CTAで探る低光度AGN電波シェルからの超高エネルギーガンマ線放射
γCTAγ

SKA

紀 基樹 (国立天文台)
１０月からISAS/JAXA
高エネルギーガンマ線でみる極限宇宙2012

1Content
1. Introduction
2. Model3. Application to nearby mini bubbles
4. Results
1. Mini shell as new class of VHE γ emitter (Leptonic)
MK, Ito, Kawakatu & Orienti (2012), ApJ, submitted

2. VHE γ afterlight from mini radio-lobe (Hadronic)
MK & Asano (2011) MNRAS Letters

5. Summary
2Introduction

3What are shells & radio lobes?
Jets are enveloped in a cocoon consisting of shocked jet material and the cocoon is surroundedby shocked interstellar medium. The shocked ambient region is identical to the shell

AGN jets are known as powerful particle accelerators.
4

Shell is known as dark viewed in radio5Model6

Shell Dynamics
Dynamics: we adopt well-established bubble model (Castor 1975; Ostriker & McKee 1988).
The shell width at the bubble radius $R$ is denoted as δR.

Non-thermal photons and electrons: We solve the following kinetic equation describing theelectron energy distribution as follows:

Regarding IC scattering, the following seed photons are included:(1) UV photons from a standard accretion disk
(2) IR photons from a dust torus(3) synchrotron photons from the radio lobes(4) synchrotron photons from the shell7Proton Acceleration In Hot Spots
Assuming proton-gyro factor ξp

hot spot (hs)jetpp p~102 ,MK & Asano (2011)

Acceleration time
Cooling time

reverse shock
Confinement condition

Hot spots can accelerate protons
up to ~10^18eV (when ξp ~102).
8

Proton injection into radio lobes
MK & Asano (2011)

radio lobeppp
jetSideways escape velocityppp

Sideways escape timeppp

High energy protons produced at the hot spot
are injected (escaped) into the radio lobes.
9Application to nearby minibubbles
10

Targets: Nearby Compact Radio Sources (~a few pc size)
CORALZ list: De Vries+09

1. Compact RAdio sources in Low-Z (CORALZ)
Snellen+; de Vries+
0.005<z<0.16
Θ< 2 arcsec
S_1.4GHz >100 mJy in FIRST catalogue.

2. Less-Luminous CORALZ•Deeper survey of CORALZ in the future
S _1.4GHz >1~100 mJy in FIRST catalogue•A new (unbiased) survey by SKA in the future11Jet Power, Ambient matter density etc.
Jet power: Since the SSA turnover frequency, the flux and the size of the radio lobe
are observationally determined, B_lobe is well constraint. Therefore, we canestimate the the jet power from these quantities.

Shell and lobe parameters: Shell parameters can be well constrained by the wellstudied supernovae remnants. Lobe parameters are determined by the various
observations of the lobes.

12Estimate of nucleus luminosity: LIR & LUV
Since disk's UV emission is likely a main source for the ionizationof clouds in narrow line regions, it is reasonable to suppose that LUV > L[OIII]
Kunert-Bajraszawska+ 2010

L[OIII]~ 1040-43 erg/s

Calderone+ 2012

LIR~(1/3-1/2) LUVWe adopt
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Results: VHE γ from mini-shell

14

Resultant Spectra

We find that the non-thermal emission from the mini-shells canbe detectable by CTA and they become a potential newclass of VHE gamma-ray emitters.

15

IC seed: lobe-synchrotron-dominated
The shell luminosity at TeV range becomes slightly brighter whensynchrotron emission of radio lobes become brighter.

Luv=2L_ir =6*10^42 erg/s

16

IC seed: nucleus-dominated
The shell luminosity at TeV range remains constant because
IC scattering is dominated by nucleus emission .

Luv=2L_ir =6*10^42 erg/s17

Results: VHE γ from mini-radiolobes
18What if the a jet stops within a few ten years?
Suzuki, Nagai, MK+ 2012？
電波観測屋にとっては嬉しくないが．．

New-born lobe: NGC1275

19

Hadronic Afterlight
MK & Asano (2011)@100Mpc
CTAのターゲット！

陽子
シンクロ
２次生成
電子シンクロ電波ダークなローブ。CTAでの検出可能性有。

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SummaryWe have studied non-thermal emissions from mini radio lobes and shells(CORALZs & less luminous CORALZs). Since the energy densities ofsoft photons from AGN nucleus and synchrotron photons from the radio
lobe are large, emissions both from the mini-shells and mini-lobe can bedetectable by CTA and can be new class of VHE emitters.
•IC emission from the mini-shell overwhelms the emission from the radio
lobe in VHE range.
MK, Ito, Kawakatu & Orienti (2012), ApJ Letters, submitted•

When the jet stops within ~100years, hadronic (pγ) afterlight emission
from the mini radio lobe can be seen in VHE range.
MK & Asano (2011) MNRAS Letters21

Buck up22

γγ => e+ e- absorption（R=5pc）
We include the effect of absorption via gamma
gamma ->e+e- interaction.VHE photons
suffer from the gamma/gamma absorption via
interaction with various soft photons.
The γγ absorption opacity against the intrinsic
photons (tau_{gamma-gamma}) can becalculated by summing up all of the photonsfrom(1) the shell (negligibly small),(2) the radio lobes,(3) the dusty torus, and(4) the accretion diskand we multiply the γγ absorption factor of exp(-τ_γγ) to the unabsorbed flux. We adopt themodel of Franceschini et al. (2008).

At the frequency below ~10^26 Hz, the number density oftarget photons from radio lobes is larger than that from the shell,
therefore the lobe photons govern the absorption opacity.
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What happens for C.R.-filled lobes?
accretion
disk

radio lobe

p pp

jet

p p
p

hot spot
LS= 10pc

pγ cascade in the mini radio lobe!

24Predicted photon spectra
太線：陽子入り細線：陽子無し@100Mpc
SSA吸収
電子シンクロγγ吸収

陽子シンクロ

２次生成電子シンクロ25

Predicted photon spectra
太線：陽子入り細線：陽子無し@100Mpc

SSA吸収

陽子シンクロ

２次生成電子シンクロ

抜け出せた２γ26

Cascade and cooling process(π 中間子生成)(π 中間子崩壊)(γ γ 吸収)(Bethe-Heitler過程)
Synchrotron and Inverse-Compton of charged particles
Synchrotron-Self-Absorption (SSA)
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