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Angela Bongiorno Max Planck Institut fuer E xtraterrestrische Physik (MPE)

Optically Selected Type-2 AGN from the 10k zCOSMOS sample. Angela Bongiorno Max Planck Institut fuer E xtraterrestrische Physik (MPE). AGN8 Torino 19-22 May. Collaborators: Marco Mignoli (INAF-Osservatorio Astronomico di Bologna)

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Angela Bongiorno Max Planck Institut fuer E xtraterrestrische Physik (MPE)

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  1. Optically Selected Type-2 AGN from the 10k zCOSMOS sample Angela Bongiorno Max Planck Institut fuer Extraterrestrische Physik (MPE) AGN8 Torino 19-22 May Collaborators: Marco Mignoli (INAF-Osservatorio Astronomico di Bologna) Gianni Zamorani (INAF-Osservatorio Astronomico di Bologna) and the COSMOS AGN working group

  2. PI N. Scoville

  3. The z-COSMOS project VIMOS @VLT spectra • Redshift survey of 40,000 galaxies in the HST-COSMOS field • 600 hrs of observation with VIMOS on VLT started April 2005 • Spectra will be obtained for: • ~25,000 galaxies at 0.3 < z < 1.0 selected to have IAB<22.5 (BRIGHT SAMPLE) • ~10,000 galaxies at 1.4 < z <2.5 with BAB<25 and chosen by color-selection criteria (DEEP SAMPLE) • Extra targets from XMM, GALEX and radio catalogue • Goals: • Redshift Survey to identify and characterize environment • Accurate census of galaxy populations • Targetted AGN & X-ray sources

  4. Spectra of Active Galactic Nuclei According to the Unified Model, AGN can be classified into two categories depending on whether the central Black Hole and its associated continuum and broad emission line region are viewed directly (type-1) or are obscured by a dusty circumnuclear medium (type-2) Type-1 AGN(BLAGN): permitted atomic transitions - “broad” ~ 10 4 Km s-1 forbidden atomic transitions - “narrow” ~300 Km s-1 continuum emission --> power law spectrum easy to classify through the broad emission lines!! Type-2 AGN (NLAGN) : permitted atomic transitions - “narrow” ~ 300 Km s-1 forbidden atomic transitions - “narrow” ~ 300 Km s-1 continuum emission dominated by the stellar emission of their host galaxy Similar to normal star forming galaxies!! Difficult to classify just looking at the spectrum

  5. Optically selected Type-2 AGN Type-2 AGN SELECTION: • Selection of all the emission line galaxies • Distinction between Star forming galaxy and type-2 AGN To distinguish between type-2 AGN and SFG we used the Diagnostic Diagrams which use line ratios to determine the ionizing source responsible for the emission line spectrum. • At 0.15<z<0.45 (when we detect[NII], [SII], [OIII], H, H) we use the RED Diagnostic Diagrams (Kewley et al. (2001): [OIII]/H vs [SII]/H and [OIII]/H vs [NII]/H • At 0.5 <z<0.95(when we detect [OII], [OIII], H) we use the BLUEDiagnostic Diagram (Lamareille, F.; Contini, T.): [OIII]/H vs [OII]/H • Final quality flag on the basis of the quality of the spectra lines

  6. Red Diagnostic Diagrams ([NII], [SII], [OIII], Ha, Hb ): 0.15<z<0.45 Sey-2 region Sey-2 region LINERs region LINERs region Star forming galaxies region Star forming galaxies region The classification has been obtained using the position of each object in both diagrams. Red circles correspond to objects classified as Sey-2, yellow circles correspond to the objects classified as LINER, while green circles are objects classified as SFG.

  7. BLUE Diagnostic DiagramS: ( [OII], [OIII], Hb) : 0.5<z<0.95 Red circles: Sey-2 Green circles: SFG. Cyan circlescandidate Sey2Magenta circles: candidate SFG Sey-2 region Star forming galaxies region

  8. Comparison with X-RAY Selected Sample (XMM): • In the total sample of objects with emission lines only 52/3651 (=1.4%) • objects have an X-counterpart • 18 of them are optically classified as Sey-2, LINER or Sey-2 cand. They constitute the 7% (18/258) of the type-2 AGN sample. But they become the 21% (16/77) if we consider obj at I<21.0. • 34 of them are optically classified as SFG or SFG candidates. They constitute the 1% (34/3209) of the SFG sample.

  9. Position of X-ray sources in the Red Diagnostic Diagrams IN the RED Diagnostic Diagrams, most of the X-ray sources (crosses) occupy the Sey-2 / LINER region or at least they lie close to the AGN/SF separation.

  10. Position of X-ray sources in the blue Diagnostic Diagram Emission line dominated by extremely powerful starburst galaxy (but Lx>1043 for most of them) b) Composite Starburst - AGN (Stasinska et al. 2007) X-ray sources seem to lie in a different region of the plane !!! Red and blue lines: Increasing AGN contribution to the stellar locus. The difference between blue and red is in the ionization parameter.

  11. Composite spectra SFG identified in the XMM catalog SFG not identified in the XMM catalog NeV (AGN) Extinction?

  12. TYPE-2 AGN FINAL SAMPLE Sey2 : 81 Sey2 cand: 55 LINER: 122 TOT= 258type-2 AGN @ 0.15 < z < 0.95

  13. B-band Luminosity Function: Comparison with other surveys Weight : Vmax estimator M: ( mobs, for each object, is chosen in the band which is sampling the rest-wavelength closer to the B-band) • Local Samples (for comparison): Palomar Sey sample (45 -- type-1+type-2) @ z~0 CfA Sey-2 sample (23) @ z~0 SDSS best fit LF for Sey-2 @ z<0.13

  14. SED: AGN contribution to the continuum (in the observed wavelength range) PURE GALAXIES AGN 52%, E(B-V)=0.53 AGN=16%, E(B-V)=0.04

  15. No dependence on z and/or magnitude 4% 71% 25% 4% Early type Disk Irregular SED: AGN contribution to the continuum (in the observed wavelength range) AGN contribution to the SED Statistic on galaxies that host AGN Most AGN are hosted in disk galaxies

  16. Summary • 258 type-2 AGN optically selected from the 10k zCOSMOS sample through the emission lines ratio b) The comparison with the X-ray catalog shows that: • A significant fraction of optically selected type-2 AGN is missed from the XMM catalog because the line selection method allow us to go deeper (Chandra will add some sources). • A significant number of objects X-ray detected fall in the starforming region of the DD. A reasonable explanation is that they are composite objects (AGN/SB) and/or with a significant extinction on galaxy scale. • c) Determination of the luminosity function up to high redshift (z<0.95) d) The fraction of galaxy with active nuclei is ~5% in the whole redshift range Work in progress and still To DO 1) Study of the Spectral Energy Distribution. Decomposition of AGN and host galaxy. • Derivation of the AGN contribution to the continuum in the observed wavelength. • Host galaxies type and comparison with the morphology derived from the ACS images. 2) Study of the environment (bright excess of type-2 at z<0.45) 3) OIII line luminosity function

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