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Initial Results from the Chandra Shallow X-ray Survey in the NDWFS in Boötes

Initial Results from the Chandra Shallow X-ray Survey in the NDWFS in Boötes. S. Murray, C. Jones, W. Forman, A. Kenter, A. Vikhlinin, P. Green, D. Fabricant, G. Fazio - CfA B. Jannuzi, A. Dey, J. Najita, M. Brown, K. Brand - NOAO J. Shields, B. McNamara - OhioU M. Rieke - AzU

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Initial Results from the Chandra Shallow X-ray Survey in the NDWFS in Boötes

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  1. Initial Results from the Chandra Shallow X-ray Survey in the NDWFS in Boötes S. Murray, C. Jones, W. Forman, A. Kenter, A. Vikhlinin, P. Green, D. Fabricant, G. Fazio - CfA B. Jannuzi, A. Dey, J. Najita, M. Brown, K. Brand - NOAO J. Shields, B. McNamara - OhioU M. Rieke - AzU C. Kochanek - OSU

  2. Survey Characteristics • Large contiguous area (9.3 deg2), with arc second resolution • Well studied optically - NOAO Deep Wide File Survey (NDWFS) • Accessible for spectroscopic follow up (MMT-Hectospec, Gemini, Keck, …) • Multiwavelength coverage (SST-IRAC, VLA-FIRST, GALEX, …) • Centered at =14h 32m =34 06’

  3. Science Objectives • Complete Flux Limited Contiguous Survey • Optical Ids • Redshifts • Spectroscopic complete to R < (21-22) • Photometric to R < (24-26) • Large Scale Structure • Angular and Spatial Correlations • Luminosity Function • Classes • Cluster Survey

  4. Mosaic of X-ray Fields • 126 ACIS-I pointings (ACIS-S2 chip also) • 5 ksec exposure (4287 - 5120 sec) • Fields overlap by about 1 arc minute • Total of 630 ksec of Chandra time (about 2 orbits) • March/April 2003

  5. Representative Single Field • Seq 3602 (N-F57) • Total counts ~3000 • Smoothed with 2 arc second Gaussian • Raw image analyzed with wavelet detect • 31 sources (2 cts) • 1 extended source

  6. X-Ray Survey Detection Results • Analysis in 0.5-2 keV, 2-7 keV and 0.5-7 kev bands independently • CIAO Wavedetect using 1,2,4,8 x 2 scales, 2 count (5 x 10-5) threshold yields: • 4578 pt sources (0.5-7 keV) • 3352 pt sources (0.5-2 keV) • 2008 pt sources (2-7 keV) • 42 extended sources (0.5-2 keV) • 2942 pt sources (0.5-7 keV) ≥4 counts • 1636 pt sources (0.5-7 keV) with 2 and 3 counts

  7. Spurious Sources • Fully simulate 400 source free fields using archival ACIS-I background data • Scale to 126 fields: • Expect ~22 spurious for ≥ 4 counts. • Expect ~625 spurious for ≥ 2 counts.

  8. Extended Sources • Matched Filter Analysis - (Vikhlinin 1995) • 42 Sources (0.5-2 keV) • Optical follow ups indicate most are clusters • Spectroscopic redshifts are next

  9. Cosmic Variance on ACIS-I 16’x16’ FOV • 126 Fields, 4767 sources ≥ 2 counts, 0.5-7 keV • Consistent with Poisson distribution with mean 36.33 sources per field

  10. 2-Point Angular Correlation • () is the excess probability of finding a source with ± of another source (Peebles, 1980) • We estimate () according to Landy and Szalay, 1993 • Kenter et al. Poster (43.15 yesterday) for more details • Solid line is from Vikhlinin 1995 for ROSAT 140 deg2

  11. Log N - Log S • Use convolution method (Kenter and Murray 2003) to fit survey data with 2 ct threshold. Note this is differential N(S), not integral N(>S) • Results agree with previous surveys, including Chandra Deep Fields (e.g., Giaconni 2001)

  12. Source Identifications • NDWFS - 9 deg2 in Boötes(Jannuzi and Dey, 1999; Brown et al., 2003) • Bw (U and B), R, I => 26 mag • K 19 - 19.5 => mag • K partial coverage (6 deg2) • Sub arc second astrometry • Multicolor magnitudes to few hundredths • Can get estimated photometric redshifts for galaxies, need spectra for AGN • Match to X-ray sources with ≥ 4 counts (need good positions)

  13. Fraction ≥ 4 Counts Matched • Solid Curve - R • Dashed Curve - Bw • Dotted Curve - I • Dot-dashed Curve - K • 95% have at least some match within the X-ray position uncertainty

  14. X-ray Optical Matches • Typical match • Use greater of 1.5” or 3 X-ray position error • R=23.78 m, X=5.24 ct • ~50% of X ≥ 4 ct have R > 22 m match

  15. Accurate X-ray Positions • Group of possible IDs • One uniquely within 1.5 arc seconds • R=19 m, X=11.26 • Might be a group

  16. Empty Field • X = 12.76 • Rlim=25.8 • Only 5% of ≥ 4 count X-ray sources have no match => ~150, but only ~20 spurious expected • May be extremely absorbed sources

  17. Near Bright Galaxy • X = 4.18 • Bright elliptical galaxy is 10 arc seconds offset • Can mask possible faint candidate

  18. Spectroscopy • MMT Hectospect Run • 4 Nights for NDWFS • 676 X-ray selected • 208 R<19.2 • 175 19.2<R<20.0 • 293 20.0<R<22.0 • Redshifts for 509; 353 AGN, 152 Galaxy (all z<1) • 98 0.0<z<1.0 • 183 1.0<z<2.0 • 72 z>2.0

  19. Conclusions • Survey detects expected numbers of point and extended sources. • The NDWFS is a good match to the X-ray depth and identifies most of the sources. • Optical positions can be used for multi-object spectroscopy to obtain redshifts (4 nights with MMT-Hectospec in April, a good start > 676 spectra of X-ray selected objects), more in June • X-ray follow up, especially for extended sources. • When complete will provide a true 3D survey over 9.3 square degrees

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