1 / 32

“false-color” 0.5-7 keV X-ray image of the Bootes field

A large population of mid-infrared selected, obscured AGN in the Bootes field. Ryan C. Hickox Harvard-Smithsonian Center for Astrophysics Extragalactic Surveys Workshop Cambridge, MA 8 November, 2006 Hickox et al. 2006, submitted to ApJ.

yasuo
Download Presentation

“false-color” 0.5-7 keV X-ray image of the Bootes field

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. A large population of mid-infrared selected, obscured AGN in the Bootes field Ryan C. Hickox Harvard-Smithsonian Center for Astrophysics Extragalactic Surveys Workshop Cambridge, MA 8 November, 2006 Hickox et al. 2006, submitted to ApJ “false-color” 0.5-7 keV X-ray image of the Bootes field

  2. Collaborators Chandra (CfA) C. Jones W. Forman S. Murray A. Kenter R. Narayan Spitzer (JPL/Caltech/CfA) P. Eisenhardt M. Brodwin V. Gorjian D. Stern M. Pahre and the IRAC Shallow Survey Team Optical spectroscopy (OSU/Arizona) K. Kochanek D. Eisenstein R. Cool and the AGES Team Optical photometry (NOAO) B. Januzzi A. DeyK. Brand M. Brown and the NDWFS Team

  3. Data from Bootes survey Optical photometry: NOAO DWFS photometry Bw,R,I,J,K (Januzzi & Dey 1999) X-ray:Chandra XBootes survey (Murray et al. 2004, Kenter et al. 2005), > 3000 X-ray sources Infrared: Spitzer IRAC Shallow Survey (Eisenhardt et al. 2004) Optical spectroscopy: AGES survey w/ MMT/Hectospec ~2000 broad line AGNs, 80 narrow-line AGNs, and ~20,000 normal galaxies. ~30,000 sources are detected in all four IRAC bands.

  4. BUT, NOT REALLY! Multiwavelength studies of AGN (Urry & Padovani 1995) (Manners 2002)

  5. Multiwavelength studies of AGN (Urry & Padovani 1995) X-rays: ~3000 in Bootes sample Optical/UV ~2000 in sample Infrared:~2000 in sample Focus on high-z objects: redshifts come from spectroscopic (AGES) or photometric (IRAC + Bw, R, I, Brodwin et al. 2006) estimators. We include objects in the sample with z>0.7 (Manners 2002)

  6. Finding obscured AGN (Urry & Padovani 1995) X-raysand infrared are especially useful for identifying OBSCURED (Type 2) AGN, which are predicted from: -> unified models (e.g. Antonucci 1993, Urry & Urry & Padovani 1995) -> merger fueling models (e.g. Hopkins et al. 2006) -> cosmic X-ray background synthesis (e.g., Setti & Woljer 1989, Treister et al. 2005, Gilli et al. 2006) Much recent work has studied obscured AGN (e.g. X-ray: Alexander et al. 2005, Mainieri et al. 2005, Treister et al. 2005, Barger et al. 2005, Ptak et al. 2005, optical: Zakamska et al. 2003, infrared: Lacy et al. 2004, Martinez-Sansigre et al. 2005, Polleta et al. 2006, Brown et al. 2006, Alonso-Herrero 2006)

  7. Infraredselection of AGN Colder dust/PAHs (Lagache et al. 2004) Dust heated by AGN (Glikman et al. 2005)

  8. Infraredselection of AGN z=0.3 IRACbands

  9. Infraredselection of AGN z=0.3

  10. Infraredselection of AGN z=0.3

  11. Infraredselection of AGN z=0.3

  12. Infraredselection of AGN z=0.3

  13. Infraredselection of AGN z=0.3

  14. Infraredselection of AGN z=0.3

  15. Infraredselection of AGN Following Stern et al. (2005) See also: e.g., Lacy et al. (2004), Eisenhardt et al. (2004), Alonso-Herrero et al. (2006)

  16. Constant UV/IR spectral shape Unobscured? IRAGN 1s ~750 objects ~ L*for z=1 ellipticals (e.g. Ilbert et al. 2006) Obscured? IRAGN 2s ~650 objects Optical/UV vs. IR luminosity Hickox et al. 2006, ApJ submitted

