radio properties of bal quasars

Radio properties of BAL quasars

Takayuki HAYASHI (Univ. Tokyo , NAOJ/VLBI)

Akihiro Doi (ISAS/JAXA) Hiroshi Nagai (ALMA/NAOJ)

Broad Absorption Line (BAL) quasars– Blue-shifted absorption line (e.g., CIV, Mg II) at rest UV

• Many sources are found at z~2– It is broad : – It has large velocity :

– ~15% of SDSS quasars show BAL (SDSS DR5, Gibson+ 2009)

⇒ thermal accretion disk wind is absorber?

Gregg+ 2000

CIV

2

Proga+ 2000

Introduction 1 :

Disk winddisk

Galaxy evolution and BAL quasars– The disk wind could suppress star formation– BAL works as AGN feedback in the course of galaxy

evolution?

Pure disk galaxy

Pseudo-bulge

No correlation betweenBH and bulge mass

Major merger Starburst, buried quasar ?

Quasar phase

Classical bulge

ElllipticalCorrelation between BH

mass and bulge mass

BAL works as AGN feedback to

the galaxy ??(Kormendy+ 2011)

Hopkins+

BAL

Introduction 1 :

4

Current issue: which is dominant ?– Difference of the viewing angle

– Difference of the central engine

BAL fraction suggests

covering factor

BAL fraction suggests time possessing the

wind

disk wind ： v ～ 0.1c

disk wind ： v ～ 0.1c

Introduction 1 :

Radio studies for BAL quasars is meaningful !!– The state of the disk can be obtained through radio jet

Do BAL quasars and non-BAL quasars have a same central engine??

– Viewing angle to the sources can be determined• Morphology• Spectral index

Introduction 2 :

Osuga+ 2011

NGC1052 NRAO/AUI

Edge-on 3C380 Kameno+

pole-on

Radio spectrum and orientation of the source

Introduction 2 :

3C175 NRAO

Orientation

Spe

ctra

l ind

ex

Fine+ 2011

Flux

Frequency

Flux

Frequency

NGC1052 NRAO/AUI

Edge-on 3C380 Kameno

pole-on

lobe lobe

core core

Radio spectral index depends on the orientation

Radio Properties of BAL quasars– ~ 1990s (before SDSS and FIRST)

• No radio-loud BAL quasars was found (Stock+ 1992)– 2000s ~ (after SDSS and FIRST)

• BAL quasars are moderately radio loud (Becker+ 2000, 2001)

• Large scale, FR2-BAL quasars are rare (Gregg+ 2000, 2006)• BAL quasars are steeper than non-BAL quasars (DiPompeo+

2011)

Introduction 2 :

cutoff

Shankar+ 2008

DiPompeo+ 2011

steep flat/inverted

What does the distribution indicate ?

difference of the central engine ?

orthe viewing angle ?

Radio Spectral Index of BAL quasars

Spectral index can be explained byviewing angle ?

Introduction 2 :

DiPompeo+ 2011, 2012

steep flat/inverted

Basic information– SDSS DR5 quasars at

• CVI BAL quasars from Gibson+ 2009• Constructing Radio loud quasars catalog using VLA FIRST

survey(Selecting radio sources within 3 arcsec of each quasar)

Statistical Study : Sample

Radio Quiet Radio Loud with core

non CVI BAL 22,893 1,874CVI BAL 3,540 292

Luminosity distribution– Assuming Spectral index at 1.4-5 GHz,

obtained by DiPompeo+ 2011

– Reducing 5-GHz Luminosity

Statistical Study : SampleDiPompeo+ 2011

Assumption– Assuming

• Power-low distribution of Lorentz factor ; ,

• Viewing angle of non-BAL quasars ;

• Viewing angle of BAL quasars is ;

Then Doppler factor is obtained as;

• No correlation between and

Study 1: Monte-Carlo Simulation

Schematic picture

Study 1: Monte-Carlo Simulation

a = -0.5

Result : BAL 70-90 deg.

a = -0.6


a = -0.7


a = -0.8


a = -0.9


a = -1.1


a = -1.2


a = -1.3

Result :

No edge-on BAL quasars

a = -1.4

Result :

Cannot be explained by viewing angle

Schematic picture

Result :

At least considering , edge-on BAL cannot be denied.

