Radio/gamma connection: Study of cm/mm-band radio and gamma-ray - - PowerPoint PPT Presentation

SLIDE 1

Radio/gamma connection: Study of cm/mm-band radio and gamma-ray correlated variability in Fermi bright blazars

Lars Fuhrmann

• S. Larrson, J. Chiang, E. Angelakis, V.

Pavlidou, I. Nestoras, J. A. Zensus et al.

• n behalf of the F-GAMMA & Fermi LAT

collaborations

SLIDE 2

Introduction

do gamma-ray flares usually have radio counterparts? what is the relative timing/delay? where in the jet are the gamma-rays produced (close to BH or pc-scale jet, how far from BH etc.)? several approaches: VLBI studies, fluxr-fluxγ studies, direct light curve analysis… EGRET times - limited studies: ”gamma-ray flares/activities appear to

• ccur during the raising phase (i.e. after the onset) of high frequency

radio flares” i.e. gamma-ray flares happen in the mm-shocks further out! Now we have Fermi/LAT! Many studies emerged Long time baseline needed: now 3 yrs of LAT LCs!

early study:

SLIDE 3

Project overview

The sample and data sets

Aim: a study focusing on the possible connection between

radio and gamma-ray flares/activity periods in the 3 yr long- term light curves of about 60 Fermi-GST detected blazars through a detailed cross-band analysis 1) radio bands: F-GAMMA program since Jan. 2007: 3-4.5 yrs of Effelsberg 100-m/IRAM 30-m monthly monitoring data at 10 different frequencies (110, 60, 36, 28, 20, 13, 9, 7, 3, 2, (1) mm) “the best suitable” 58 1FGL sources (best sampl., frequency & time coverage) sample statistics: cross-band study: selection of 4 frequency bands (3, 9, 20, 60mm)

1 2 3 4 5 6 7 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J0238+1636

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39 5 10 15 20 25 30 35 40 45 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J2253+1608

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39 1 2 3 4 5 6 7 8 9 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J0721+7120

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39

Type # FSRQ 33 BL Lac 17 RG 2 Blazar 5 NLSy1 1

SLIDE 4

Project overview

The sample and data sets 2) Fermi/LAT: 3 yr light curves starting in Aug.

2008

specific time boundaries to best match the radio light curves – start Aug. 15, 2008 RSP pipeline, energy range 0.1 – 300 GeV using power law over that energy range 1FGL sources for ROI, ROI size etc. future: switch to pass 7, 2 FGL sources, more careful spectral model for each source (e.g. broken power law for some etc.), LCs at different energy ranges etc.

1 2 3 4 5 6 7 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J0238+1636

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39 5 10 15 20 25 30 35 40 45 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J2253+1608

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39 1 2 3 4 5 6 7 8 9 54000.0 54500.0 55000.0 55500.0 56000.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

Flux Density (Jy) Time

J0721+7120

2.64 4.85 8.35 10.45 14.60 23.05 32.00 42.00 86.00 142.33 228.39

SLIDE 5

Project overview

The light curves Examples:

5e-08 1e-07 1.5e-07 2e-07 2.5e-07 3e-07 3.5e-07 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J0854+2006

54800 55000 55200 55400 55600 55800 MJD 2 4 6 8 10 12 14 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

5e-06 1e-05 1.5e-05 2e-05 2.5e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J2253+1608

54800 55000 55200 55400 55600 55800 MJD 10 20 30 40 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

SLIDE 6

Project overview

Three different approaches

1) statistical Discrete Cross-Correlation Function (DCCF analysis)

2) fluxr – fluxγ analysis using simultaneous, monthly fluxes 3) direct LC analysis

2e-07 4e-07 6e-07 8e-07 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J1159+2914

54800 55000 55200 55400 55600 55800 MJD 1 2 3 4 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

1e-07 2e-07 3e-07 4e-07 5e-07 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J0721+7120

