agn9, ferrara 24-27 maggio 2010 gabriele bruni – ira inaf, univ. bologna a radio approach to broad...

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


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)


Unification scheme of AGN


Explanations for the BAL phenomenon

Elvis (2000)

Orientation Scenario:



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)


Young or recently refueled

quasars


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)


Cross-over model

(Punsly, 1999)


Inner jet

BAL cloud



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



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?


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


GMRT

Observations in January 2010

Continuum at 244 & 610 MHz

6 brightest BALs of the sample

Radio continuum & polarisation


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


Results

Spectral characteristics

Peak frequency of the synchrotron emission

Spectral index

50% GPS, 50% low frequency

⅓ flat, ⅔ steep

BALs ?


Results

Polarimetry

Polarisation percentage

Rotation Measure

Bruni et al. (in prep.)

~ 1-10% Similar to comparison

Values similar to comparison

BALs Comparisons


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)


...Thank you!

agn9, ferrara 24-27 maggio 2010 gabriele bruni – ira inaf, univ. bologna a radio approach to broad...

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