Parsec-Scale Jet Properties of Fermi-detected AGN

Transcription

1 Parsec-Scale Jet Properties of Fermi-detected AGN Matthew Lister (Purdue) for the MOJAVE Team Montage by M. Kadler et al.

2 MOJAVE Collaboration M. Lister (P.I.), N. Cooper, B. Hogan, T. Hovatta S. Kuchibhotla (Purdue) T. Arshakian, C.S. Chang, L. Fuhrmann, A. Lobanov, A. Pushkarev, T. Savolainen, J. A. Zensus (Max Planck Inst. for Radioastronomy) FmJ 2010 M. and H. Aller (Michigan) M. Cohen (Caltech) D. Homan (Denison) M. Kadler (U. Erlangen-Bamberg) K. Kellermann (NRAO) Y. Kovalev (ASC Lebedev) E. Ros (U. Valencia) N. Gehrels, J. McEnery, R. Sambruna, J. Tueller (GSFC) We thank the LAT team and Moritz Böck for providing us with LAT data/analysis. The MOJAVE Program is supported under NASA Fermi Grant NNX08AV67G and NSF grant AST. Fermi Monitoring Of Jets in Active Galaxies with VLBA Experiments Very Long Baseline Array

3 Fermi-Jansky Connection Remarkable synergy in extragalactic sky between Ɣ- ray and high freq. radio regimes Three-month (LBAS) Fermi catalog: 54% identified with VLBI radio sources (Kovalev 2009, ApJL 707) 1FGL (11-month) Fermi catalog majority of sources outside galactic plane have flat-spectrum blazar associations (Abdo et al ApJS 188) 43% of southern 1FGL are associated with AT20 GHz catalog. Fermi detection rate is ~100% for brightest AT20 GHz sources (Mahony et al. 2010, Ghirlanda et al. 2010) AGN gamma-ray emission is directly connected with beamed relativistic jets

4 Ɣ-ray vs. VLBA radio core flux VLBA measurement 2.5 ± 0.2 months after 1FGL meas. MOJAVE sample: Pushkarev et al. arxiv

5 Ɣ-ray vs. high frequency radio flux AT 20 GHz sample: Mahony et al. arxiv

6 What makes an AGN γ ray bright? High current activity state Kovalev et al. ApJ 696, L17 High-peaked spectral energy distribution Abdo et al. 2010, ApJ 716,30 Preferred jet viewing angle Pushkarev et al., 2010 A&A 507, L33; Savolainen et al A&A 512, A24; Ojha et al. arxiv High jet Lorentz factor Lister et al. ApJ 696, L22; Savolainen et al A&A 512, A24

7 MOJAVE-1 Sample Selected on 15 GHz VLBA radio flux density multi-year ( ) flux threshold criterion frequent VLBA epochs back to 1994 for most sources Complete in sky region above dec -20 obscuration not an issue at high radio frequency 135 sources, redshifts are 95% complete sample dominated by flat-spectrum blazars 61% have a LAT 1FGL association Radio-selected Lister et al., 2009, AJ, 137, 3718 Lister & Homan 2004, AJ 130, 1389

8 1FM Sample FmJ 2010 Brightest 124 AGN in 1FGL (median energy flux): sky region: b > 10, dec > -30 brightest 1FGL sources not as affected by source confusion, background subtraction, LAT PSF and energy response Rejected 25 radio weak AGN: less than 0.2 Jy compact radio flux density at 15 GHz (from Fermi launch through ) Final 1FM sample has 99 AGN 43 of these are in MOJAVE-1 (i.e., radio-bright---ɣ-bright) Ɣ-ray-selected (Lister et al., in prep.)

9 What makes an AGN γ ray bright? Complex combination of: High current activity state Kovalev et al. ApJ 696, L17 High-peaked spectral energy distribution Abdo et al. 2010, ApJ 716,30 Preferred jet viewing angle Pushkarev et al., 2010 A&A 507, L33; Savolainen et al A&A 512, A24; Ojha et al. arxiv High jet Lorentz factor Lister et al. ApJ 696, L22; Savolainen et al A&A 512, A24

10 Blue = Radio-selected blazars (MOJAVE-1) Red = Gamma-ray selected blazars (1FM) Decl. > - 30 b > 10 A B ( 25 1FGLs in this region ) 1FM Ɣ-ray limit (Incomplete in this region) D MOJAVE-1 completeness limit ( ) C

11 Outer = 1FM + MOJAVE-1 (all sources) Low radio activity state High radio activity state FmJ 2010 Comparison of 15 GHz VLBA median flux densities in pre- and post LAT era: brightest 1FGL sources are in high radio activity states similar result found for 3-month list by Kovalev et al. 2009, ApJL

12 Jet Activity States At any given time, only the energized portion of a broader jet is visible Stacked image: FmJ 2010 Activity states of AGN jets evolve over time long quiescent periods with no blob ejections new blobs ejected at new position angles only 30% of the 3 month LAT AGN were detected by EGRET Image 13yrs later: from June March Lister et al., 2009, AJ, 137, 3718

13 Jet Activity States Are changes in pc-radio jet emission and morphology reflected in the gamma-ray YES results of activity? Boston U. group on 3C454.3 (Jorstad et al. 2010), (Marscher et al. 2010), & this meeting. Jorstad et al., these proceedings Does the jet beaming factor change with activity state? SED modeling of Abdo et al. ApJ 716, 835 suggests higher Doppler factors in high states

14 What makes an AGN γ ray bright? Complex combination of: High current activity state Kovalev et al. ApJ 696, L17 High-peaked spectral energy distribution Abdo et al. 2010, ApJ 716,30 Preferred jet viewing angle Pushkarev et al., 2010 A&A 507, L33; Savolainen et al A&A 512, A24; Ojha et al. arxiv High jet Lorentz factor Lister et al. ApJ 696, L22; Savolainen et al A&A 512, A24

