Gamma-Rays from Radio Galaxies: Fermi-LAT PAOLA GRANDI INAF/IASF - PowerPoint PPT Presentation

Gamma-Rays from Radio Galaxies: Fermi-LAT PAOLA GRANDI INAF/IASF BOLOGNA, ITALY on behalf of the FERMI LAT Collaboration Many thanks to : C. Dermer. G. Ghisellini, L. Maraschi, G. Migliori, E. Torresi, R. Aversa, V. Bianchin HEPRO III High Energy Phenomena in Relativistic Outflows III Barcelona, June 27 - July 1, 2011 Monday, July 11, 2011

Fermi (GLAST) Gamma-ray Space Telescope Launched on 11 June 2008 Fermi consists of two instruments: the Large Area Telescope : LAT (20 Mev -300 GeV) the Gamma-ray Burst Monitor : GBM (8 keV -40 MeV). Monday, July 11, 2011

The LAT is an imaging high-energy gamma-ray telescope ! ! "#$!%&"!'(!)!*)'+,-./0$+('./!1$2$(-.*$!3'1#!)! *+$-'('./!1+)-4$+!)/5!-)2.+'6$1$+! FOV =2.3 sr ~ 1/5 of the full sky It scans the entire sky in about 3 hr • On-axis effective area � 1500 cm 2 100 MeV to � 8000 cm 2 at E � 1 GeV • Energy resolution better than 10% between � 50 MeV and � 50 GeV. • Spatial resolution depends on the photon energy R 68 � 0.6 � at E � 1 GeV Monday, July 11, 2011

BL LACs The Fermi sky 1 year FSRQs Other Extragalactic Sources 90 60 The clean sample of the First Catalog 30 of AGN (1LAC) contains 599 sources 180 150 120 90 60 30 0 -30 -60 -90 -120 -150 -180 Abdo, A. A., et al. 2010a, ApJ, 715, 429 (1LAC); Abdo, A. A., et al. 2010b, ApJS, 188, 405 (1FGL) -30 -60 -90 2 years In the Second Catalog of AGN (2LAC, in preparation) , the number of detected AGNs is increased by more than 40% (877 sources). preliminary Monday, July 11, 2011

A small angle of view implies a strong amplification of the jet emission. δ =1/ Γ (1- β cos θ ) The Doppler factor relates intrinsic and observed flux for a moving source at relativistic speed v =  c . For an intrinsic power law spectrum: Blazar F’(  ’) = K (v’) -a the observed flux density is Γ F  (  )=  p F’  ’ (  ) p=f(  ) Monday, July 11, 2011

The majority of Extragalactic Sources are BL LAC and FSRQs However ~3% of the  -sources are not Blazars The “other” Extragalactic Sources belongs to two broad classes of objects reflecting two different particles acceleration processes: 1.
 SNR as particle accelerator -- SNR expanding shocks -> CR acceleration ->  - rays Starburst Galaxies h9p://wwwmagic.mppmu.mpg.de/magic/index.html 2.
AGN
as
par0cle
accelerator

‐>
Jets Narrow Line Seyfert 1 Sources (Foschini’s Talk) Misaligned AGNs 


























































 Monday, July 11, 2011

After 24 months of sky survey Non-Blazars BLAZARs preliminary Monday, July 11, 2011

2.
AGN
as
par0cle
accelerator:
Misaligned
AGN
(MAGN) With MAGNs we intend Radio Sources (Radio Galaxies and SSRQs) with the jet not directly pointed towards the observer. MAGNs Γ NLRG MAGNs BLRG


 SSRQs BL
LACs Blazars FSRQS 8 Monday, July 11, 2011

MAGNs show: Resolved
and
possibly
symmetrical
 Steep
radio
spectra
 and/or structure
in
radio
map
  r >0.5 FRI are considered the PARENT POPULATION of BL LACs FRII are considered the PARENT POPULATION of FSRQs (SSRQs are in between) Monday, July 11, 2011

FIRST SAMPLE of MAGNS (15 MONTH-DATA) Abdo, A. A., et al. 2010, ApJ, 720, 912 (MAGN) MAGNs are generally faint and soft sources F(>0.1 GeV)~10 -8 Phot cm -1 s -2   2.4 FRII SSRQ FR I Radio Galaxy Monday, July 11, 2011

LAT COUNTER-PARTS OF 4 COMPLETE RADIO SAMPLES 3CRR sample  =178 MHz Molonglo Southern 4Jy sample MS4  =408 MHz F> 10.9 Jy F> 4 Jy 173 sources 228 sources 2Jy sample declination+10° and redshift z<0.7. 3CR sample  =178 MHz  =2.7 GHz F> 9 Jy F> 2 Jy 113 sources 88 sources 3CR+3CRR+MS4+2JY= North-south-RADIO SAMPLE 0<z<2.5 29<Log (L 178 MHz) <37 erg s -1 Monday, July 11, 2011

