1 / 37

THE INNER PART OF AGN: Suzy Collin Observatoire de Paris-Meudon, France

THE INNER PART OF AGN: Suzy Collin Observatoire de Paris-Meudon, France. The inner region of AGN : a phenomenological view Some comments about the methods for studying the WA. I. THE INNER REGION OF AGN. 1. The accretion disk. What we know:

cato
Download Presentation

THE INNER PART OF AGN: Suzy Collin Observatoire de Paris-Meudon, France

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE INNER PART OF AGN: Suzy Collin Observatoire de Paris-Meudon, France The inner region of AGN : a phenomenological view Some comments about the methods for studying the WA

  2. I. THE INNER REGION OF AGN

  3. 1. The accretion disk What we know: radiative coupling between a cold and a hot medium What we do not know: hot spherical corona, or (patchy) corona sandwiching the cold disk? turbulent viscosity in the cold disk and non-local magnetic heating of the corona? limits of the hot corona? etc….

  4. 2. The BLR What we know: - Photoionized medium with ionization parameter ( =L/nR2) 1 (depends on the spectral distribution and the limits) - Density 109-1012cm-3, - CD: 1022-1024 cm-2, - Coverage factor > 0.1, - Distance 103-105Rg, ionization stratification, - Velocities close to Virial, - Small micro-turbulent velocities.

  5. What we do not know: - What is the dynamics of the BLR (probably dominated by rotation for LILs + outflows for HILs) - What is the structure of the BLR? Is it continuous or clumpy? - What is the origin of the BLR? Thermal instabilities in a hot dilute medium, bloated stars, accretion disk, wind… - Are the BLR clouds confined (gas, magnetic pressure…) or transient? - What governs the size of the BLR? Wind corona, dust sublimation, or simply LOC model…? - What controls the low and high cut-off of the velocity? - What is the explanation of some very high FeII intensities? Etc…

  6. A paradox concerning the BLR There is no absorption counterpart to the BLR (cf. later) But the BLR must absorb at least 10% of the ionizing radiation, so it must have a covering factor of the central source > 0.1, and we should see BLR clouds in absorption, unless… The BLR is not located on the line of sight of the central source The lines must be produced in the same plane as the disk or just above it The disk must be either warped, or inflated (illumination by back scattered radiation is unlikely)

  7. 3. The NLR What we know: Density 104-106cm-3, CD: 1020-1022 cm-2 , coverage factor < 0.01, very small filling factor,distance 106-108Rg, Virial (or larger) velocities, small micro-turbulent velocities, conic structure What we do not know: - What is the origin of the NLR? - Is it outflowing? - Is the velocity dispersion of NLs equal to that of the bulge? (No..) - How to explain the anti-correlation of [OIII] with FeII/Hand with L/Ledd)?… AND: WHY IS THERE NO EMISSION BETWEEN THE BLR AND THE NLR (except a small ILR)?

  8. 4. The Warm Absorber What we know: • - Photoionized region; with an Ionization parameter  = 10-1000 • - Several components in pressure equilibrium • - Covering factor (by statistics and by emission lines)~0.5; • Column density Nh= 1021- 23 cm-2 (by photoinization modelling); • Outflow velocity 500-1000km/s (much larger in some NLS1s); What we do not know: - Density (by He-like emission lines, coronal lines, and variability): not well constrained; - Distance: (from density and variability): not well constrained - Clumpiness: probably small filling factor, but under discussion - As a result: we do not know Mout, neither Lkin of the flow

  9.  reverberation mapped objects A clumpy flow with a small filling factor is compatible with a modest Mout (generally smaller than Macc), and with the momentum due to radiation pressure (cf.Blustin et al. 2004). The WA is thus located close to the NLR (except in PGs)

  10. IMPOSSIBLE! On the contrary, a continuous flow should be made of “sheets”, with a large surface (to account for emission lines) and a very small thickness

  11. At these distances, the density is very small Clumpy model, with momentum due to radiation pressure

  12. A way to constrain the density: OPTICAL AND IR CORONAL LINES (Porquet, Dumont, Collin, Mouchet 1999) OVII edge OVIII edge formed in a photoionized medium with same properties as the WA

  13. An example of results (with Laor et al continuum, and average OVII and OVIII edges, average EW of coronal lines n=108 n=1012 The models favor high densities to avoid too large EW of the coronal lines. But the computations were made with an isotropic and not radial primary which overestimates emission/absorption, and not enough lines: a work to be done again with better data and a better code!

