Diverse Polarimetric Features of AGN Jets from Various Viewing Angles Towards a Unified View

2025-05-04 0 0 2.61MB 11 页 10玖币

侵权投诉





Citation: Tsunetoe, Y.; Mineshige, S.;

Kawashima, T.; Ohsuga, K.; Akiyama,

K.; Takahashi, H.R. Diverse

Polarimetric Features of AGN Jets

from Various Viewing Angles:

Towards a Uniﬁed View. Preprints

2022,10, 103. https://doi.org/

10.3390/galaxies10050103

Academic Editor: Luigina Feretti

Publisher’s Note: MDPI stays neutral

with regard to jurisdictional claims in

published maps and institutional afﬁl-

iations.

Licensee MDPI, Basel, Switzerland.

This article is an open access article

distributed under the terms and

conditions of the Creative Commons

Attribution (CC BY) license (https://

creativecommons.org/licenses/by/

4.0/).

Article

Diverse Polarimetric Features of AGN Jets from Various Viewing

Angles: Towards a Uniﬁed View

Yuh Tsunetoe 1,* , Shin Mineshige 1, Tomohisa Kawashima 2, Ken Ohsuga 3, Kazunori Akiyama 4,5,6 and

Hiroyuki R. Takahashi 7

1Department of Astronomy, Kyoto University, Kyoto 606-8501, Japan

2Institute for Cosmic Ray Research, University of Tokyo, Tokyo 113-8654, Japan

3Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8577, Japan

4Haystack Observatory, Massachusetts Institute of Technology, 99 Millstone Road MA 01886, USA

5Black Hole Initiative, Harvard University, 20 Garden Street, Cambridge MA 02138, USA

6National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka-shi Tokyo, 181-8588, Japan

7Department of Natural Sciences, Faculty of Arts and Sciences, Komazawa University, Tokyo 154-8525, Japan

*Correspondence: tsunetoe@kusastro.kyoto-u.ac.jp

Abstract:

Here, we demonstrate that polarization properties show a wide diversity depending on viewing

angles. To simulate images of a supermassive black hole and surrounding plasma, we performed a

full-polarimetric general relativistic radiative transfer based on three-dimensional general relativistic

magnetohydrodynamics models with moderate magnetic strengths. Under an assumption of a hot-jet

and cold-disk in the electron temperature prescription, we conﬁrmed a typical scenario where polarized

synchrotron emissions from the funnel jet experience Faraday rotation and conversion in the equatorial

disk. Further, we found that linear polarization vectors are inevitably depolarized for edge-on-like

observers, whereas a portion of vectors survive and reach the observers in face-on-like cases. We also

found that circular polarization components have persistent signs in the face-on cases, and changing

signs in the edge-on cases. It is conﬁrmed that these features are smoothly connected via intermediate

viewing-angle cases. These results are due to Faraday rotation/conversion for different viewing angles,

and suggest that a combination of linear and circular polarimetry can give a constraint on the inclination

between the observer and black hole’s (and/or disk’s) rotating-axis and plasma properties in the jet–disk

structure. These can also lead to a more statistical and uniﬁed interpretation for a diversity of emissions

from active galactic nuclei.

Keywords:

black hole physics; accretion disks; active galactic nuclei; radio jets; radiative transfer;

polarimetry

1. Introduction

The direct images of supermassive black holes (SMBH) M87* and Sgr A* by the Event

Horizon Telescope (EHT) have opened a new era of black hole studies [

]. In particular,

the polarimetric images around the black holes have attracted attention as they can reﬂect

the conﬁguration of magnetic ﬁelds around the SMBH [

]. It has been established from

theoretical approaches that the magnetic ﬁelds should have an important role in the creation

and acceleration of the jets from active galactic nuclei (AGNs) hosting the SMBHs [

]. We can

thus expect to shed new light on the long-standing question of the driving mechanism of AGN

jets through these unprecedented high-resolution observations.

However, one should also note that the polarized synchrotron emissions from a SMBH

can experience Faraday effects on the way to Earth. Observational studies have detected traces

of signiﬁcant Faraday rotation of the linear polarization (LP) vectors in a range of millimeter

and submillimeter wavelengths for many AGNs with/without jets [

–

]. It has been pointed

out by theoretical studies that these should be attributed to internal Faraday rotation; that is,

arXiv:2210.12162v1 [astro-ph.HE] 21 Oct 2022

2 of 11

Figure 1.

A schematic picture of the jet–disk structure (adopted from Tsunetoe et al.

