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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 !)