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AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
A RADIO APPROACH TO BROAD ABSORPTION LINE QUASARS
Gabriele Bruni (IRA-INAF, Univ. Bologna)
K.-H. Mack (IRA-INAF) E. Salerno (IRA-INAF)
ACTIVE GALACTIC NUCLEI IX'Black holes and revelations'
Ferrara 24-27 Maggio 2010
Broad absorption towards the
blue wing of some UV emission
lines, shifted up to ~ 0.2 c
CIVSiIV
Most probably intrinsic
HiBALs, LoBALs,
FeLoBALs.How many?
~ 15 %
Al III, Mg II, Si IV, C IV
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
BAL QSOs vs “normal” QSOs
X-Rays: Emission intrinsically similar, BAL QSOs more absorbed
(Green et al. 2001, Gallagher et al. 2007)
Sub-mm, mm: No differences (Lewis et al. 2003,
Willott et al. 2003, Priddey et al. 2007)
Mid-IR: Similar properties (Gallagher et al. 2007)
Optical: BALs more reddened, more highly polarized, UV absorption
(Goodrich 1997, Krolik & Voit 1998)
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Unification scheme of AGN
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Explanations for the BAL phenomenon
Elvis (2000)
Orientation Scenario:
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Explanations for the BAL phenomenon
Orientation Scenario:
PRO:
Naturally explains why BAL/non-BAL QSOs are so similar
Explains higher reddening/obscuration in BAL QSOs
CONTRA:
Explains higher polarisation (optical band) via resonant scattering
Variety of radio spectral indices
(Becker et al. 2000, Montenegro-Montes et al. 2008) Found both edge-on (FR II) and polar (strongly beamed)
BAL QSOs (e.g., Gregg et al. 2006, Zhou et al. 2006)
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Young or recently refueled
quasars
Explanations for the BAL phenomenon
Evolutionary Scenario:
PRO:
Anticorrelation between radio-loudness and the BAL phenomenon
(Gregg et al. 2006) Radio BAL QSOs are compact sources “like” CSS/GPS
(Montenegro-Montes et al. 2008)
CONTRA:
Same cold and warm dust properties of BAL/non-BAL QSOs(Becker et al. 2000 - Gregg et al. 2000, 2006 -
Kunert-Bajraszewska & Marecki, 2007 – Willott et al. 2004)
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Cross-over model
(Punsly, 1999)
Explanations for the BAL phenomenon
Inner jet
BAL cloud
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Explanations for the BAL phenomenon
Cross-over model:
PRO:
Naturally explains why BAL/non-BAL QSOs are so similar
Explains higher reddening/obscuration in BAL QSOs
Explain the anticorrelation between radio-loudness and the
BAL phenomenon (Gregg et al. 2006)
CONTRA:
Same cold and warm dust properties of BAL/non-BAL QSOs(Becker et al. 2000 - Gregg et al. 2000, 2006 -
Kunert-Bajraszewska & Marecki, 2007 – Willott et al. 2004)
Radio emission is an additional investigation tool!
Radio Loud BAL Quasar
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Variability study
Radio flux density variability can be used to constrain jet orientation since it can be interpreted as a sign of beaming jets oriented within a few degrees from the line of sight.
No significant flux density variation occurred in these
sources on time scales of at least 4 years
(E. Salerno et al. in preparation)
The sample was observed at several frequencies between 1.4 and 22 GHz
Measurements of the flux densities were repeatedly performed between 2005 and 2009.
Collected values were also compared with data available from literature.
New sample of 31 RL BALs + 31 comparison QSOs
(S1.4
>30 mJy)
Radio continuum & polarisation (Effelsberg, IRAM, JCMT, VLA,
WSRT, GMRT)Morphology & orientation (EVN, VLBA, global VLBI)
polarisation: particle density & magnetic fields (Effelsberg, VLA)
H I absorption & CO lines: gas component in the central engine
environment (GMRT, WSRT, IRAM)
Optical band: 36 nights at La Palma observatories in 2008.
Ionization parameters and distance of the BAL region from
the center (data still to be reduced...)
Which is the right model?
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Radio continuum & polarisation
Effelsberg 100-m dish
Very Large Array
Observations during 2007, 2008, 2009
Polarisation and continuum at 2.6, 4.8, 8.3, 10.4 GHz
31 RL BALs + 31 comparison QSOs
Observations performed in July 2009 (~40 hours)
Polarisation and continuum at 1.38, 4.8, 8.4, 22, 43 GHz
31 RL BALs + 31 comparison QSOs
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
GMRT
Observations in January 2010
Continuum at 244 & 610 MHz
6 brightest BALs of the sample
Radio continuum & polarisation
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Data reduction and analysis
Fit of the spectra with an analytical function (Orienti et al. 2009)
Determination of the peak frequency
Evidence of low frequency components
Both for comparison and BAL sample
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Results
Spectral characteristics
Peak frequency of the synchrotron emission
Spectral index
50% GPS, 50% low frequency
⅓ flat, ⅔ steep
BALs ?
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Results
Polarimetry
Polarisation percentage
Rotation Measure
Bruni et al. (in prep.)
~ 1-10% Similar to comparison
Values similar to comparison
BALs Comparisons
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
Conclusions
BALs are all unresolved @ 43 GHz (VLA - C config.): Linear Size < 8 Kpc
No particular orientation, only steep-spectrum majority
Both GPS and low frequency peaked, old components in some cases
Not extremely young radio jet
No variability
The most probable model is the Elvis one (but it must account for both steep and flat sources)
Outflow must be present only in a short phase (15% of QSOs are BALs)
AGN9, Ferrara 24-27 Maggio 2010Gabriele Bruni – IRA INAF, Univ. Bologna
...Thank you!