Rate of Detections (%) Source with TS >25 15 and 24 months of sky survey preliminary 1 � 0.9 � 0.8 � 32 Sources with TS>25 0.7 � (TS) 1/2 ~  0.6 � 0.5 � 0.4 � 0.3 � 0.2 � 0.1 � 0 � FRI � FRII � FSRQ � BL LAC � SB � AGU � FRII are the less detected objects The  -ray elusiveness of FRIIs has been also confirmed by a dedicated study of Broad Line Radio Galaxies (Kataoka et al. 2011, ApJ submitted) Monday, July 11, 2011

Are FRIIs elusive GeV sources because too far? Maybe not! preliminary Log (f  ) 1 GeV = a + b x Log(f  ) 5 GHz a b r P_r TOT 6.2 0.6 0.65 99.9% (1.6) (0.2) TS>25 MAGN 7.9 0.4 0.66 97.4% (1.2) (0.1) TS>25 Ghirlanda et al. 2011 The Radio  ray fluxes are correlated see also, Ackermann et al. 2011 ApJ in press CA: Giroletti et al. Monday, July 11, 2011

Predicted fluxes @ 1 GeV of the 3CR+3CRR+MS4+2Jy sources: a first “qualitative” approach Observed Predicted Log (f  ) 1 GeV = a + b x Log(f  ) 5 GHz correlation based only on FRI+FRII objects correlation based on the total sample A large number of FRIIs should cross over the LAT sensitivity threshold. In spite of this, only an handful of FRIIs is seen at GeV energies Monday, July 11, 2011

Radio Flux indicates that the core of FRIIs is bright enough to be visible at very high energies Why does Fermi-LAT preferentially catch FRIs and lose FRIIs ? We do not have a firm answer to that. We are trying to understand looking at the SED of single Radio Galaxies Monday, July 11, 2011

FRI jets are complex strucures: a single SSC zone model does not work M87 SSC one zone model Emission from sub-parsec scale jet (core) as suggested by One simple zone SSC model 2008 VHE Chandra VLBA monitoring  � = 1.8 � = 2.3 � = 25° B=0.05 G R=2x10 18 cm � =10°, � =2.3 , � =3.9  n= � -p p=2.1 800 � � � 960 p=3.1 960< � � 4x10 5 n = k � -p p=1.6 [1, 4x10 3 ] p=3.6 [4x10 3 , 10 7 ] R=1.4x10 16 cm P jet ~ 10 44 erg sec -1 B=55mG Abdo et al. 2009, ApJ ,707, 55 Abdo et al. 2009, ApJ , 699, 31 CA:Chung & McConville (CA:Kataoka) Monday, July 11, 2011

Nuclear SED Modeling NGC6251 Model Parameters: Egret =25 o = 2.4 R~10 17 cm B~0.04 G Fermi- 
 N=K  -p p 1 =2.76 p 2 =4.04 LAT 
 K~2 × 10 6 cm -3 break =2 × 10 4 







 min =250 max =2 × 10 5 The SSC jet is slow compared to typical BL Lac jets (as for other FRIs in LAT MAGN sample) see talk of Giulia Migliori Monday, July 11, 2011

Possible solutions to the problems (not the only ones)  Decelerating jet (Georganopoulos & Kazanas 2003)  Structured (spine +slower layers) jet (Ghisellini, Tavecchio & Chiaberge 2005) The jet is structured The jet is decelerated Γ 2 Γ 1 In these models, there is an efficient (radiative) feedback between different regions in the jet that increases the IC emission Monday, July 11, 2011

In these models, there is an efficient (radiative) feedback between different regions in the jet that increases the IC emission 19 Monday, July 11, 2011

The case of 3C120: radio classified as FRI but hosting a very efficient accretion flow β sin θ β sin θ β a = β a = 1 − β cos θ 1 − β cos θ 3C120 β sin θ β a = 1 − β cos θ Monday, July 11, 2011

The inner spine could be the dominant source of  -ray photons (3C120 could be an example of Radio Galaxy with an efficient accretion disk: FRII type?). • Stratified/decelerating jet not required •  v =10-15° and  =7 can fit the data, the jet is not too slow Grandi, Ghisellini, Maraschi et al. in prep 15month-LAT data Monday, July 11, 2011

Conclusions Gamma-rays in extragalactic sources are signatures of two different engines responsible of particle accelerations: SNR -> CR + dust +field of radiation working in Starburst galaxies Black Hole -> jet + external photons working in AGNs 97% of the Fermi sources are BL LACs and FSRQs. 3% are other kind of objects: NLSy1, SB and MAGNs. The MAGN class is mainly populated by FRI radio galaxies. The presence of a stratified jet in these sources seems to favor their detection. On the contrary, FRIIs are difficult to detect in gamma. The study of all the gamma-counterparts of 4 complete radio catalogs indicates a correlation between the radio core (5 GHz) and gamma (1 GeV) fluxes (essentially driven by Blazars and FRIs). On the basis of this correlation a quite large amount of FRIIs is expected to be observed at GeV energies, BUT only 3-4 FRIIs ARE actually observed above 100 MeV. The radio-gamma flux correlation weakens the hypothesis that the FRIIs are missed because too far (and thus too weak) . Are FRII jets spine dominated? Monday, July 11, 2011