AGN jets in the EHT era @Tohoku U., 20-22 Jan 2020

The radio-loud fraction oflow-luminosity HSC quasars at z~6Kianhong Lee
University of Tokyo
In collaboration withKotaro Kohno,Yoshiki Matsuoka, Tohru Nagao, Michael Strauss,
Bunyo Hatsukade, Hideki Umehata, Takuma Izumi, Malte Schramm,
Yoshiki Toba, Takuji Yamashita, Chien-Hsiu Lee, Masafusa Onoue,
Kazushi Iwasawa, Masatoshi Imanishi, Toshihiro Kawaguchi

Introduction

2 /15

Quasars’ radio properties•Quasi-stellar ‘radio’ source•

Only 10-20% (e.g., Ivezić+02) show
strong radio emission: ‘Radio-loud’•

Hints on SMBHs’ properties (e.g., mass, spin..)
シーン…
キャーーャ

キシーン…

The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

3 /15

The Kerr solution of GR— Spinning black hole•

Frame-dragging effect•Static limit→ all matter and light is forced toirresistibly rotate around the black hole•

Region within the static limit→ ergosphere•

Rotational energy can be extracted
from the ergosphere by magnetic fields(Blandford & Znajek 77)The radio-loud fraction of low-luminosity HSC quasars at z~6© Michael Cramer Andersen ‘Kerr’s rotating Black Holes’

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

4 /15Radio-loudness: two definitions•

1. Radio luminosity, e.g., logL5G= 25.5 (W/Hz)••(Jiang+07)

Just based on a critical radio luminosity for radio-loud/quiet

f5GHz
2. Radio-to-optical flux density ratio, R ≡f4400Å

(Kellermann+89)•

Extrapolating from monochromatic radio and optical data•

Assume a power-law spectral energy distribution fν ∝ ν αin both optical and radio regions•

Assumption of spectral indices:Radio: -0.75 Optical: -0.5
(Wang+07; Bañados+15)•

When R >10, classified as radio-loudThe radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

5 /15

Radio-loud fraction evolution•

Dependences of the RLF on redshift and luminosity exist?
— Jiang+07: RLF•

when redshift

and luminosity

On the other hand, the mean radio-loudness…
— White+07: Mean radio-loudness

when redshift

and luminosity•

For a more evidential result, High-z study is important! but..
— A high-z study (z>5.5, Bañados+15) shows a similar result with local studies,suggesting that there’s no such evolution.
— Probably they are biased by the luminous sample at high-z?

•We need high-z low-luminosity samples!

The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

6 /15

Radio-loud fraction evolution

100

Radio-loud fraction (%)

50

10510.5

M1450 =

27 (Jiang+07)

M1450 =

25 (Jiang+07)

M1450 =23 (Jiang+07)

1

2

3

4

5

6Redshift
The radio-loud fraction of low-luminosity HSC quasars at z~6Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

7 /15

Radio-loud fraction evolution•

Dependences of the RLF on redshift and luminosity exist?
— Jiang+07: RLF•

when redshift

and luminosity

On the other hand, the mean radio-loudness…
— White+07: Mean radio-loudness

when redshift

and luminosity•

For a more evidential result, High-z study is important! but..
— A high-z study (z>5.5, Bañados+15) shows a similar result with local studies,suggesting that there’s no such evolution.
— Probably they are biased by the luminous sample at high-z?

•We need high-z low-luminosity samples!

The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

8 /15

Radio-loud fraction evolution

100Radio-loud fraction (%)

50

105

10.5

M1450 =

27 (Jiang+07)

M1450 =

25 (Jiang+07)

M1450 =

23 (Jiang+07)

Bañados+15

123456Redshift
The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Introduction

9 /15

Radio-loud fraction evolution•

Dependences of the RLF on redshift and luminosity exist?
— Jiang+07: RLF•

when redshift

and luminosity

On the other hand, the mean radio-loudness…
— White+07: Mean radio-loudness

when redshift

and luminosity•

For a more evidential result, High-z study is important! but..
— A high-z study (z>5.5, Bañados+15) shows a similar result with local studies,suggesting that there’s no such evolution.
— Probably they are biased by the luminous sample at high-z?