  14. SO, AS A CONCLUSION ON THE WA: The biggest unknown is the distance to the central source and the density, therefore the amount of outflowing mass

  15. 5. The UV absorption lines (NALs) What we know - Photoionized region; - Covering factor (by statistics and by emission lines)~0.5; - Column density Nh= 1018 - 21.5 cm-2 (by photionization modelling); - Density (by fine structure lines and variability): not well constrained, but probably small - Outflow velocity up to 2000km/s (much larger in BALs of course) What we do not know: - Is it the a dilute medium in equilibrium with the NLR (Crenshaw 2005) or with the BLR (Elvis 2002)? Or with nothing? - Is it a less ionized part of the WA flow (Mathur et al. 1994 and subsequent works)? Certainly, at least in some objects

  16. 6. The torus warm dust, but is it really a torus? (a warped disk is also possible) We have to wait for the results of the VLTI observations of NGC 1068…

  17. Narrow Lines Warm Absorber? UV-NALs? BALs? 6 Galactic bar Galactic bar ? ? ? THE DIFFERENT COMPONENTS (without the jet)

  18. WHERE ARE THESE COMPONENTS LOCATED? WHAT ARE THE INTER-RELATIONS BETWEEN THEM? Elvis model (2000-2004)

  19. Interesting empirical model in many respects BUT GRAND UNIFICATION IS NOT LIKELY FOR AGN (and I do not believe in Ocam’s razor for complex objects) The structure depends indeed on other parameters than the inclination: the Mass, the Accretion rate (or the Eddington factor), the environnement (a starburst for instance), etc…

  20. Examples of the influence of other parameters 1. Dominance of self-gravity of the disk Collin et al. in prep. Collin & Huré 2001 For Q=1, R=Rcrit For R > Rcrit (~5Rsg), the disk is gravitationally unstable Reverberation mapped objects: In large L/Ledd objects, the BLR is in the gravitationally unstable region

  21. Some consequences of gravitational instability 1. The disk is cut: it is broken into clumps 2. Possible extra (non-radiative) heating (FeII?); the system is inflated 3. The disk becomes strongly self-gravitating, so star formation, but the disk will disappear (Shlosman & Begelman 1989) 4. The disk stays marginally unstable, then formation and rapid growth of massive stars and explosions of SN leading to strong enriched winds (Collin & Zahn 1999) 5. High turbulence helps the accretion process

  22. 2. Launch of a wind A radiatively accelerated wind depends on M(BH) and OX (Proga & Kalmann 2004) “Toy model “of K. Leighly, 2004 It fits well the “failed wind “ of D. Proga (2005), the Murray & Chiang “hitch hicker” model, and the opt-X observations

  23. II. SOME COMMENTS ON METHODS FOR STUDYING THE WA

  24. How is modelled the WA? (a naive vision) The first step: extracting the data: the continuum, the line EWs, the RRC, Vout…

  25. The curve of growth method is sometimes used to determine the turbulence and the ionic abundances. It is imprecise, unless there are several lines from the same lower level of the same ion, with different oscillator strengths, and lines not saturated (i.e. in the Doppler part of the COG) A good case For larger column densities (>1018cm-2) and smaller Vturb it is not possible to determine both quantities precisely OVIIIseries EW/ Vturbln( ) It gives Vturb EW/  It gives Ni Crenshow et al. 2003, from Kaastra et al. 2002

  26. coverage factor ~1 coverage factor < 1 Primary source Outward emission Outward emission Complete Absorption Partial Absorption reflection There are three spectral components of the WA. The emission is generally important and should be taken into account. If the medium is outflowing, the emission lines are less blueshifted than the absorption lines. The reflection lines are mainly redshifted. It is difficult to disantangle these components. The WA can also cover the BLR emission.

  27. final profile absorption emission A typical P Cygni profile of La(OVIII) obtained for a unique shell with absorption and emission from a cone of 50° (no reflection): emission and absorption are intimately mixed.

