Chicago Revealing the heavily obscured AGN population with radio selection Wilkes Kuraszkiewicz Atanas Haas Barthel Willner Leipski Worrall Birkinshaw AntonucciOgle ID: 784018
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Slide1
21 Aug 2014
HEAD MeetingChicago
Revealing the heavily obscured AGN population with radio selection
Wilkes, Kuraszkiewicz, Atanas, Haas, Barthel, Willner, Leipski, Worrall Birkinshaw, Antonucci,Ogle, U.T. Cobley & all
Aim: to find ALL the AGN
Slide221 Aug 2014
HEAD MeetingChicago
3CRR: Low-frequency, Radio-selected, Luminous (high L/L
Edd) AGN Selected at 178 MHz: isotropic emission 1<z<2, luminous radio sources (all FRII) Small range in luminosity, redshift (z)→ Orientation effects dominate distribution of properties
Sample:
38 sources: 21 broad line (QSO), 17 narrow-line (NLRG)
Data:
Chandra; Spitzer: IRAC, IRS; Herschel; HST, new optical spectra, wealth of published data
Slide3Powerful, FRII Radio Galaxies21 Aug 2014
HEAD Meeting Chicago
Cygnus A
3CRR, z~1-2,
low-frequency
radio-selected
High L/
L
Edd
, log L~10
45-46
ergs
-1
Orientation
is dominant variable
Slide421 Aug 2014
HEAD MeetingChicago
Chandra X-ray Luminosities for NL+BL AGN
Log Radio Luminosity (5GHz)
Log Hard X-ray Luminosity
Radio (=AGN) Power comparable
X-ray (“observed”)
luminosity of
NL sources 10-1000*
lower
Slide521 Aug 2014
HEAD Meeting Chicago
X-ray Hardness Ratio
Simple Unification: QSO – face-on: bright + soft (Γ~1.9)NLRG – edge-on: faint + hardExceptions:2 QSOs + 1 NLRG: intermediate5 soft NLRG
QSO
NLRG
Soft
X-ray Hardness Ratio
Hard
z~0.5-1, 3CRR
s
Slide6Compton Thick
21 Aug 2014
HEAD Meeting
Chicago
Soft NLRG
QSOs
Intermediate QSOs
X-ray Luminosity is obscured
HR hardens as L
X
decreases
Weakest sources include
2
nd
component: soft excess
Possibilities:
Scattered nuclear light
Extended emission (NLR?)
(Wang et al.)
Jet-related
(
Hardcastle
et al.)
Obscuration
→ decrease
L
x
Hard to
find + measure
obscured sources
HR ≠>
N
H
for low
L
X
Slide721 Aug 2014
HEAD MeetingChicago
Compton Thick? : L
[OIII]/LX4 soft + 5 hard NLRGs:high L([OIII]λ5007)/LX
→
9 Compton Thick (CT)
candidates
X-ray absorption:
HR
→
N
H
~10
20-23
cm
-2
L
[OIII]
/L
X
→
NH
>1024.5cm-2 LX/LR → NH estimate for low S/N sources
Juneau et al. 2011
Edge-on
Radio Core Fraction Face-on
Slide821 Aug 2014
HEAD MeetingChicago
X-ray Absorption vs. Radio Core-Fraction
Strongly correlated→ Observed X-rays are consistent with orientation dependent obscuration of Unified Models
Edge-on
Face-on
Radio Core Fraction
Slide921 Aug 2014
HEAD MeetingChicago
NH Distribution
NLRG NH peaks at high values, >1024cm-2Consistent with z<1 3CRRs (Hardcastle et al 2009)Obscured fraction ~ 0.5 higher than typical 0.1-0.3 for high Luminosity AGNCT fraction ~ 0.2 Consistent with CXRB models (Gilli et al. 2007)
Slide10ConclusionsOrientation alone → range of *1000 in observed LXHigh S/N X-ray spectra required to accurately estimate intrinsic NH and LX → both generally underestimatedUnderestimation of intrinsic LX leads to:High LX AGN: unobscured, #s underestimatedLow LX AGN: obscured,
#s overestimatedThus:Luminosity Functions } increase towards lower LXObscured fractions }
21 Aug 2014
HEAD Meeting
Chicago
Slide11Luminosity Function and obscured fraction21 Aug 2014
HEAD MeetingChicago
Mayo & Lawrence 2013
50% covered
Obscured fraction vs L
X
Change in LF if all are CT
Slide12ConclusionsLuminosity Functions may be flatter, high luminosity active galaxies more numerous than currently deduced A luminosity-dependent obscured fraction may not be required to explain X-ray and optical dataTake care when estimating obscuration for sources in X-ray samples
21 Aug 2014
HEAD MeetingChicago
Slide13Backup Slides
Slide14Unification Scenario
Orientation-dependent obscuration can explain properties of high-L, high-redshift radio sources
Geometry:
19 (50%) QSO
3 (8%) intermediate
8 (21%) NLRGs
8 (21%) CT NLRGs
CT +/-12
o
NL 13
o
Inter. 5
o
QSO +/-60
o
Slide15Summary
Unification model works
Unobscured:CThin:CT= 2.5:1.4:1
Obscured population cannot be identified by X-ray data aloneObscured half of population extends to -2.5 dex in LX
Slide16Low-ionization Emission Line Radio Galaxies (LERGs)
Most FRI + low-power subset of FRII radio sources
(FR: Fanaroff and Riley (1974)
Weak IR (Ogle et al. 2006)Weak, unobscured X-ray emission (Hardcastle et al. 2009)X-ray/IR scale with radio→ Not actively accreting, likely ADAF/ RIAFRemoves change in RG/BL vs L/z in 3CRs No LERGs in z > 1 3CR sample
Slide17Unification vs redshift
Ratio or NL to BL radio sources ~ redshift
1:1 for z
> 1 3:1 for 0.5 < z < 1 4:1 for z < 0.1→ receding torus model, opening angle ↑ with L (Lawrence 1991) OR Unification excluding LERGs
Slide18NERQUAM 23 Haystack Observatory
Why Radio-selection?
Most surveys do not find
all the edge-on AGN Many 3CRR NLRGs fall outside AGN selection regions Low-frequency radio Selects on extended radio structureOrientation measure: core dominanceAge estimate: radio sizeCaveat: only 10% of AGN are radio-loud
Donley et al. (2011) Lacy et al. (2004)
Spitzer IR AGN Selection