AGN as extreme frontiers of our Universe

H. Sol, LUTH, Observatoire de Paris

ASTRONET meeting, Poitiers 2007

Exploring black hole Exploring black hole magnetospheresmagnetospheres

‘‘Extreme frontiers’  open one natural question : Extreme frontiers’  open one natural question :

‘‘How is the ‘transition layer ??’How is the ‘transition layer ??’ (the no man’s land or the « black hole (the no man’s land or the « black hole

magnetosphere ») between magnetosphere ») between

- boundary conditions at the BH horizon - boundary conditions at the BH horizon (panel (panel A)A)

- and outer context of the host galaxy - and outer context of the host galaxy (panel B)(panel B)

(related to key question 2.3 on strong gravity in (related to key question 2.3 on strong gravity in action, and key question 2.5 on accretion and action, and key question 2.5 on accretion and jets)jets)

going beyond going beyond the ‘AGN the ‘AGN

paradigm’ …paradigm’ …

Central black hole (gravita-tional waves)

Accretion disk (UV, X, optical)

Dusty torus (IR, HAR, interfero)

Hot gas andclouds (X, UV,IR, optical ...)

Relativistic jet (gamma, X, radio,neutrinos, CR ...)

Host galaxy (blue) and its radio emission (orange)

multi-lambda mapping

The standard AGN cartoon

Sub-questionsSub-questions Detailed description of the different Detailed description of the different media, media, of their of their

interfaces interfaces and and interactioninteraction, direct probes of their , direct probes of their existence : disk/‘torus’/BLR/jet/windexistence : disk/‘torus’/BLR/jet/wind

Physical processesPhysical processes : various accretion regimes, jet : various accretion regimes, jet formation, magnetism, turbulence, shocks, particle formation, magnetism, turbulence, shocks, particle acceleration, radiation processes, origin and fate of acceleration, radiation processes, origin and fate of gas and dust ?...gas and dust ?...

Origine of activity ?Origine of activity ? Reservoir for AGN fuelling, Reservoir for AGN fuelling, conditions for active and quiet phases ? conditions for active and quiet phases ? (Black hole (Black hole active by accretion in AGN and blazars, or dorment active by accretion in AGN and blazars, or dorment as in our galactic center).as in our galactic center). Relative importance of the Relative importance of the Blandford-Znajek process ? Relation between activity Blandford-Znajek process ? Relation between activity and star formation ?and star formation ?

Which dominant parameters and Which dominant parameters and conditions for conditions for radio-loudnessradio-loudness and radio-quiescence ? and radio-quiescence ? (Several (Several clues for rotating BH question the validity of the spin clues for rotating BH question the validity of the spin of the central BH as dominant parameter for radio-of the central BH as dominant parameter for radio-loudness) loudness)

Unification schemesUnification schemes, test and limits of the , test and limits of the orientation scenario, role of environment, evolution, orientation scenario, role of environment, evolution, … …

ExperimentsExperiments

Very compact regions -->Very compact regions -->high and high and very high angular resolution very high angular resolution experimentsexperiments, and/or , and/or monitoringmonitoring of of variability (short time scales)variability (short time scales)

Multi-spectral (from radio to TeV Multi-spectral (from radio to TeV gamma rays) and non-photonic gamma rays) and non-photonic emittors emittors multi-wavelength and multi-wavelength and multi-messengers approachmulti-messengers approach

Remote sources Remote sources high sensitivity high sensitivity detectorsdetectors

Two types of experimentsTwo types of experiments(in addition to those listed (in addition to those listed

yesterday)yesterday) InterferometryInterferometry : : - VLBI, space VLBI VLBI, space VLBI (cf talk by A. Lobanov)(cf talk by A. Lobanov)- futurist project of space X-ray interferometer futurist project of space X-ray interferometer (cf MAXIM …)(cf MAXIM …)- large IR/optical interferometers (VLTI, OHANA large IR/optical interferometers (VLTI, OHANA

on Mauna Kea, space interferometer) on Mauna Kea, space interferometer) cf : recent interferometric observations cf : recent interferometric observations

of a of a few AGN dusty torus with MIDI at few AGN dusty torus with MIDI at VLTIVLTI

Very High Energy (VHE) ground based Very High Energy (VHE) ground based gamma-ray observatoriesgamma-ray observatories (CTA: Cherenkov (CTA: Cherenkov Telescopes Array)Telescopes Array)

--> an emerging promising field in --> an emerging promising field in Europe Europe

with recent HESS (and MAGIC) with recent HESS (and MAGIC) discoveriesdiscoveries

Background : Background : Opening of the TeV window Opening of the TeV window

Number of known TeV cosmic sources

0

5

10

15

20

25

30

35

40

TeV sources unconfirmed sources

A significant sample of TeVsources; differenttypes of sources

New eyes on theVHE gamma ray sky revealed the richness of the cosmosat TeVenergies.

