polarization at the core of the optically thin jet of M87

MPS-Authors
/persons/resource/persons247184

Fresco,  A. Y.
High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4724

Merloni,  A.
High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;

External Ressource
No external resources are shared
Fulltext (public)
There are no public fulltexts stored in PuRe
Supplementary Material (public)
There is no public supplementary material available
Citation

Fresco, A. Y., Fernández-Ontiveros, J. A., Prieto, M. A., Acosta-Pulido, J. A., & Merloni, A. (2020). Low optical polarization at the core of the optically thin jet of M87. Monthly Notices of the Royal Astronomical Society, 496(2), 2204-2212. doi:10.1093/mnras/staa1566.


Cite as: http://hdl.handle.net/21.11116/0000-0007-5343-0
Abstract
We study the optical linear and circular polarization in the optically thin regime of the core and jet of M87. Observations were acquired two days before the Event Horizon Telescope (EHT) campaign in early 2017 April. A high degree (∼20 per cent) of linear polarization (Plin) is detected in the bright jet knots resolved at ∼10 to 23 arcsec (⁠0.8−1.8 kpc⁠) from the centre, whereas the nucleus and inner jet show Plin≲ 5 per cent. The position angle of the linear polarization shifts by ∼90° from each knot to the adjacent ones, with the core angle perpendicular to the first knot. The nucleus was in a low level of activity (Plin∼ 2–3 per cent), and no emission was detected from HST-1. No circular polarization was detected either in the nucleus or the jet above a 3 σ level of Pcirc ≤ 1.5 per cent, discarding the conversion of Plininto Pcirc. A disordered magnetic field configuration or a mix of unresolved knots polarized along axes with different orientations could explain the low Plin. The latter implies a smaller size of the core knots, in line with current interferometric observations. Polarimetry with EHT can probe this scenario in the future. A steep increase of both Plin and Pcirc with increasing frequency is expected for the optically thin domain, above the turnover point. This work describes the methodology to recover the four Stokes parameters using a λ/4 waveplate polarimeter.