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Cosmological Evolution of Blazars: new findings from the Swift/BAT and Fermi/LAT surveys. M. Ajello [KIPAC/SLAC] L. Costamante, R. Sambruna, N. Gehrels, J. Greiner, J. Tueller, J. Chiang, A. Escala, R. Mushotzky, A. Rau, J. Wall + On behalf of Fermi/LAT collaboration. Instruments. - PowerPoint PPT Presentation
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Cosmological Evolution of Blazars:
new findings from the Swift/BAT and Fermi/LAT surveys
M. Ajello [KIPAC/SLAC]L. Costamante, R. Sambruna, N. Gehrels, J. Greiner, J. Tueller,
J. Chiang, A. Escala, R. Mushotzky, A. Rau, J. Wall+
On behalf of Fermi/LAT collaboration
M. Ajello 2
Instruments
Swift-BATBand: 15-200 keVFoV: 1.4 srMonitor: 70% sky/dayPos. res.: 1’-5’
Fermi-LATBand: 0.1-300 GeVFoV: 2.4 srMonitor: 100%
sky/3hrPos. res.: 3’-21’
M. Ajello 3
Why to study blazars at high-E ?Ajello+, 2008, ApJ, 689, 666
@ hard -rays-Blazars are ~15% of extraG. sources-Evolution of blazars unknown -MeV background unexplained(see Inoue+08 and ref. therein)
@ -rays-Blazars are >85% of extraG. sources-Evolution of blazars studied with EGRET: low numbers-GeV background ?(see Chiang+98,Dermer+05,Narumoto+06)
M. Ajello 4
Ghisellini+99Tagliaferri+00
Pian+98
PKS 0528+134
IBL
HBL
FSRQ
FSRQs and IBL/LBL ‘peak’ in the MeV band
M. Ajello 5
The BAT 3yr Sample
• 38 blazars (26 FSRQs, 12 BL Lacs) detected up to z~4
• 9 FSRQs and 3 BL Lacs in common with EGRET/LAT
• No blazars at low LX and low redshift
Ajello+09,ApJ 699, 603
Seyferts
blazars
M. Ajello 6
Test of Evolution
• Luminosity function needed to assess the contribution of a source class to the diffuse background
Seyferts
Blazars
1. Blazars evolve positively at ~3
2. No significant difference between the 2 sub-classes
3. Seyferts ‘do not’ evolve
M. Ajello 7
Parametric XLF
Luminosity Evolution i.e. objects were more luminous in the past Lx(z)=(1+z)k Lx
Density Evolution i.e. objects were more numerous in the past (L,z)= (L,0) (1+z)k
MethodMaximize Likelihood function based on the product
of Poisson prob. of observing 0 or 1 blazars in a dLxdz element:
(Marshall+83, Borgani+01, Wall+05)
M. Ajello 8
Best-fit XLF for entire population
Best Fit Model:
PLE with a redshift cutoff coupled to a local double power law XLF
Parameters:
1=-0.871.31 <--beaming?2= 2.730.38k= 3.45 0.44=-0.25 0.07 <--3
(Urry&Schafer84)
M. Ajello 9
Separating the populations
FSRQs (26) BL Lacs (12)Best fit model:
PLE: k=3.67, =-0.30Local XLF slope: 2.49 ±0.37
Best fit model:
PLE: k=-0.8±2.4 !!
Local XLF slope: 2.61 ±0.36
Claim of negative (Rector+00, Beckmann+03) or no (Caccianiga+02, Padovani+07) evolution not confirmed/denied
BL Lacs ‘produce’ <1% CXB
M. Ajello 10
The MeV Background
FSRQs
RQ AGN, from Gilli+07
Watanabe+09
•Blazars produce:–10% of CXB @ 2-10 keV–20% of CXB @ 15-55 keV–~100% CXB @ 1 MeV
•FSRQs detected by BAT must peak at ‘MeV’ energy not to violate CXB constraint
•EGRET did not detect high-z BAT blazars. According to Zhang+05, Sambruna+07, Tavecchio+07,
Watanabe+09 they are MeV blazars
FSRQs
RQ AGN, from Gilli+07
M. Ajello 11
The LAT view of blazars
FSRQBL LacRadio GalaxyUncertain
(Abdo et al. 2009, ApJ 700, 597)
• Aug/Sep/Oct high confidence list: 205 sources with >10 detection
• 132 with |b| > 10 (7 pulsars, 14 unid) – 111/125 are bright, flat spectrum radio sources– 98/111 have optical classifications, 89/111 have redshifts
M. Ajello 12
Some Key Properties
F
FSRQs
F
BLLacs
BAT LAT
M. Ajello 13
Blazar Evolution in LAT
FSRQs (59) BL Lacs (29)
Strong Positive EvolutionV/Vm=0.6450.043Power-law slopes: ~2.5
No significant EvolutionV/Vm=0.4220.055
But: 13/42 BL have no z
Power-law slopes: ~2.2
M. Ajello 14
Anti-hierarchical growth
• Larger structures comes first: tracing the merging history of spheroids (eg. Franceschini+99)
• The bulk of super-massive BHs is formed at z~1 : tracing the SFR of galaxies (eg. Madau+99)
• Beaming allows to study AGNs at large z
Hasinger+05
M. Ajello 15
Hasinger+05
Galaxy-AGN co-evolution•SMBHs and galaxies co-evolve through the history of the Universe–MBH-relation (e.g.Merrit&Ferrarese01)
–Co-evolution of SFR and
AGN (e.g. Madau99, Hasinger+05)
M. Ajello 16
AGN-Cluster Interaction
AGNs inflates cavities in the ICM
Total non-thermal pressure in the atmospheres of giant E gal is ~10% (Churazov+09)
Turbulent pressure <5%(Werner+09)
AGN activity
regulate
s the th
ermal s
tate
of the gas b
y injecti
ng energy in
the IC
M Abdo+, ApJ 699, 31
CR pressure <15% (Keith’s talk)
M. Ajello 17
Conclusions
• Blazars in BAT are 15% of total AGN population– Strong evolution (PLE) with evidence for a
redshift peak– They account for ~100% of the MeV background
• Blazars in LAT are the main population:– FSRQs evolve strongly, evolution is complex– BL Lacs seem not to evolve….but wait for a
larger sample
M. Ajello 18
Paucity of blazars at low LX: beaming effect ?
Urry & Shafer+84
Beaming alters the intrinsic luminosity function
->(L)dL = P(L|L) (L)dL
where L=p L
M. Ajello 19
FSRQs
RQ AGN, from Gilli+07
Previous attempts
Comastri+06
Giommi+07
Required to produce ~10% of CXB at 1 keV and not exceed the CXB at ~MeV
Derived from logN-logS of blazar in radio
M. Ajello 20
In deep surveys
• Deep X-ray surveys ‘must’ contain a fraction of blazars
• Selection of C-thick AGN using hardness ratios becomes dangerous
• Unless the evolution of RQ and RL AGN is different…..
logN- logS [0.5-2.4 keV] Courtesy P.
Giommi
blazars
RQ AGN, Hasinger+05
Looking forward to Astro-H/NuSTAR
M. Ajello 21
The BAT survey: Deep, all-sky and Unbiased
• All-sky observed down to ~0.5 mCrab (~6e-12 erg/cm2/s)
• No bias against NH up to Compton-thick regime
2-10 keV @ z=0
2-10 keV @ z=1
15-55 keV @ z=0, z=1
• Chandra/XMM much better sensitivity but smaller FOV and biased
• BAT more sensitive than Suzaku/HXD on long exposures