  28. The emission contribution is different for different lines Forbidden lines appear only in emission and their ratio depends on the column density, the temperature and the density (cf. Coupé et al 2003)

  29. The emission changes the temperature deduced from the RRC Emission and absorption do not respond similarly to a change of Vturb

  30. The second step: photoionization modelling Basic underlying assumptions: stationarity (not valid if the density is small) only radiative heating (although possibility of additional modes of energy release) generally motionless, without dynamical effects (not necessarily valid for a wind) generally constant density (not necessarily valid, pressure equilibrium may be more appropriate, cf. A. Rozanska and A. Concalves talks) Many parameters: ionization parameter, column density, spectral distribution of the incident continuum (most important), abundances, micro-turbulence, density, geometry of the medium, clumpiness, coverage factor of the source… PROBABLY NOT A UNIQUE SOLUTION!

  31. Presently three photoionization codes for the WA: XSTAR (Kallmann), ION (Netzer), Cloudy (Ferland) Now: also Titan (A-M Dumont) transfer treatment: Titan is better: it has real transfer for lines and continuum (ALI cf. L.Chevallier) other codes: use escape probabilities for transfer of lines and for recombination continua but a strong dranwback of Titan: large running time, because many layers are necessary (at least 500), to get a correct line transfer for thick lines 2. Atomic data: Titan is worse: only 1000 lines are treated (XSTAR: 19000)

  32. A quick look on the escape probabilities (EP) EP (first level, used in these codes): decoupling the statistical equations of the levels from the transfer Equation, by identifying the “NRB”: with the probability of the photon to escape in a single flight from the medium: for instance for a Voigt profile with CRD (Collin et al. 1981): the probability to escape from both sides is taken into account A fraction of line photons is absorbed on the spot in the continuum (different approximations are used) The escaping line photons are treated as continuum photons

  33. So, in each layer, line photons which do not escape are used on the spot to ionize and heat the medium (i.e. homogeneously in the given layer). Those which escape are treated as continuous photons out of the layer, whose thickness is not related to the given line. So the LOCAL treatment is approximate with respect to the REABSORPTION OF THE LINE PHOTON IN THE CONTINUUM. Moreover the EP are computed with GLOBAL quantities (o) which are used in a LOCAL treatment. This is inappropriate for an INHOMOGENEOUS MEDIUM. Why is the use of the EP worse in X-ray emitting media than in the BLR? Because more lines are superposed on an optically thick underlying continuum, and the media are more inhomogeneous (T from 107 to 104 K). Note that some EP methods are as sophisticated as real transfer but they are not less time consuming (cf. Elitzur 2005)

  34. Some results concerning line intensities in the emission spectrum of a WA (Collin, Dumont, Godet, 2004). G =(x+y+z)/w of OVII is 2.5 times too large with the EP the emission spectrum displayed for FWHM=10000km/s

  35. Finally, a last question: Is the Sobolev approximation more adapted to the WA? - It applies to situations where the gradient velocity scale is smaller than the scale of the physical properties - In the line EP, o(total) is replaced by o(RVD/V) - It is adapted for a continuous medium or a clumpy medium with a large velocity gradient and many clouds on the line of sight • It is also an “escape probability” method. It requires absolutely to take into account the line overlap (cf Chelouche & Netzer and apparently also Phoenix (cf. Casebeer’s talk) • It acts like a strong micro-turbulence If Vturb is proved to be small, I am not sure that Sobolev - or improvement of it - need to be used

  36. CONCLUSION THOUGH ALREADY BIG ACCOMPLISMENTS, THERE ARE MANY THINGS STILL TO UNDERSTAND, AND MUCH WORK TO DO!

  37. Some naive questions that I would like to ask to T. Kallman - Why is only LINE radiation pressure taken into account in the total pressure, and how is it computed? - Is es taken into account (apparently yes, but why then no absorption at some frequencies for es of the order 1)? - How is taken into account the variation of VD across the slab to compute the EP? - Is it a two-stream or a one-stream computation (apparently a two-stream, but ambiguity)? - Is the line blanketting treated and how? - Is XSTAR used as an infinitely thin layer by people who compute the thermal and ionization equilibrium in their “slab” model?

More Related