54800 55000 55200 55400 55600 55800 MJD 2 4 6 8 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

SLIDE 7

1) DCCF analysis

The setup compute DCCFs for each source: for all gamma-ray – radio (ν, ν = 86, 32, 15, 5 GHz) combinations following Edelson & Krolik (1988) caveats: 3yrs – still small number of events, complicated flare structures (multiple sub-flares), “broad DCCFs”, what correlates?, “monthly smoothing” etc. determine significances of correlations: test of chance correlations by mixing source’ gamma-ray LCs: e.g. source 1 (radio) with source 2 to N (gamma-ray), find “upper envelop” confidence levels time lags with uncertainties are estimated by Monte Carlo simulations (Peterson et al.) apply method to the whole sample plus sub-dividing according to FSRQs, BL Lacs, spectral type etc. stacking of DCCFs: increasing the significance, study of averaged behavior of the sample

SLIDE 8

1) DCCF analysis

First results 3mm vs LAT: examples of single source’ DCCFs

• single source cases mostly not significant: ”only” 18 out of 58 sources so far!
• no obvious, simple 1:1 correlation
• not yet long enough data trains
• conservative upper envelops
• 400
• 200

200 400 LAG (Days)

• 0.5

0.0 0.5 1.0 1.5 DCCF

• 400
• 200

200 400 LAG (Days)

• 0.5

0.0 0.5 1.0 1.5 DCCF

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0102 J0050

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0217

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0222

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0237

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0238

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0319

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0336

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0339

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0418

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0423

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0530

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0654

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0721

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

J0730

PRELIMINARY PRELIMINARY PRELIMINARY

• 400
• 200

200 400 LAG (Days)

• 1.0
• 0.5

0.0 0.5 1.0 1.5 2.0 DCCF

SLIDE 9

1) DCCF analysis

First results

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF all sources averaged DCCFs LAT / 3mm radio

PRELIMINARY

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF BL Lacs averaged DCCFs LAT / 3mm radio

PRELIMINARY

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF FSRQs averaged DCCFs LAT / 3mm radio

PRELIMINARY

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF FSRQs BL Lacs averaged DCCFs LAT / 3mm radio

3mm vs. LAT: stacking of DCCFs averaged over whole sample: we start seeing significant correlations ! 99% confidence levels asymmetry All sources: <lag>3mm = 36 days FSRQs: <lag>3mm = -1 days BL Lacs: <lag>3mm = 37 days

PRELIMINARY

SLIDE 10

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF FSRQs BL Lacs averaged DCCFs LAT / 60mm radio

PRELIMINARY

• 400
• 300
• 200
• 100

100 200 300 400 LAG [days]

• 0.2
• 0.1

0.1 0.2 0.3 DCCF all sources averaged DCCFs LAT / 60mm radio

PRELIMINARY

1) DCCF analysis

First results 60mm vs LAT: stacking of DCCFs All sources: <lag>60mm = 197 days FSRQs: <lag>60mm = 197 days BL Lacs: <lag>60mm = 77 / 239 days delay origin: synchrotron self-absorption/opacity

(e.g. Pushkarev et al. 2010)

1) pos. delay: gamma from inside “3mm-core” 2) distance between “gamma-origin” and 86 GHz t=1 surface: Δr ~ 0.8 pc (3mm), ~ 8 pc (60mm) 3) DCCF just sensitive to peaks/mins! which

• riginates first?