  17. Are IRAGN 2sobscured? We test this picture with three predictions: Test 1: X-ray properties of IRAGN 2s should be consistent with absorbed AGNs: high X-ray luminosities, absorbed spectral shapes Test 2: Obscuring dust in the IRAGN 2s should be sufficient to obscure ALL the optical/UV light Test 3: IRAGN 2s should have optical morphologies and colors similar to normal galaxies

  18. Test 1: X-ray luminosities Average X-ray fluxes from stacking analysis 2-7 keV 0.5-2 keV 1044 1044 1043 1043 For both IRAGN 1s, and IRAGN 2s, average LX~1043-1044ergs s-1, typical of Seyferts/quasars

  19. HR~-0.2 for IRAGN 2s corresponds to moderate obscuration, NH~3x1022 cm-2 HR~-0.5 for IRAGN 1s corresponds to a spectrum typical of Type 1 AGNs (photon index Γ=1.8) Test 1: X-ray spectral shapes Average X-ray fluxes from stacking analysis Hardness ratio: HR=(HB-SB)/(HB+SB) crude measure of X-ray spectrum

  20. Test 2: Obscuration by dust For a typical range of gas to dust ratios (e.g., Fall & Pei 1989), for NH=3x1022 cm-2, τUV= 2.5-40 So even for the moderate X-ray absorption, the obscuring material can be optically thick in the rest-frame UV for a reasonable dust-to-gas ratio. VLT/ESO

  21. IRAGN 1 are nuclear dominated IRAGN 2 are galaxy dominated Test 3: Optical morphologies of IRAGN

  22. IRAGN 2 colors match galaxies IRAGN 1 colors match quasar Test 3: Optical colors of IRAGN templates: elliptical, Sb, quasar

  23. Are IRAGN 2sobscured? Predictions: Test 1: X-ray properties of IRAGN 2s should be consistent with absorbed AGNs: high X-ray luminosities, absorbed spectral shapes Test 2: Obscuring dust in the IRAGN 2s should be sufficient to obscure ALL the optical/UV light Test 3: IRAGN 2s should have optical morphologies and colors typical of normal galaxies

  24. Are IRAGN 2sobscured? Predictions: Test 1: X-ray properties of IRAGN 2s should be consistent with absorbed AGNs: high X-ray luminosities, absorbed spectral shapesYES Test 2: Obscuring dust in the IRAGN 2s should be sufficient to obscure ALL the optical/UV lightYES Test 3: IRAGN 2s should have optical morphologies and colors similar to normal galaxiesYES

  25. Comparison to other obscured AGN samples

  26. unabsorbed Why so few objects? Quite extincted We have found ~650 candidate obscured AGNat 0.7<z<3. This represents one of the largest populations of luminous,obscured AGN identified to date A few important questions -> How many of these are actually AGN? How many are we missing (i.e. what are the completeness and contamination)? -> Why the bimodality in obscuration at high luminosity? -> What is the underlying number density of distant Type 2 AGN, and their ratio to Type 1 AGNs? -> What are the optical spectral properties of the IRAGN 2s? -> How does this sample overlap with the absorbed AGN from other selection techniques (Chandra Deep Fields, etc.)?

  27. Summary (a poem) Observations in a great wide field of nine whole square degrees Show us thousands upon thousands of new active galaxies We can pick them out with Chandra, or in the optical instead, But we can also use their colors in the Spitzer infrared Our technique selects a lot of broad-line AGN, that's sure But we also find a lot sources that are quite obscured The X-ray, optical and infrared all do agree: This sample has a lot of obscured objects at high z! But are many even more obscured, and missing from our total? And is the distribution in AV really bimodal? Such fascinating questions loom for us in coming days! It’s quite exciting times for all these AGN surveys

  28. Test 3: Optical colors of IRAGN

  29. Test 1: X-ray luminosities (X-ray non detected) Average X-ray fluxes from stacking analysis 1044 2-7 keV 0.5-2 keV 1043 1043 1042 1042

  30. Test 1: X-ray hardness (X-ray non detected) Average X-ray fluxes from stacking analysis

  31. Tests of photo-zs IRAGN 2s

  32. Optical spectral templates

More Related