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) Introduction 1 : ⇒ thermalaccretion disk wind is absorber? Proga+ 2000 Disk wind disk CIV Gregg+ 2000
Galaxy evolution and BAL quasars • The disk wind could suppress star formation • BAL works as AGN feedback in the course of galaxy evolution? Introduction 1 : Ellliptical Pure disk galaxy BAL Correlation between BH mass and bulge mass Classical bulge No correlation between BH and bulge mass BAL works as AGN feedback to the galaxy ?? Pseudo-bulge (Kormendy+ 2011) Quasar phase Major merger Starburst, buried quasar ? Hopkins+
Current issue: which is dominant ? • Difference of the viewing angle • Difference of the central engine Introduction 1 : BAL fraction suggests covering factor disk wind： v～0.1c BAL fraction suggests time possessing the wind disk wind： v～0.1c
Radio studies for BAL quasars is meaningful !! • The state of the disk can be obtained through radio jet Do BALquasarsand non-BAL quasars have a same central engine?? • Viewing angle to the sources can be determined • Morphology • Spectral index Introduction 2 : pole-on NGC1052 NRAO/AUI Osuga+ 2011 Edge-on 3C380Kameno+
Radio spectrum and orientation of the source Introduction 2 : Fine+ 2011 3C175NRAO Spectral index pole-on NGC1052 NRAO/AUI Orientation Edge-on 3C380Kameno Radio spectral index depends on the orientation Flux Flux lobe lobe core core Frequency Frequency
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 : • What does the distribution indicate ? • difference of • the central engine ? • or • the viewing angle ? Shankar+ 2008 DiPompeo+ 2011 cutoff steep flat/inverted
Radio Spectral Index of BAL quasars Spectral index can be explained by viewing 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
Luminosity distribution • Assuming Spectral index at 1.4-5 GHz, obtained by DiPompeo+ 2011 • Reducing 5-GHz Luminosity Statistical Study : Sample DiPompeo+ 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 Result : BAL 70-90 deg.
a = -0.7 Result : BAL 70-90 deg.
a = -0.8 Result : BAL 70-90 deg.
a = -0.9 Result : BAL 70-90 deg.
a = -1.1 Result : BAL 70-90 deg.
a = -1.2 Result : BAL 85-90 deg.
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 rare Gregg+ 2006 100kpc Shankar+ 2008
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 Hayashi, Doi& Nagai submitted 500pc
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
Spectral indexmap • 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 Result : : Spectral index 1.7–4.9GHz 中心エンジン Jet 500pc
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 10arcsec within each search center for FIRST and NVSS Method search center
2. Searching for candidates for radio lobe • 450 and 600arcsec 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 2 4 3 0 1
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 VLA Kimball+ 2008
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” Radio 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” (Montenegro-montes+ 2008) FRII large structure is rare VLAimage Gregg+ 2006 VLAimage
General radio nature of AGN • Compact sources suffers from absorption at low frequency • Spectral peak shifts toward lower frequency as sources evolve 2000s : “pioneering age” smallfluxlage yrs 1kpc yrs 10kpc ～102-3yrs 100 pc ～104-5yrs 1kpc Snellen+ 2000 yrs 100pc smalllarge linear size ～105-6 yrs 10kpc lowfrequency high low high peak frequency
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 found via 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” Fine+ 2011 3C175NRAO Spectral index pole-on NGC1052 NRAO/AUI Orientation Edge-on 3C380Kameno Radio spectral index depends on the orientation Flux Flux lobe lobe core core Frequency Frequency
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