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THE EMISSION LINE RATIOS: A TOOL FOR INVESTIGATING THE PHYSICS OF THE LINE EMITTING REGIONS IN AGN Dragana Ili ć, Jelena Kovačević, Luka Popović. 1. Department of Astronomy, Faculty of Mathematics , Belgrade 2. Astronomical Observatory Belgrade. Outline. AGN properties emission line regions

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  1. THE EMISSION LINE RATIOS: A TOOL FOR INVESTIGATING THE PHYSICS OF THE LINE EMITTING REGIONS IN AGNDragana Ilić, Jelena Kovačević, Luka Popović 1. Department of Astronomy, Faculty of Mathematics, Belgrade2. Astronomical Observatory Belgrade

  2. Outline • AGN properties • emission line regions • the Broad Line Region (BLR) • physical properties • the Boltzmann plot method and the photoionization models • method to estimate the BLR physical properties 7th BSAC, Chepelare, Bulgaria

  3. Active Galactic Nuclei (AGN) • AGN phenomena – ubiquitous! • AGN properties: • compact size • great luminosities L ~ 1042 - 1048 erg/s • broad continuum (at all wavelengths) • intensive broad & narrow emission lines • variability; polarized radiation • strong radio-sources • many different types 7th BSAC, Chepelare, Bulgaria

  4. AGN – The unification model • AGN consists of: • massive black hole (107– 1010M๏) • accretion disc • emission line regions • the Broad Line Region – BLR • the Narrow Line Region – NLR • torus • jets (outflowing material) 7th BSAC, Chepelare, Bulgaria

  5. AGN – the schematic view 7th BSAC, Chepelare, Bulgaria

  6. Emission Line Spectra • Broad Emission Lines (BELs) - only permitted transitions • FWHM ~ 2000 - 10000 km/s H Hβ Hγ Mrk 817 (Ilic et al. 2006) 7th BSAC, Chepelare, Bulgaria

  7. Hβ line region • Narrow Emission Lines (NELs) - permitted & forbidden • FWHM ~ 200 - 700 km/s Optical Fe II (4400-5500 Å) emission 7th BSAC, Chepelare, Bulgaria

  8. What EL can tell us? • Kinematics of the region • velocities (line widths) • size (reverberation – time delays) • geometry (line shapes) • Physical conditions of the region • temperature • density • ionization state • - line ratios • - presence/absence of some lines 7th BSAC, Chepelare, Bulgaria

  9. Broad Line Region (BLR) • FWHM ~ up to 10,000 km/s • dimensions ~ lt-days up to lt-month • complex line shapes (large widths; double-peak lines; asymmetry) => complex and stratified region (at least 2 subregions) • geometry not known: more than one proposed model (eg. Biconical ejection, two-component model, the rotational accretion disk model...) 7th BSAC, Chepelare, Bulgaria

  10. BLR temperature Te ~ 104 K BLR density Ne ~ 1010 cm-3 The BLR physics Only estimates, not directly determined from BEL ratios! • photoionization (main heating source?) • plasma more likely closer to stellar atmospheres than photoionized nebulae (Osterbrock 1989) • There are many problems!! such as: • temperature and density estimates • problems of the Fe II emission BLR ionizingphotons There is practically no direct information on the temperature in the BLR! (Osterbrock & Ferland2006) 7th BSAC, Chepelare, Bulgaria

  11. The BLR physics Optical Fe II (4400-5500 Å) lines Many problems related to the Fe II multiplet, such as: - Photoionization models can not explain the total (UV and optical Fe II) emission - Geometrical place of Fe II emission region in AGN structure ? - etc… • photoionization (main heating source?) • plasma more likely closer to stellar atmospheres than photoionized nebulae (Osterbrock 1989) • There are many problems!! such as: • temperature and density estimates • problems of the Fe II emission BLR ionizingphotons 7th BSAC, Chepelare, Bulgaria

  12. The Boltzmann Plot (BP) • optically thin plasma, small changes in T & n(Griem 1997, Popović 2003, 2006) Ilu ≈ (hc/λ) guAul l (N0/z) exp(-Eu/kT) • for lines from one spectral series (e.g. Balmer lines) if the population of upper states (n>3) follow Boltzman distribution => excitation T Fn = (Ful λ)/(guAul) => log(Fn) = B − A·Eu Ful ≈ (hc/λ) guAull (N0/z) exp(-Eu/kT) A = log10 e/(kBT) 7th BSAC, Chepelare, Bulgaria

