Transcript Active Galactic Nuclei: are they important?

Active Galactic Nuclei:
are they important?
Bożena Czerny
Copernicus Astronomical Center
Warsaw
Why I started to be interested in
AGN?
•Active Galactic Nuclei are fantastic subject
for somebody who likes to apply GR
•They consist of a massive black hole
surrounded by plentiful material flowing in
and out
•This material emits radiation so we can
trace what is happening close to a black
hole
AGN schematic structure
~ Urry & Padovani 1995
Unwanted discovery
•First seen as ‘variable stars’ on the sky
(BL Lac)
•In forties a few galaxies with strong
emission lines were identified (Seyfert)
•In sixties radio galaxies were found,
some point-like radio sources also
discovered later identified as extragalactic
sources –quasars
In 1964 accreting massive black holes
scenario was proposed (Zeldovich,
Salpeter)
Impressive career of AGN
Nowadays rich zoo of quasars,
Seyfert galaxies, radio galaxies
etc. are known under common
name of Active Galactic Nuclei,
although cosmologists and some
observers still are frequently fond
of „quasar” term.
Anyway, In the last ten years the
phenomen of active galactic
nuclei – accreting massive black
holes made anormous career
from a ‘curiosity’ to a basic
subject in cosmology. How it
happened?
“They are no ornament which just
happens to be there...” A. Fabian
2009
1999 – my unsuccesful trip to
Portsmouth
A conference was there –
5th Compton symposium
„Galaxy dynamics: from
the early universe to the
present” and I presented
there a poster.
My poster later was not
accepted for the
proceedings as it did not
fit the general line of
the Proceedings.
1999 – my unsuccesful trip to
Portsmouth
•Stable and unstable states
•Unstable states here imply
limit-cycle type oscillations –
periods of increased and
decreased accretion rate
(level of activity)
•Timescales are from
thousands of years (radiation
pressure instability) to
hundreds of tousands to
milions years (ionization
instability)
The main figure from my poster
But nowadays:
Cover page from the conference: The Monster’s Fiery Breath: Feedback
in galaxies, groups, and clusters, 1-5 June 2009, Fluno Center, Madison
Wisconsin
FEEDBACK – influence of AGN onto host galaxies and their surrounding
Turning points: 1998
MBH
Magorrian et al. :
Mbh = 0.0052 Mbulge
It implies the existence
of the mechanism
regulating the common
growth of a galaxy and a
central black hole.
Nowadays mostly in Msigma relation form.
Current version of the plot:
Gultekin et al. 2009
log(MBH/Msun) = α + βlog(σ/200 km s–1) with (α, β, epsilon0) = (8.12 ± 0.08,
4.24 ± 0.41, 0.44 ± 0.06) epsilon - dispersion
Going further: BH-dark matter
halo relation
Bandara et al. 2009
data, Booth and
Schaye 2009
simulations.
Turning points: 90’ and later
•Massive central black holes are in all
galaxies
•In most galaxies the activity is low (e.g. Sgr
A* in the Milky Way) but there is no strict
border between AGN and non-active
galaxies
•Thus again BH and galaxies likely evolve
together
Turning points: 1998
Boyle and Trelevich
(1998) - the plot of the
cosmic evolution of
quasars and Star
Formation Rate (SFR).
Also Richstone et al.98
Implies that quasar
activity and star
formation proceed
together!
How is this possible?
e.g. Collin and Zahn 1999:
 Star formation in gravitationally unstable outer part of
accretion disk around a massive black hole
 Accretion of matter by those stars
 Stellar exposions as supernovae
 Outflows leading to chemical enrichment
This explains the triggering of star formation, the nature of
fast outflows (BAL phenomenon, the solar or supersolar
abundance in all quasars, and non-zero abundance
elsewhere.
Most recent version of quasarSFR coevolution plot
Zheng et al. 2009
Cosmological simulations
need AGN input
Recent simulations by
McCarthy et al. based on
OverWhelmingly Large
Simulations project.
Without (REF) and with
AGN input.
Black histogram: data
from Loubser et al. 2009
In general, the AGN feedback
is required:
•In clusters of galaxies (to stop the
efficient cooling flows)
•In groups of galaxies (to control the
group structure through regulation of
gas mass fraction)
•In individual galaxies to control the star
formation and cold gas and provide Msigma relation
How this is possible?
Radio-loud AGN – jet outflow
Radio-quiet AGN – wind outflow
seen in the spectral data as UV and
X-ray absorbers
Likely geometry from Elvis (2000)
Combined optical-radio image
of 3C219, NRAO
Present status:
•Certainly AGN evolution and galaxy
evolution are coupled
•From cosmological simulations there
are energetic requests for amount of
AGN input
•From AGN study there are some
energetic estimates of output
Exact quantitative estimates are under
discussion and the match of the two are
under debate.
Examples: energy output
VLT Measurements of SDSS J03180600 (z=1.9257)
Dunn et al. 2009
From detailed, modelling, the mass
outflow estimated as 120 Msun/year,
kinematic energy flux of 0.1 percent of
bolometric luminosity, most probably by
a factor 50 higher due to dust, and 5 per
cent is enough to explain the ICM
heating and M-sigma relation
Mathur et al. (2009), NGC 4051
Equally careful analysis of X-ray
spectrum of NGC 4051, high
Eddington ratio nearby source, shows
that the energetic output is by
4 – 5 orders of magnitude to low to
provide the requested feedback.
Additional general argument: too low
velocities, below escape velocity
Stoll et
al.
2009
More subtle effects can be at
work
Hopkins and Elvis 2009, simulation of the ISM cloud interaction with a hot AGN
wind. Even weak wind can lead to cloud dispersion and suppression of potential
starburst event.
My contribution:
Before we can formulate the global picture we should understand better the Intrinsic
time behaviour of AGN.
Active phase, triggered by external cause (major or minor merger, or even a
molecular cloud disruption) consists of several sub-stages, i.e. it is intermittent.
Observation: radio loud sources: too
many of them are always young
Czerny, Siemiginowska, Janiuk, NikielWroczyński, Stawarz 2009, data points
from Wu (2009)
My contribution:
The same trend should be seen in radio-quiet sources. We think we have
recently found a way to detect it observationally.
In a collection of 100
000 quasars from
SDSS we have found
one with strong LILs
and weak HIL., and no
NLR.
It is most likely the
early stage of a quasar
reactivation.
Hryniewicz, Czerny,
Nikołajuk,
Kuraszkiewicz 2009.
Is intermittency important?
Certainly...
... although it is not obvious in which
direction (active stages are shorter but
then they may be more
intense/efficient)
Summary – where are we?
•AGN are important
•Central black hole evolves together in a
coupled way with the host galaxy in mutual
relation
•We start to catch some global energetic
effects qualitatively
We are still very far from the detailed
knowledge of the galaxy evolution which
should include BH interaction with
multiphase galactic and intergalactic
medium
Thus we slowly approach this
stage...
Basic principles understood in XVIII century (contribution of Edmund Halley !)