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X-ray Bright, Optically Normal Galaxies - XBONGS Forman, Anderson, Hickox, Jones, Murray, Vikhlinin, Kenter and the Bo PowerPoint Presentation
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X-ray Bright, Optically Normal Galaxies - XBONGS Forman, Anderson, Hickox, Jones, Murray, Vikhlinin, Kenter and the Bootes Team . Bootes Survey 9.3 sq. degrees with Chandra 4632 X-ray sources 1600 optical spectra NOAO Deep Wide Field Survey AGES Optical Spectroscopic Survey

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X-ray Bright, Optically Normal Galaxies - XBONGS Forman, Anderson, Hickox, Jones, Murray, Vikhlinin, Kenterand the Bootes Team

Bootes Survey

9.3 sq. degrees with Chandra

4632 X-ray sources

1600 optical spectra

NOAO Deep Wide Field Survey

AGES Optical Spectroscopic Survey

20,000 galaxy spectra

Key to success is contiguous area and efficient spectroscopy with Hectospec

XBONGS - debated nature since Einstein Obs. (Elvis et al. 1981)

Dilution of optical AGN signature by galaxy light

Absorption

Radiatively inefficient accretion flow (little optical/UV)

the xbootes survey
The XBootes Survey
  • 126 ACIS 5 ksec pointings
  • Joint GTO (Murray) and GO (Jones) program
  • 14h 32m +34 06’
  • 4642 sources detected (>=2 cts)
    • 625 spurious
  • 3293 sources detected (>=4 cts)
    • 22 spurious
  • 42 extended sources (>=10 cts)
  • fmin= 4(8)x10-15 erg cm-2 s-1 (0.5-7 keV)
  • 98% sources 4 cts matched to NDWFS candidates (R26)

Murray et al. ApJ S 163, 2005

Kenter et al. ApJ S 163, 2005

Brand et al. ApJ, 2006

spectroscopy in bootes
Spectroscopy in Bootes
  • MMT/Hectospec fiber spectrograph
    • 300 fibers
    • 6 A resolution, 4000-8000A
  • Spectroscopy
    • Complete X-ray >4 cts and I<21.5 and galaxies I<19.5
    • 1,531 X-ray selected and ~19,000 galaxies
    • 1175 Broad Line Galaxies
    • 50 Narrow Line Galaxies
    • 258 XBONGS
      • Huge sample
      • 17% of total
      • 0 < z < 1
heterogeneous class of objects
Heterogeneous Class of Objects

From optical SED’s and morphology

  • Red Ellipticals 60
  • Blue Ellipticals 84
  • Interacting 21
  • Spirals 9
  • “AGN” 12

(Fioc &Rocca-Volmerange 1997; Francis et al. 1991)

redshift distribution
Redshift Distribution

XBONGS

Broad line AGN

Narrow line AGN

XBONGS and NL AGN same distribution

xbong magnitude distribution
XBONG Magnitude Distribution

XBONG

BL (z<1)

NL

XBONG counterparts similar to NL/BL AGN

possibly somewhat fainter than NL AGN

Argues against significant dilution of lines by underlying host galaxy for all of sample

luminosity distributions
Luminosity Distributions
  • 200 XBONGs with Lx>1042 erg/s
  • 50% with Lx>1043 erg/s
  • XBONG’s and NL AGN
    • Similar Lx
    • Similar Fx/FR
  • Argues against dilution for all of
    • sample

XBONG

BL(z<1)

NL

merged x ray spectra
Merged X-ray Spectra

Type (90% error) and no absorption

Red Ellipticals 1.12-1.32

Blue Ellipticals 1.55-1.73

“AGN” 1.83-2.25

Interacting 1.28-1.56

(confirmed by hardness ratios)

Red ellipticals - for an assumed=1.9 power law

nH ~ 0.7-1.1 x 10 22 cm-2(90% confidence)

  • Some “types” absorbed, some not absorbed
irac color color diagrams following stern et al
IRAC Color-Color Diagrams (following Stern et al.)

BL AGN

XBONGS

BL AGN

NL AGN

0.45<Z<0.60

Z<0.15

0.60<Z<0.75

0.15<Z<0.30

RedBlue

0.75<Z<1.00

0.30<Z<0.45

z<0.3 Dilution - about 30%; consistent with Georgantopoulos et al.

dilution criterion

z>0.3 XBONGS concentrated under AGN wedge

radiatively inefficient accretion flows riaf
Radiatively Inefficient Accretion Flows (RIAF)
  • At low accretion rates (Yuan & Narayan)
    • - Optically thick disk is truncated at Rtrans
    • - Interior to Rtrans flow is RIAF (radiatively inefficient; optically thin)
    • - Observed in high state galactic black holes
    • X-rays from inverse Compton in RIAF
    • Little optical or UV since no disk at small radii
    • model requires L/Ledd < 0.03
  • Test RIAF model with spheroidal sample of XBONGS
    • -Use optical luminosity as proxy for MBH (108-109 Msun)
    • - MBH yields Ledd
    • -Derive AGN LBOL from SED (Elvis et al.)
    • -For 46 XBONGS, LBOL /Ledd < 0.01
    • VIABLE MODEL - needs detailed SED’s
conclusions
Conclusions
  • Large XBONG sample
    • 258 with redshifts to 1
    • Variety of optical morphologies
  • Origin of XBONG signature
    • Some dilution at low z (small fx/fR)
    • Some absorption - esp. red ellipticals with nH~1022 cm-2
    • Many sources show little (<1022 cm-2) absorption
    • RIAF (radiatively inefficient accretion flow)
      • Spheroidal sample has low Eddington ratio (Lbol/Ledd<0.01)
    • Probably some BL Lac’s

XBONG’s are a heterogeneous class

future work
Future Work
  • Deeper & Wider
    • Chandra and XMM-Newton
    • Larger samples, better S/N
  • X-ray spectra
    • Better models applied to ensemble of spectra
  • Optical spectra for fainter sources
    • Probe to higher z
  • Detailed analysis of optical spectra
    • Derive equivalent widths and line strength limits
    • Model NL galaxies, compare to XBONGS
  • Derive SED’s for different classes to test e.g., RIAF models
  • Study local environment
    • 20,000 galaxy redshifts
    • Measure local density, compare to other AGN classes

Remarkable class

Promises new insights into accretion process

slide14

MMT Bootes survey

Optical spectroscopy: AGES survey w/ MMT/Hectospec

The first sample contains ~1000 broad line AGNs, 80 narrow-line AGNs, and 27,000 “normal” galaxies.