X-ray%20Bright,%20Optically%20Normal%20Galaxies%20-%20XBONGS%20Forman,%20Anderson,%20Hickox,%20Jones,%20Murray,%20Vikhlinin,%20Kenter%20and%20the%20Bootes%20Team

1
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)
2
The XBootes Survey

• 126 ACIS 5 ksec pointings
• Joint GTO (Murray) and GO (Jones) program
• 14h 32m 34? 06
• 4642 sources detected (gt2 cts)
• 625 spurious
• 3293 sources detected (gt4 cts)
• 22 spurious
• 42 extended sources (gt10 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
3
Spectroscopy in Bootes

• MMT/Hectospec fiber spectrograph
• 300 fibers
• 6 A resolution, 4000-8000A
• Spectroscopy
• Complete X-ray gt4 cts and Ilt21.5 and galaxies
  Ilt19.5
• 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 lt z lt 1

4
Heterogeneous Class of Objects

• From optical SEDs and morphology
• Red Ellipticals 60
• Blue Ellipticals 84
• Interacting 21
• Spirals 9
• AGN 12
• (Fioc Rocca-Volmerange 1997 Francis et al. 1991)

5
Redshift Distribution
XBONGS Broad line AGN Narrow line AGN
XBONGS and NL AGN same distribution
6
XBONG Magnitude Distribution
XBONG BL (zlt1) 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
7
Luminosity Distributions

• 200 XBONGs with Lxgt1042 erg/s
• 50 with Lxgt1043 erg/s
• XBONGs and NL AGN
• Similar Lx
• Similar Fx/FR
• Argues against dilution for all of
• sample

XBONG BL (zlt1) NL
8
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

9
IRAC Color-Color Diagrams (following Stern et al.)
BL AGN
XBONGS BL AGN NL AGN
0.45ltZlt0.60
Zlt0.15
0.60ltZlt0.75
0.15ltZlt0.30
Red Blue
0.75ltZlt1.00
0.30ltZlt0.45
zlt0.3 Dilution - about 30 consistent with
Georgantopoulos et al.
dilution criterion zgt0.3 XBONGS
concentrated under AGN wedge
10
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 lt 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 lt 0.01
• VIABLE MODEL - needs detailed SEDs

11
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
  nH1022 cm-2
• Many sources show little (lt1022 cm-2) absorption
• RIAF (radiatively inefficient accretion flow)
• Spheroidal sample has low Eddington ratio
  (Lbol/Leddlt0.01)
• Probably some BL Lacs
• XBONGs are a heterogeneous class

12
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 SEDs 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

13
(No Transcript)
14
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.