15 Spectral Energy Distributions (SEDs) High fraction (42%) of 1FGL catalog are BL Lacs 86% of MOJAVE-1 BL Lacs are LAT-associated but only 57% of MOJAVE-1 quasars Sensitivity of LAT favors high-peaked SED objects (Abdo et al. 2010, ApJS 188, 405) Moving SED peak to higher energy means lower un-beamed radio-to-ɣ-ray flux ratio

16 Mrk 421 FmJ 2010

17 Blue = Radio-selected blazars (MOJAVE-1) Red = Gamma-ray selected blazars (1FM) No HBL in MOJAVE-1 A B (25 AGN in this region) 1FM Ɣ-ray limit (Incomplete in this region) D MOJAVE-1 completeness limit ( ) C

18 Soft Hard High-SED peaked Blue: 1FM-in-MOJAVE-1 (radio selected) Red: 1FM-non-MOJAVE-1 (Ɣ-ray selected) Harder energy index means IC peak lies at higher energy (Abdo et al. 2010, ApJ 716,30)

19 Why are these bright lowspectral-peaked LAT AGN radio weak? Blue: 1FM-in-MOJAVE-1 (radio selected) Red: 1FM-non-MOJAVE-1 (Ɣ-ray selected)

20 What makes an AGN γ ray bright? Complex combination of: High current activity state Kovalev et al. ApJ 696, L17 High-peaked spectral energy distribution Abdo et al. 2010, ApJ 716,30 Preferred jet viewing angle Pushkarev et al., 2010 A&A 507, L33; Savolainen et al A&A 512, A24; Ojha et al. arxiv High jet Lorentz factor Lister et al. ApJ 696, L22; Savolainen et al A&A 512, A24

21 Blue = Radio-selected blazars (MOJAVE-1) Red = Gamma-ray selected blazars (1FM) max viewing angle = δ -1 A B (25 AGN in this region) 1FM Ɣ-ray limit (Incomplete in this region) D C

22 Apparent Jet Opening Angles 3month MOJAVE-1-LAT generally have broader apparent opening angles than non-lat similar result found for TANAMI (Ojha et al. 2010, arxiv ) MOJAVE/LAT/TeV HBL Overall intrinsic opening angle distributions are similar The bright LAT blazar jets are typically viewed closer to the line of sight Pushkarev et al., 2009 A&A, 507, L33

23 MOJAVE-1: AGN in 3 month LBAS list oriented closer to line of sight than non-lbas FmJ 2010 In moving jet frame, a deficit of LBAS jets viewed end-on possible anisotropy in restframe gamma-ray emission pattern off-axis mini-jet emission model of Giannios et al. 2010, MNRAS 402, 1649 selection effects currently being studied for 1FM sample Savolainen et al., 2010 A&A, 512, A24

24 Doppler boosting Unbeamed Ɣ-ray flux Unbeamed radio flux

25 Doppler boosting Beamed Ɣ-ray flux Equal boosting in both regimes preserves fluxflux correlation Beamed radio flux

26 Doppler boosting Beamed Ɣ-ray flux Unequal boosting destroys linear correlation: produces an upper envelope Beamed radio flux

27 Many emission models (nonsteady jet: Lyutikov & Lister 2010; ECS: Dermer 1995; ) predict higher boosting in Ɣ-rays than radio Highest-boosted AGNs should lie on the top edge of the flux-flux envelopenon-lat Lister 2007, 1 st GLAST Symposium - Monte Carlo radio flux-limited AGN sample - low intrinsic gamma-ray radio lum. scatter - Ɣ-rays boosted more than radio

28 QSOs in region A should have higher Doppler factors and lower un-beamed radio powers than region C. A B (25 AGN in this region) 1FM Ɣ-ray limit (Incomplete in this region) D C

29 Apparent Jet Speeds LAT has detected all of the fastest known jets Г = 40 Г = 20

30 Shaded: QSO Unshaded = BL Lacs Savolainen et al., A&A 512, A24 Doppler Factors MOJAVE-1 LBAS jets have significantly higher Doppler factors than MOJAVE-1 non-lbas. Variability Doppler factor Hovatta, this meeting Doppler factor increases with Ɣ-ray flux in radioselected MOJAVE-1 sample Variability Doppler Factor LBAS = LAT 3 month AGN list

31 Summary 1. Several factors determine whether an AGN is γ-ray loud: more likely to see Ɣ-rays while pc-scale jet is in active radio state high-energy peaked-bl Lacs are more prevalent at fainter Ɣ-ray levels the primary factor is Doppler boosting of pc-scale jet emission FmJ Doppler boosting model predicts an envelope (not a linear correlation) in radio- γ-ray flux-flux plot time lags and variability pose strong challenges for analysis 3. The radio-weak/ɣ-ray bright LSP quasars should have large Doppler factors according to beaming statistics should have much lower intrinsic radio powers than radio-bright/ɣ-weak essential to obtain information via VLBA proper motion and EVLA studies

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33 What radio-ɣ-ray ray time delay gives the best flux-flux correlation? VLBA measurement 2.5 ± 0.2 months after 1FGL meas. Radio emission lags Ɣ-rays by 1-8 months in our frame (~1 month in host galaxy frame) Pushkarev et al. 2010, arxiv

34 Blue = Radio-selected blazars (MOJAVE-1) Red = Gamma-ray selected blazars (1FM) Decl. > - 30 b > 10 A B (25 AGN in this region) 1FM Ɣ-ray limit (Incomplete in this region) D MOJAVE-1 completeness limit ( ) C