Presentation on theme: "Angela Bongiorno Max Planck Institut fuer Extraterrestrische Physik (MPE) Collaborators: Marco Mignoli (INAF-Osservatorio Astronomico di Bologna) Gianni."— Presentation transcript:
Angela Bongiorno Max Planck Institut fuer Extraterrestrische Physik (MPE) Collaborators: Marco Mignoli (INAF-Osservatorio Astronomico di Bologna) Gianni Zamorani (INAF-Osservatorio Astronomico di Bologna) and the COSMOS AGN working group AGN8 Torino May Optically Selected Type-2 AGN from the 10k zCOSMOS sample the 10k zCOSMOS sample
PI N. Scoville
The z-COSMOS project 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 I AB <22.5 (BRIGHT SAMPLE) ~10,000 galaxies at 1.4 < z <2.5 with B AB <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 spectra
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 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 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) Spectra of Active Galactic Nuclei Similar to normal star forming galaxies!! Difficult to classify just looking at the spectrum easy to classify through the broad emission lines!!
Optically selected Type-2 AGN Type-2 AGN SELECTION: 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. 4 At 0.15
Red Diagnostic Diagrams ([NII], [SII], [OIII], Ha, Hb ): 0.15
BLUE Diagnostic DiagramS: ( [OII], [OIII], Hb) : 0.5
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< of them are optically classified as SFG or SFG candidates. They constitute the 1% (34/3209) of the SFG sample. Comparison with X-RAY Selected Sample (XMM):
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.
Position of X-ray sources in the blue Diagnostic Diagram a)Emission line dominated by extremely powerful starburst galaxy (but Lx>10 43 for most of them) b)Composite Starburst - AGN (Stasinska et al. 2007) Red and blue lines: Increasing AGN contribution to the stellar locus. The difference between blue and red is in the ionization parameter. X-ray sources seem to lie in a different region of the plane !!!
Extinction? NeV (AGN) Composite spectra SFG identified in the XMM catalog SFG not identified in the XMM catalog
TYPE-2 AGN FINAL SAMPLE TOT= 258 type < z < 0.95 Sey2 : 81 Sey2 cand: 55 LINER: 122
B-band Luminosity Function: Comparison with other surveys Local Samples (for comparison): Palomar Sey sample (45 -- z~0 CfA Sey-2 sample z~0 SDSS best fit LF for z<0.13 : V max estimator M: ( m obs, for each object, is chosen in the band which is sampling the rest-wavelength closer to the B-band) Weight
SED: AGN contribution to the continuum (in the observed wavelength range) AGN=16%, E(B-V)=0.04 AGN 52%, E(B-V)=0.53 PURE GALAXIES
SED: AGN contribution to the continuum (in the observed wavelength range) 4% Early type Disk Irregular 4% 71% 25% No dependence on z and/or magnitude Statistic on galaxies that host AGN AGN contribution to the SED Most AGN are hosted in disk galaxies
Summary Work in progress and still To DO a) 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 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