  13. BP method in the BLR of AGN • the BP method is applicable for approx 50% of cases (La Mura et al. 2007) • why BP works only for some AGN type 1? • If BP works in case of a BLR,  the BLR is in PLTE, so howthis can be explained with the photoionization model? Using the classical photoionization model of the BLR  under some conditions the populating of upper levels in the Balmer lines is driven by temperature  the BP method can be applied for the BLR diagnostics 7th BSAC, Chepelare, Bulgaria

  14. CLOUDY simulations (Ferland 1998) • set a minimal number of input parameters of standard BLR and vary hydrogen density (nH = 108– 1012 cm-3), ionizing flux (FH = 1017-1021) and column density (NH = 1021– 1025 cm-2) • analyze some emission line ratios generated by the code: the Balmer lines and HeII4686/ HeI5876 ratio • apply the BP method on Balmer lines and calculate the BP temperature TBP • consider the average temperature Tav of the region 7th BSAC, Chepelare, Bulgaria

  15. The error of the BP applied on the CLOUDY’s Balmer line series NH = 1023 cm-2 NH = 1024 cm-2 The parameter space where f<10%is well defined and constrained (in a similar range for different NH) 7th BSAC, Chepelare, Bulgaria

  16. the phyisical parameters of the simulations for which the BP method could be applied (f < 10%) follow some relations even when NH changes • the average temperature and the helium lines ratio R= HeII4686/ HeI5876 : Tav= A+B · R • the hydrogen density and the helium line ratio R: log nH = D/(C + R) [nH is in 107cm−3] Ilić et al. 2010, sent to MNRAS 7th BSAC, Chepelare, Bulgaria

  17. SDSS Galaxy Map • SDSS imaged 8,400 square degrees of the sky in five optical bandpasses (230 million objects) • obtained spectra of 930,000 galaxies, 120,000 quasars, and 225,000 stars 7th BSAC, Chepelare, Bulgaria

  18. SDSS sample • 90 objects, selected to have: • z < 0.4 • entire Balmer line seriescovered, and clearly recognized, at least up to Hδ • broad component detectablefor each Balmer line • measure Balmer line fluxes • applied BP method • measure HeII 4686 and HeI 5876 7th BSAC, Chepelare, Bulgaria

  19. Results for the SDSS sample • Tav=5700-18700 K • nH=108.2-1011.1 cm-3 • correlations between the BLR physical parameters (average temperature and hydrogen density) and the FWHM and FWZI of the BELs Ilić et al. 2010, sent to MNRAS 7th BSAC, Chepelare, Bulgaria

  20. The AGN sample and Fe II template (see talk of Jelena K. in the next session) • 302 AGN spectra, SDSS (DR7) • Fe II line emission analysed in details • study origin of Fe II and other properties Kovačević et al. 2010, ApJS, accepted

  21. Conclusions • for a limited space of physical parameter (nH and ΦH) the photoionization can affect the Balmer lines in such way that the BP method is working • in that case, the BP excitation temperature can be very useful for diagnostics of the BLR Te • for the same space of physical parameters, the ratio of the helium lines (He II λ4686/He I λ5876) can indicate the BLR hydrogen density 7th BSAC, Chepelare, Bulgaria

  22. Conclusions • the average temperature and hydrogen density in the BLR: Tav=5700-18700 K nH=108.2-1011.1cm-3 • we found correlations between the BLR physical properties and the geometry (FWHM and FWZI) 7th BSAC, Chepelare, Bulgaria

  23. Thank you for your attention! 7th BSAC, Chepelare, Bulgaria

  24. AI-VO, Belgrade, June 29 – July 1 • Paolo Padovani (European Southern Observatory)   • Evanthia Hatziminaoglou (European Southern Observatory)   • Milan S. Dimitrijević (Astronomical Observatory Belgrade)   • Petr Skoda (Astronomical Observatory Ondrejov, Czech Republic )   • Igor Chilingarian (Observatoire Paris-Site de Meudon, France)   • Milcho Tsvetkov (Sofia Sky Archive Data Center, BAS)   • Katja Tsvetkova (Sofia Sky Archive Data Center, BAS)   • Žarko Mijajlović (Faculty of Mathematics, Univ. Belgrade)

  25. AstroMundus • 2-years Erasmus Mundus Masters Course (120 ECTS) in Astrophysics offered by: University of Innsbruck, Padova, Rome, Goettingen and Belgrade • students carry out their master studies in at least 2 and up to 4 countries • Joint Master Degree issued by all partner universities www.astromundus.eu dilic@math.rs

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