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The NuSTAR Extragalactic Survey: A 1 st Look at the Distant High-Energy X-ray Background

The NuSTAR Extragalactic Survey: A 1 st Look at the Distant High-Energy X-ray Background. D.R. Ballantyne (Georgia Tech) on behalf of

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The NuSTAR Extragalactic Survey: A 1 st Look at the Distant High-Energy X-ray Background

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  1. The NuSTAR Extragalactic Survey: A 1st Look at the Distant High-Energy X-ray Background D.R. Ballantyne (Georgia Tech) on behalf of M. Ajello, D. Alexander, R. Assef, M. Balokovic, F. Bauer, S. Boggs, K. Boydstun, C. Bridge, F. Christensen, W. Craig, G. Lansbury, A. Del Moro, P. Eisenhardt, A. Gonzalez, C. Hailey, F. Harrison, T.-N. Lu, D. Stern, W. Zhang and the rest of the NuSTAR Extragalactic Surveys Working Group

  2. The X-ray Background: Current Status NuSTAR ~100% directly resolved at <6 keV and >50% at 6-10 keV by Chandra & XMM~1-2% directly resolved at 20-30 keV peak by Swift-BAT/INTEGRAL etc • Goals for NuSTAR • Composition of ~20-30 keV peak and resolving >30-50% of the X-ray background from direct detections and stacking Chandra/XMM sources • Trace the evolution of AGNs and obscuration with redshift (NuSTAR AGN selection almost irrespective of obscuration) • Measure to high precision the high-energy properties of local AGNs to better define the physical components and modelling of the XRB DRB, Draper, Madsen, Rigby & Treister (2011)

  3. Extragalactic surveys: three-tiered design Deep: E-CDF-S (GOODS-S) ~200 ks/pointing over 0.25 deg2 Medium: COSMOS ~25-50 ks/pointing over 1-2 deg2 Large area: serendipitous Serendipitous detections, principally 100 Swift-BAT AGNs (~16 ks each) but also other NuSTAR targets to get ~3-4 deg2 of coverage See poster 109.09 by F. Civano on 1st ECDF-S and COSMOS results

  4. Serendipitous Survey Produced by: G. Lansbury, D. Alexander, A. Del Moro, J. Mullaney NuSTAR 3-24 keV image of 3C382 field Current statistics: 33 serendipitous sources detected by NuSTAR in 64 fields - 20 have been spectroscopically identified to date (including one known Galactic CV) 3C382 Multi-wavelength properties of 3C382 serendipitous source Serendipitous detection NuSTAR B NuSTAR A XMM-Newton Optical 3.4um WISE 12um WISE Here, I report on the properties of the first 10 AGNs discovered in the serendipitous survey (Alexander et al. in prep).

  5. First 10 serendips: optical spectra Example optical spectra: most of the serendipitous sources were not studied before and so we have been obtaining optical spectroscopic follow up. z=0.020 narrow-line AGN (hosted in a dwarf galaxy) z=1.073 broad-line AGN z=2.923 broad-line AGN z=0.891 narrow-line AGN Overall: 5 (~50%) are broad-line AGNs, 4 (~40%) are narrow-line AGNs, and 1 BL Lac

  6. First 10 serendips: basic properties NLAGN BLAGN NLAGN BLAGN • NuSTAR is ~100x more sensitive than Swift-BAT for AGN in Burlon et al. (2011): • average redshift is z~0.8 (z~0.03 for Swift-BAT) • average X-ray luminosity is ~3x1044 erg/s (~3x1043 erg/s for Swift-BAT) X-ray band ratios suggest that AGNs are Compton thin with NH<5x1023 cm-2.

  7. First 10 serendips: X-ray spectral fitting Broad-band 0.5-30 keV spectral fitting (absorbed power law): need to use C statistics for the majority of the sources, which are faint. Swift-XRT (or Chandra/XMM-Newton) NuSTAR Results: 5 AGNs (~50%) are obscured with NH~1022-1024 cm-2 (G~1.8).Broadly consistent with the Swift-BAT results of Burlon et al. (2011) but AGNs are ~10x more luminous.Lack of Compton-thick AGNs at this early stage is consistent with the Swift-BAT sample and theoretical expectations.

  8. First 10 serendips: joint rest-frame 10-40 keV Joint spectral fitting of the rest-frame 10-40 keV data for all non-beamed sources with LX>1043 erg/s. The best-fitting spectral slope and constraint on reflection (G~1.9 and R<1.4) are consistent with local AGNs (see poster 109.02 by Ballantyne). With these results we are starting to constrain models for the evolution in the properties of the obscuring region with redshift.

  9. Summary NuSTAR (launch in 9 days!!) • All 3 NuSTAR extragalactic surveys underway • Initial results show that, as advertised, NuSTAR will efficiently detect z<~ 2 Compton-thin AGNs regardless of the obscuring column-density

  10. First 10 serendips: UV-mid-infrared SEDs Example UV-mid-IR SEDs for two sources. Model fitting performed by Roberto Assef following Assef et al. (2008) and constraints AGN and host galaxy components, including dust reddening (E(B-V)). Key result: average stellar mass of z~0.8 NuSTAR AGNs is ~1011 solar masses, as compared to ~2x1010 solar masses for z~0.03 Swift-BAT AGNs (Koss et al. 2011) – “downsizing” in the AGN population.

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