Small number of BAL quasars have large-scale radio sources

Study 2 : FR2 quasars survey

100kpc

rare Gregg+ 2006

Shankar+ 2008

Radio Quiet Radio Loud (not FR2)

Radio Loud(FR2)

non CVI BAL 22,893 1,782 133CVI BAL 3,540 288 10

Study 2 : FR2 quasars survey FR2 quasars at

– Constructing SDSS DR7 FR2 quasars catalog with method taken by DeVries+ 2006

– Fraction of FR2 quasars is– 0.5 ± 0.1% for non-BAL quasars– 0.3 ± 0.2% for BAL quasars

– There are not so large difference.– Do both BAL/non BAL possess the same central

engines ?

Do both BAL/non BAL possess the same central engines ?

– FR2-BAL quasars have large Blackhole mass and low Eddington ratio.

– But sample is too small (10 sources)


500pc

Hayashi, Doi & Nagai submitted

Radio-loud BAL quasars were said to be …– steeper than non-BAL quasars

It can be explained by viewing angle (DiPompeo+ 2011,2012)

– moderately radio loud Beaming effect cannot be denied (this work)

– more compact than non-BAL quasars It was observational bias (this work)

– Polar BAL (Ghosh+ 2007) ???

Summary

29

1.7–4.9GHz

Jet

Spectral index map

– スペクトル指数のコントラスト⇒ 中心エンジンの同定

– 1kpc スケールの双対ジェット

– 複数の成分から成るジェット

500pc

: Spectral index

中心エンジン

Result :

How can we identify the radio counterparts?

– Do visual inspection ? (e.g., Best+ 2005, Kimball+ 2008) – Here, we take statistical method taken by “de

Vries+ 2006”


search center

1. Extracting the radio core– 3 and 10 arcsec within each search center for FIRST and

NVSS

Method

search center

2. Searching for candidates for radio lobe– 450 and 600 arcsec within each search center for FIRST

and NVSS

Method

search center

2. Searching for candidates for radio lobe pair– Selecting a radio pair which has maximum value of

Method

search center

1 0

234

Faint Images of the Radio Sky at Twenty-Centimeters(R. H. Becker+ )– Radio imaging survey at 20 cm– Coverage : 10,635 square deg.– Resolution : ~5 arcsec– r.m.s. level : ~0.14 mJy/beam

The arrival of the FIRST VLA survey

Kimball+ 2008

VLA

Finding of radio-loud BAL quasars– FIRST Bright Quasars Survey

• Spectroscopic survey for radio selected sources.• Many moderately radio-loud BAL quasars are found.• Lack of RL-BAL in previous study was affected by selection

effect.

2000s : “pioneering age”R

adio

loud

Radio loud

cutoff

Becker+ 2000

Becker+ 2001

Nature of the radio sources– Radio-loud BAL quasars have …

• compact morphology less than a few kpc

• convex spectra peaked at 100 MHz-10 GHz

2000s : “pioneering age”

VLA image

FRII large structure is rare

(Montenegro-montes+ 2008)

Gregg+ 2006VLA image

low 　　　　highpeak frequency

smal

l　　

　　

larg

e　

　lin

ear s

ize

low 　　 frequency 　　high

smal

l　　

flux　

　la

ge 　　　 yrs1kpc 　　　

yrs100pc

　　　 yrs10kpc

～ 105-6

yrs10kpc

～ 104-

5yrs1kpc

～ 102-

3yrs100 pc

General radio nature of AGN- Compact sources suffers

from absorption at low frequency

- Spectral peak shifts toward lower frequency as sources evolve

Snellen+ 2000

2000s : “pioneering age”

Orientation scheme of BAL quasars– Large degree of polarization at BAL

deeply-absorbed direct ray and less-absorbed scattered ray

with edge-on disk wind ?

Can the edge-on model explain the fraction of BAL completely?

1990s : “dark age”

Cohen+ 1995

Finding of Polar BAL quasars– Pole-on viewed quasars shows large flux variability

due to relativistic effect.

– Significant amount of variable sources (~15) are foundvia comparison of NVSS and FIRST survey. (Zhou+2006, Ghosh+ 2007) Polar BAL quasars ?

The edge-on scheme breaks down?

2010s : “golden age”

UMRAO

(Ghosh+ 2007)

Radio spectrum and orientation of the source


3C175 NRAO

Orientation

Spe

ctra

l ind

ex

Fine+ 2011

Flux

Frequency

Flux

Frequency

NGC1052 NRAO/AUI

Edge-on 3C380 Kameno

pole-on

lobe lobe

core core

Radio spectral index depends on the orientation

Radio spectrum of BAL quasars– Multi-frequency survey for 74 radio-loud BAL quasars

with control sample.

• The orientation effect must works.• BUT the fraction cannot explain only by the orientation.


DiPompeo+ 2011, 2012

BAL quasars are more edge-on than non-BAL quasars

edge-on pole-on

radio properties of bal quasars

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