The radiogalaxy The radiogalaxy M87 : a new type of M87 : a new type of

TeV AGNTeV AGN

Confirmation of the TeV detectionof M 87 by HESS

Short time scale variability impliesan emitting zone with size of a few Schwarschild radius (Dec 2006). Similar results on other AGN.

TeV observations explore the immediate BH surroundings.

Constraint on LIR results in a constraint on the accretion regime.

Strong constraints on particleacceleration processes

Modelling of spectral energy Modelling of spectral energy distribution distribution

ex : PKS 2155-304 ex : PKS 2155-304 Past sPast simultaneous data in imultaneous data in

radio, optical, X -rays and radio, optical, X -rays and γ γ -rays -rays

Both leptonic and hadronic scenarios can still reproduce the spectra : importance of a larger spectral band

The galactic The galactic centercenter

2 strong TeV sources : . J1745-290 (Sgr A* ?). G0.9+0.1200 pc, resolution < 6’

Mapping of diffuse TeVemissionafter subtracting two pointsources. Correlation withmolecular component (CS)(Nature, 2006)

The TeV flux requires a cosmic rays energy density > 3 times the one in sun environnement, and a harder spectrum : suggests recent acceleration of CR, < 10 000 years, near the G.C. (SNs or active BH) --> Detailed mapping of diffuse emission could inform on the temporal evolution of activity of the central BH …

Next generation of CherenkovTelescopes (CTA)

from G. Hermann, Nov 2006

expected sensibility

Perspectives of statistical studies of TeV AGNPerspectives of statistical studies of TeV AGN Different tests of AGN unifying schemes and classification by Different tests of AGN unifying schemes and classification by

orientation; provide typical intrinsic TeV AGN spectra. orientation; provide typical intrinsic TeV AGN spectra. Develop the new VHE physics and modelling of BH Develop the new VHE physics and modelling of BH

magnetospheres magnetospheres With an AGN sample at different z, explore the gamma-ray With an AGN sample at different z, explore the gamma-ray

horizon of our universe Very horizon of our universe Very (high z TeV blazars useful to (high z TeV blazars useful to constrain the IR extragalactic background, which partially absorb constrain the IR extragalactic background, which partially absorb the VHE the VHE γγ photons by pair creation : photons by pair creation : γγVHEVHE ++ γ γIR IR ee+ + ee-)-)

Cosmological issues on the extragalactic background light Cosmological issues on the extragalactic background light (EBL)(EBL)

Exploring the universe with VHE detectorsExploring the universe with VHE detectors Search for new types of cosmic sources, ‘dark’ acceleratorsSearch for new types of cosmic sources, ‘dark’ accelerators Look for TeV signature of primordial black holes ?Look for TeV signature of primordial black holes ? Simultaneously, look for possible minor constituents of dark Simultaneously, look for possible minor constituents of dark

matter : cosmic strings (possible gamma sources), remnants of matter : cosmic strings (possible gamma sources), remnants of topological defects from primordial phase transition, ‘isolated’ BH topological defects from primordial phase transition, ‘isolated’ BH expelled from host star clusters, unidentified TeV sources expelled from host star clusters, unidentified TeV sources

a kind of guess but given our ignorance on VHE universe and a kind of guess but given our ignorance on VHE universe and surprises we already got, this may be an important area for CTA. surprises we already got, this may be an important area for CTA. Seeing the hidden universe with VHE gamma rays …Seeing the hidden universe with VHE gamma rays …

Synergy of CTA with other Synergy of CTA with other ground and space projectsground and space projects

High mutual interest : getting a High mutual interest : getting a multi-spectral viewmulti-spectral view of cosmic of cosmic sourcessources

## CTA may provide the best chance to CTA may provide the best chance to identify non-photonic identify non-photonic sourcessources (from cosmic rays, neutrinos or gravitational waves (from cosmic rays, neutrinos or gravitational waves experiments)experiments)

Ex : LISA event rate from 1 coalescence event every five years to Ex : LISA event rate from 1 coalescence event every five years to hundreds of events per year hundreds of events per year obvious ToO for CTA obvious ToO for CTA

Often said that BH merger does not emit elmg radiation … but Often said that BH merger does not emit elmg radiation … but this sounds strange given the complexity of the BH this sounds strange given the complexity of the BH surroundings. Such event should affect activity and particle surroundings. Such event should affect activity and particle acceleration. --> acceleration. --> Detect TeV counterpart to identify the host Detect TeV counterpart to identify the host source by CTA, then multi-lambda studies to get its z source by CTA, then multi-lambda studies to get its z (in (in principle, LISA data could provide by themselves the distance principle, LISA data could provide by themselves the distance but pb of major distorsion from random gravitational lensing)but pb of major distorsion from random gravitational lensing)

## Conversely high sensitivity multi-lambda detectors may find Conversely high sensitivity multi-lambda detectors may find counterparts to counterparts to ‘dark accelerators’‘dark accelerators’ seen at TeV range (new seen at TeV range (new physics)physics)

CTA Physics Group meeting,Utrecht, November 2006