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Cosmological Evolution of Blazars: new findings from the Swift/BAT and Fermi/LAT surveys

This paper presents new findings on the cosmological evolution of blazars using data from the Swift/BAT and Fermi/LAT surveys. The evolution of blazars at different energies and the contribution of blazars to the diffuse background are studied. The results show strong evolution of blazars, with evidence for a redshift peak, and suggest that blazars are the main population of AGNs. The implications of these findings for the co-evolution of supermassive black holes and galaxies are also discussed.

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Cosmological Evolution of Blazars: new findings from the Swift/BAT and Fermi/LAT surveys

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  1. 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

  2. Instruments Swift-BAT Band: 15-200 keV FoV: 1.4 sr Monitor: 70% sky/day Pos. res.: 1’-5’ Fermi-LAT Band: 0.1-300 GeV FoV: 2.4 sr Monitor: 100% sky/3hr Pos. res.: 3’-21’ M. Ajello

  3. Ajello+, 2008, ApJ, 689, 666 Why to study blazars at high-E ? @ -rays -Blazars are >85% of extraG. sources -Evolution of blazars studied with EGRET: low numbers -GeV background ? (see Chiang+98,Dermer+05,Narumoto+06) @ hard -rays -Blazars are ~15% of extraG. sources -Evolution of blazars unknown -MeV background unexplained (see Inoue+08 and ref. therein) M. Ajello

  4. Tagliaferri+00 Pian+98 PKS 0528+134 Ghisellini+99 IBL FSRQ FSRQs and IBL/LBL ‘peak’ in the MeV band HBL M. Ajello

  5. Seyferts blazars The BAT 3yr Sample Ajello+09,ApJ 699, 603 • 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 M. Ajello

  6. Seyferts Blazars Test of Evolution • Luminosity function needed to assess the contribution of a source class to the diffuse background Blazars evolve positively at ~3 No significant difference between the 2 sub-classes Seyferts ‘do not’ evolve M. Ajello

  7. Parametric XLF Density Evolution i.e. objects were more numerous in the past (L,z)= (L,0) (1+z)k Luminosity Evolution i.e. objects were more luminous in the past Lx(z)=(1+z)k Lx Method Maximize 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 BestFit Model: PLE with a redshift cutoff coupled to a local double power law XLF Parameters: 1=-0.871.31 <--beaming? 2= 2.730.38 k= 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, =-0.30 Local 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. RQ AGN, from Gilli+07 RQ AGN, from Gilli+07 FSRQs FSRQs • EGRET did not detect high-z BAT blazars. According toZhang+05, Sambruna+07, Tavecchio+07, Watanabe+09they are MeV blazars The MeV Background • 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 Watanabe+09 M. Ajello

  11. The LAT view of blazars (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 FSRQ BL Lac Radio Galaxy Uncertain M. Ajello

  12. LAT BAT BLLacs FSRQs nFn n n Some Key Properties nFn M. Ajello

  13. Blazar Evolution in LAT FSRQs (59) BL Lacs (29) Strong Positive Evolution V/Vm=0.6450.043 Power-law slopes: ~2.5 No significant Evolution V/Vm=0.4220.055 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 AGN activity regulates the thermal state of the gas by injecting energy in the ICM Abdo+, ApJ 699, 31 AGNs inflates cavities in the ICM Turbulent pressure <5%(Werner+09) Total non-thermal pressure in the atmospheres of giant E gal is ~10% (Churazov+09) 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 ? Beaming alters the intrinsic luminosity function ->(L)dL = P(L|L) (L)dL where L=p L Urry & Shafer+84 M. Ajello

  19. RQ AGN, from Gilli+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 FSRQs Giommi+07 Previous attempts Comastri+06 M. Ajello

  20. logN- logS [0.5-2.4 keV] Courtesy P. Giommi blazars RQ AGN, Hasinger+05 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….. Looking forward to Astro-H/NuSTAR M. Ajello

  21. 15-55 keV @ z=0, z=1 2-10 keV @ z=0 2-10 keV @ z=1 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 • Chandra/XMM much better sensitivity but smaller FOV and biased • BAT more sensitive than Suzaku/HXD on long exposures M. Ajello

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