X-ray Bright, Optically Normal Galaxies - XBONGS Forman, Anderson, Hickox,

Jones, Murray, Vikhlinin, Kenterand the Bootes Team

Bootes Survey9.3 sq. degrees with Chandra

4632 X-ray sources1600 optical spectra

NOAO Deep Wide Field SurveyAGES Optical Spectroscopic Survey

20,000 galaxy spectraKey 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 (>=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 (R26)

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 >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

4

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)

5

Redshift Distribution

XBONGS Broad line AGNNarrow line AGN

XBONGS and NL AGN same distribution

6

XBONG Magnitude Distribution

XBONGBL (z<1) NL

XBONG counterparts similar to NL/BL AGNpossibly somewhat fainter than NL AGN

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

7

Luminosity Distributions

XBONGBL (z<1)NL

•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

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.)

Z<0.15

0.15<Z<0.30

0.30<Z<0.45

0.45<Z<0.60

0.60<Z<0.75

0.75<Z<1.00

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

z>0.3 XBONGS concentrated under AGN wedge

XBONGS BL AGNNL AGN

Red Blue

BL AGN

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 < 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

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 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

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 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

13

14

MMT Bootes surveyOptical spectroscopy: AGES survey w/ MMT/Hectospec

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