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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 wind
disk
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
Flu
x
Frequency
Flu
x
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 1,874
CVI 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
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 1,782 133
CVI 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)
Study 2 : FR2 quasars survey
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”
Study 2 : FR2 quasars survey
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
2
34
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
small
larg
e
linear
size
low frequency high
small
flux
lage
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
2010s : “golden age”
3C175 NRAO
Orientation
Spe
ctra
l ind
ex
Fine+ 2011
Flu
x
Frequency
Flu
x
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.
2010s : “golden age”
DiPompeo+ 2011, 2012
BAL quasars are more edge-on than non-BAL quasars
edge-on pole-on