Title: Kink-driven magnetic reconnection in relativistic jets: consequences for X-ray polarimetry of BL Lacs

Abstract

ABSTRACT We investigate with relativistic MHD (magnetohydrodynamic) simulations the dissipation physics of BL Lac jets, by studying the synchrotron polarization signatures of particles accelerated by the kink instability in a magnetically dominated plasma column. The non-linear stage of the kink instability generates current sheets, where particles can be efficiently accelerated via magnetic reconnection. We identify current sheets as regions where s = Jδ/B is above some predefined threshold (where B is the field strength, J is the current density, and δ is the grid scale), and assume that the particle injection efficiency scales as ∝J2. X-ray emitting particles have short cooling times, so they only probe the field geometry of their injection sites. In contrast, particles emitting in the optical band, which we follow self-consistently as they propagate away from their injection sites while cooling, sample a larger volume, and so they may be expected to produce different polarimetric signatures. We find that the degree of polarization is roughly the same between X-ray and optical bands, because even the optical emitting particles do not travel far from the current sheet where they were injected, due to lack of sufficient kink-generated turbulence. The polarization angle shows a different temporal evolution betweenmore » the two bands, due to the different regions probed by X-ray and optical emitting particles. In view of the upcoming IXPE satellite, our results can help constrain whether kink-induced reconnection (as opposed to shocks) can be the source of multiwavelength emission from BL Lacs.« less

Authors:

Bodo, G.  ^[1];

• Search DOE PAGES for author "Bodo, G."
• Search DOE PAGES for ORCID "0000-0002-9265-4081"

Tavecchio, F. ^[2]; Sironi, L. ^[3]

---

+ Show Author Affiliations

1. INAF – Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese, Italy
2. INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate, Italy
3. Department of Astronomy and Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA

Publication Date:

Sat Nov 21 00:00:00 EST 2020

Research Org.:

Columbia Univ., New York, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1759133

Alternate Identifier(s):

OSTI ID: 1852292

Grant/Contract Number:  

SC0016542

Resource Type:

Published Article

Journal Name:

Monthly Notices of the Royal Astronomical Society

Additional Journal Information:

Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 501 Journal Issue: 2; Journal ID: ISSN 0035-8711

Publisher:

Oxford University Press

Country of Publication:

United Kingdom

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics; magnetic reconnection; radiation mechanisms: non-thermal; X-rays: galaxies