•We need high-z low-luminosity samples!

The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Data

10 /15

Subaru/HSC-selected quasars•

Discovered with the Hyper Suprime-Cam Subaru Strategic Program
survey (Aihara+18)•

HSC: a wide-field image camera mounted on Subaru telescope•High-z (z~4-6)•Low-luminosity (M1450 >-26)

The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Data

11 /15

Subaru/HSC-selected quasars•Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs)(Matsuoka+16, 18ab, 19b) — 93, over 900 deg2•

Color-selected and identified with spectroscopic follow-up
observations
28

27

M1450 (mag)

26

25

24

23

22z⇠6 HSC quasars (spec-z)z⇠6 known quasars (Bañados+15)
21

5.6

5.8

6.0

6.2

6.4

6.6

6.8

7.0

Redshift© Matsuoka+18
The radio-loud fraction of low-luminosity HSC quasars at z~6Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Data

12 /15

Radio data — VLA-FIRST and JVLA follow-up••Archive•

VLA-FIRST survey (150 μJy; Becker+95)•Stripe 82 (50 μJy; Hodge+11)

Observations•

Karl G. Jansky Very Large Array (JVLA)
18A-316: March - June, 2018
19A-317: August - October, 2019•23 HSC quasars observed•

Frequency: 1.4 GHz (~20 cm)•Angular resolution: ~2”© David Akoubian•Sensitivity (1σ): ~10-50 μJy

The radio-loud fraction of low-luminosity HSC quasars at z~6Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Results

13 /15Result27.0
Radio-loud
26.5

logL5G (WHz 1)

26.0
25.5
25.0001=24.5

Rstack
24.0z⇠6 HSC quasars (JVLA)

0=1

23.5

Rz⇠6 HSC quasars (FIRST&stripe82)
Bañados+15

Radio-quiet
23.0-21-22-23-24-25-26-27-28

M1450 (mag)The radio-loud fraction of low-luminosity HSC quasars at z~6

Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Discussion

14 /15

The radio-loud fraction
Radio-loudness: critical radio luminosity
logL5G= 25.5 (W/Hz)

1001005050105Lo
re weds r
hi
ftssuonimuLF a in10.5

M1450 =

27 (Jiang+07)

M1450 =

25 (Jiang+07)

M1450 =

23 (Jiang+07)

Radio-loud fraction (%)

Radio-loud fraction (%)

f5GHz
Radio-loudness: R ≡f4400Å

t

2

50.5

3

45Redshift

6Lo
re weds rhi
ftssuonimuLF a in1Bañados+15
This work (HSC quasars)

1

10

M1450 =

27 (Jiang+07)

M1450 =

25 (Jiang+07)

M1450 =

23 (Jiang+07)

tBañados+15
This work (HSC quasars)

123456Redshift

A great fraction of SMBHs have high spin in luminous quasars?
The formation of SMBHs in the early universe makes them spin-up?
The radio-loud fraction of low-luminosity HSC quasars at z~6Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020

Summary•

We cross-matched z~6 HSC quasars with- archival radio survey (FIRST; σ = 150 μJy @1.4 GHz)and conducted- new JVLA observations (23 sources; 10-50 μJy @1.4 GHz)

•None of 93 HSC quasars are classified as radio-loud.

•The radio-loud fraction of HSC quasars at ~6:•

The radio-loud fraction of HSC quasars is lower than that of luminous
quasars.

15 /15f5GHz- 0-97% (not constraining) using R == 10 as threshold
f4400Å
- 0-5.9% using the critical radio luminosity logL5G= 25.5 (W/Hz) as threshold

The radio-loud fraction of low-luminosity HSC quasars at z~6Kianhong Lee, AGN jets in the EHT era, 22 Jan 2020