[18]

). In our

model, synchrotron emission is predominantly produced in the funnel jet (green). After the emission,

the polarized lights experience Faraday conversion in the inner hot disk (red) and Faraday rotation in the

outer cold disk (blue) on the way to the observer (eyeball), respectively. See [

] for poloidal-slice maps

of typical values of the emissivity and Faraday coefﬁcients.

the Faraday rotation should occur in tandem with the emission near an SMBH, e.g., [

–

Furthermore, recent calculations have demonstrated that signiﬁcant Faraday conversion from

LP to circular polarization (CP) can occur near a SMBH [

]. In such cases, CP components

of the combination between the intrinsic emission and conversion from LP components can be

a good tool for investigating the magnetic ﬁeld structure.

In this way, it has been established that the uniﬁed interpretation of both LP and CP is

essential for understanding the magnetic structure and other plasma properties around an

SMBH. In this context, we have thought of calculating the polarization images theoretically.

To predict images around and near a BH, we must take general relativistic (GR) effects into

account, and, here, perform the GR radiative transfer (GRRT) calculation based on the GR

magnetohydrodynamics (GRMHD) models, e.g., [15–17].

In the previous work Tsunetoe et al.

[18]

, we conﬁrmed, on the basis of our moderately

magnetized models with a hot jet and cold disk, a scenario where the polarized emissions

produced in the jet experience the Faraday rotation and conversion effects in the disk. In this

description of the emitting jet and Faraday-thick disk, we found that the LP (or CP) intensities

Parameter Value

BH mass M•6.5 ×109M

BH spin parameter a0.9375

Magnetic ﬂux on the horizon φ≈18 (semi-MAD)

Te-parameter Rlow 1

Te-parameter Rhigh 73

Mass accretion rate onto BH ˙

M6×10−4Myr−1(at the moment of snapshot)

Distance to observer D16.7 Mpc

Observational frequency ν230 GHz

Table 1.

Parameters in our GRMHD and GRRT model, following a ﬁducial model in [

], except the

observer’s inclination angle. Here,

M

is the solar mass.

φ≡ΦBH/q˙

Mrgc2

is a strength of dimensionless

magnetic ﬂux on the event horizon of SMBH, where

rg≡GM•/c2

and

ΦBH = (

)R R |Br|

Aθφ

and care the gravitational constant and speed of light, respectively.

3 of 11

Figure 2.

A calculated polarization images at 230 GHz for three viewing angles of

◦

(nearly

face-on), 50

◦

(intermediate), and 90

◦

(edge-on), top to bottom. (

Left

) Total intensity (Stokes

) image.

Each image consists of 600

600 pixels. The forward jet extends upward on the image. (

Center

) LP map.

The LP intensity is shown by the color contour, with LP vectors in electric vector position angle (EVPA)

overwritten. (

Right

) CP image. The CP intensity (Stokes

) is shown by the color contour with sign. A

movie of all the images for

◦−

180

◦

can be found on https://youtu.be/065qAx6Tff0 (accessed on

October 19, 2022).

are mainly distributed in the downstream (upstream) side of the approaching jet for nearly face-

on observers. In this work, we surveyed polarimetric features for different inclination angles

between the black hole’s spin-axis and an observer, to expand and develop the discussions.

Here, we bore in mind observations of a diverse range of AGN jets at 230 GHz by the EHT and

other very long baseline interferometers (VLBIs). Furthermore, we thought of applying them

to the interpretation of the disk precession around SMBHs [19,20].

2. Methods

We followed the model parameters adopted in the ﬁducial model in [

]. Here, we used a

three-dimensional GRMHD model simulated with

UWABAMI

code [

], which is categorized

into the intermediary area between a magnetically arrested disk (MAD; [

]) and standard and

normal evolution (SANE; [

]), and is thus called semi-MAD. The

R−β

model was adopted

for the determination of electron temperature, where the proton–electron temperature ratio

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

Citation:Tsunetoe,Y.;Mineshige,S.;Kawashima,T.;Ohsuga,K.;Akiyama,K.;Takahashi,H.R.DiversePolarimetricFeaturesofAGNJetsfromVariousViewingAngles:TowardsaUniedView.Preprints2022,10,103.https://doi.org/10.3390/galaxies10050103AcademicEditor:LuiginaFerettiPublisher'sNote:MDPIstaysneutralwithregardtojuri...

展开>> 收起<<

Diverse Polarimetric Features of AGN Jets from Various Viewing Angles Towards a Unified View.pdf

共11页,预览3页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

Diverse Polarimetric Features of AGN Jets from Various Viewing Angles Towards a Unified View

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: