1 / 13

EXOs: Candidate AGN at z ≥ 6 and intermediate-z evolved populations

EXOs: Candidate AGN at z ≥ 6 and intermediate-z evolved populations. Anton Koekemoer (Space Telescope Science Institute) + GOODS (Alexander, Bauer, Brandt, Chary, Conselice, Cristiani, Daddi, Dickinson, Elbaz, Grogin, Mainieri, Tozzi,..)

rudolf
Download Presentation

EXOs: Candidate AGN at z ≥ 6 and intermediate-z evolved populations

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. Galaxies and Structures through Cosmic Times, Venice • EXOs: Candidate AGN at z ≥ 6 • and intermediate-z evolved populations Anton Koekemoer (Space Telescope Science Institute) + GOODS (Alexander, Bauer, Brandt, Chary, Conselice, Cristiani, Daddi, Dickinson, Elbaz, Grogin, Mainieri, Tozzi,..) + COSMOS-XMM (Brusa, Comastri, Elvis, Finoguenov, Fiore, Gilli, Hasinger, Impey, Mainieri, Salvato, ..)

  2. Galaxies and Structures through Cosmic Times, Venice AGN log FX (erg s-1cm-2) FOpt (mag) • Large X-ray/optical/IR surveys are opening up new regions of parameter space: • Depth probes faint end of AGN LF to high z • Area probes high end of AGN LF at high z • Combined optical + X-ray depth allows wider exploration of FX/FOpt and new populations • Relevant surveys: • GOODS/CDFN+S (15’) • E-CDFS (30’) • XMM-LH (30’) • EGS (10’x 60’) • COSMOS (1.4o x 1.4o) • ..

  3. Galaxies and Structures through Cosmic Times, Venice FX/Fopt = 0.1 FX/Fopt = 10 u u u u u u u • FX/FOpt parameter space: • AGN typically ~1-2 dex • SB are lower Fx/Fopt • Highest FX/FOpt: • “EXO’s” - Extreme X-ray /Optical sources: • Fx/Fopt > ~100 • Only revealed byextending optical depthbelow i or z ~ 24 - 25 • Appear to have no comparable analogs in the local universe • Why do we only start seeing them at faint magnitudes? • What produces the high FX/FOpt - these sources likely consist of two sub-populations: • Balmer break: z ~ 2 - 3 evolved or dusty hosts (DRGs, EROs) • Lyman break: candidate z > 6-7 agn

  4. Galaxies and Structures through Cosmic Times, Venice • Fx/Fopt vs Colour: • Sources with low FX/FOptare generally blue: low-zstar-forming galaxies • Some blue sources alsohave FX/FOpt typical ofunobscured AGN- quasars • Moderately red galaxies(z - K > 2) all have higherFX/FOpt, obscured AGN • Reddest z - K sources: • for z - K > 4, FX/FOpt increases to ~ 10 - 100x the value for even typical obscured AGN • Not a selection effect: • high FX/FOpt should not necessarily imply bright IR flux • Thus red opt/IR colour is intrinsic characteristic of EXOs

  5. Galaxies and Structures through Cosmic Times, Venice • Previous studies of optically faint X-ray sources: • Initial Deep Chandra/XMM fields revealed that ~20-30% ofX-ray sources are “optically faint”, R > 24(Koekemoer et al. 2002, Tozzi et al. 2002) • Most optically faint sources are also X-ray faint, ie have fairly normal FX/FOpt typical of obscured AGN at z ~ 1-3 (Brusa et al. 2003, Mainieri et al. 2004, Fiore et al 2005) • Some optically faint sources are ERO’s (z ~ 1-1.5) - but also have normal FX/FOpt(Stevens et al. 2003, Yan et al. 2003, Rigby et al. 2005) • EXO’s: • Optically faint sources with anomalously high FX/FOpt >100 • No apparent local analogs at brighter magnitudes • Typically have redder z-K than ERO’s (Koekemoer et al. 2004, 2006)

  6. Galaxies and Structures through Cosmic Times, Venice • Nature of EXOs: • Need further IR constraints on SED to determine which sub-population a given EXO belongs to based on its red opt/IR: • Balmer break (z ~ 2 - 3 evolved or dusty populations) • Lyman break (z >6 AGN) • NOTE: expect EXOs to contain both z~2-3 and z>6 sources • Spitzer data: • currently based purely on GOODS CDFS + HDFN (Dickinson) • all EXOs are detected in IRAC data: • red K - IRAC colour • across IRAC, have a mixture of SEDs (red, flat or blue) • MIPS detections/non-detections are consistent with IRAC properties: • flat/red IRAC -> MIPS detections, usually brighter than IRAC • blue IRAC colours -> generally undetected in MIPS

  7. Galaxies and Structures through Cosmic Times, Venice HST/ACSSPITZER/IRAC MIPS HST/ACSVLT/ISAACSPITZER/IRAC

  8. Galaxies and Structures through Cosmic Times, Venice

  9. Galaxies and Structures through Cosmic Times, Venice • SED fitting: • Parameters SSP + constant SFR, reddening, IMF, dust • Models: • initally used CB2003 • will also now include Maraston • Results: • Most EXOs arewell fit by: • z ~ 2 - 3 • evolved • ~1010-11 Mo • Some requirereddening AV ~1 • A few EXOs arenot well fit byz ~ 2 - 3 models

  10. Galaxies and Structures through Cosmic Times, Venice • Using EXOs to trace high-z AGN evolution: • AGN regulate galaxy growth / SFR via feedback • may trace hierarchical dark matter halos • possibly different types of accretion mechanisms: • luminous AGN may trace major mergers • lower-luminosity AGN may trace more minor interactions and accretion events (e.g.Merloni et al. 2004) • Hasinger etal. luminosity-dependent density evolution LDDE: • High-lum AGN grow earlier in universe, peak at z ~ 2 • Lower-lum AGN peak much later, z~1, decline by 10x to z=0 • Questions: • how does the faint end of the AGN LF evolve beyond z ~6? • does obscured/unobscured AGN ratio increase beyond z ~6? • does more rapid evolution of high-lum AGN trace merging history of spheroid formation?(e.g, Franceschini et al 1999)

  11. Galaxies and Structures through Cosmic Times, Venice • Using EXOs to count high-z AGN in GOODS: • Use XLF to estimate expected number of optically unidentified sources as a function of redshift • Most of the optically unidentified AGN are evolved interlopers at intermediate z > 2 • Compare with observed number of undetected sources: • use existing X-ray detection limits • apply optical detection cut-off (z(AB) ~ 27.5 for ACS) • Integrate over X-ray luminosities at each redshift bin • assume Type 1/2 ratio found in GOODS by Treister et al • Use the difference to calculate cumulative number N(>6) • Compare with N(>6) from XLF

  12. Galaxies and Structures through Cosmic Times, Venice • Predict optically unidentified sources in each redshift bin using Hasinger et al. LDDE description, extrapolating upto z ~ 7 • Apply to GOODS X-rayselection, including theoptical detection limits, tocalculate EXOs expected. • Number of optically unID’d sources N(z) based onz(AB)=27.5 limit, for currentChandra catalogs: • LDDE predicts 9 - 16 EXOs in GOODS (out of 607 X-ray sources): • 8-13 should be at z ~ 2 - 5 • 1-3 should be at z ~ 6 - 7 • Actually detect 13 EXOs: • SED modelling confirmsthat 10 are at z ~ 2 - 4 • 3 are indeterminate

  13. Galaxies and Structures through Cosmic Times, Venice • Conclusions: • Number of EXO’s found in GOODS agrees well with that expected based on LDDE (13 vs 9-16, respectively) • Number of intermediate-z interlopers among EXOs also agrees with expected from LDDE (10/13 vs 8-13/9-16) • Remaining number of 3 EXOs in GOODS with possible high redshifts (ie > 6) is consistent with the 1-3 EXOs expected at z > 6 based on extending LDDE to z ~ 6 – 7 • Therefore LDDE appears to extend up to at least z ~ 6 - 7 • This suggests that AGN growth/accretion mechanisms continue to track galaxy growth into reionization: • AGN feedback regulating star formation up to early epochs • black holes tracing dark matter halos since at least z ~ 7 • Future: • extend to COSMOS to improve LF constraints (whenever Spitzer catalogs are available for SED fitting..)

More Related