SLIDE 11

2) flux-flux analysis

The setup + first results ~ monthly, multi-frequency simultaneous fluxes over 3 years: interpolated LAT fluxes for each radio flux measurement 86 GHz: total number of data points: 1017 (FSRQs: 499, BL Lacs: 359,

• ther: 8)

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

ALL SOURCES

Gamma vs. radio flux

86 GHz / 3mm

PRELIMINARY

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

FSRQs BL Lacs

Gamma vs. radio flux

86 GHz / 3mm

PRELIMINARY

SLIDE 12

2) flux-flux analysis

The setup + first results 32 GHz:

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E > 100 MeV) [ph cm

• 2 s
• 1]

ALL SOURCES

Gamma vs. radio flux

32 GHz / 9mm

PRELIMINARY

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E > 100 MeV) [ph cm

• 2 s
• 1]

FSRQs BL Lacs

Gamma vs. radio flux

32 GHz / 9mm

PRELIMINARY

SLIDE 13

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

ALL SOURCES

Gamma vs. radio flux

14.6 GHz / 20mm

PRELIMINARY

2) flux-flux analysis

The setup + first results

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

FSRQs BL Lacs

Gamma vs. radio flux

14.6 GHz / 20mm

PRELIMINARY

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

ALL SOURCES

Gamma vs. radio flux

4.85 GHz / 60mm

PRELIMINARY

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

FSRQs BL Lacs

Gamma vs. radio flux

4.85 GHz / 60mm

PRELIMINARY

highest frequencies: prominent *apparent* correlation *apparent* correlation vanishes towards lower radio bands

• pacity, core+jet, mm:

more co-spatial! BL Lacs appear mostly uncorrelated ! 15 GHz: 5 GHz:

SLIDE 14

2) flux-flux analysis

The setup + first results BL Lacs different? also at single flux-flux evolutions!

0.1 1 10 100 radio flux density [Jy] 1e-09 1e-08 1e-07 1e-06 1e-05 flux (E>100 MeV) [ph cm

• 2 s
• 1]

HPQs LPQs QSOs BL Lacs

Gamma vs. radio flux

86 GHz / 3mm

PRELIMINARY

• Leon-Tavares et al. (2011): BLLacs

 QSOs  LPQs  HPQs

• sequence in correlation strength

 larger viewing angles? lower D?

• sample: θBLLacs > θFSRQs ?

Dvar (F-GAMMA) and βapp (VLBI kinematics)  θv

4 8 12 16 20 24 28 32 36 40 44 Viewing angle [deg] 2 4 6 8 10 12 14 Number all sources FSRQs BL Lacs RG Viewing angles @ 15 GHz

PRELIMINARY

mean: 6.1o (FSRQs), 14.5o (BL Lacs) median: 5.1o (FSRQs), 10.7o (BL Lacs)

SLIDE 15

2) flux-flux analysis

The setup + first results BUT: common distance bias! simultaneous LC fluxes: increasing (flux) statistics without extending the luminosity dynamical range ! statistical analysis (Pavlidou et al. 2011, Ackermann et al. 2011) 3mm: BL Lacs: r-value (Pearson product-moment): 0.377, significance: <10-5 FSRQs: r-value: 0.474, significance: 0.047 60mm, BL Lacs: r-value: 0.2, significance: 0.006 FSRQs: r-value: 0.32, significance: 0.99 no significant *intrinsic* correlation sequence ! but frequency dependence significant!

SLIDE 16

3) Direct LC analysis

The setup + first results DCCF analysis: timing of radio/γ-ray peaks/minima,

• pacity in the core etc.

additional LC information: relative timing/occurrence/onset of radio/ γ-ray events to constrain location (e.g. Leon-Tavares et al. 2011) “time delays”: distance of max. γ –ray production region from radio/ mm shock onset downstream of radio core

gamma radio t S

activity period

SLIDE 17

3) Direct LC analysis

The setup + first results mm-flux often already raising during γ-ray flares machinery to obtain LC parameters difficult task!

t

2e-07 4e-07 6e-07 8e-07 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J1159+2914

54800 55000 55200 55400 55600 55800 MJD 1 2 3 4 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

1e-07 2e-07 3e-07 4e-07 5e-07 flux (E>100 MeV) [ph cm

• 2 s
• 1]

Fermi LAT

J0721+7120

54800 55000 55200 55400 55600 55800 MJD 2 4 6 8 flux density [Jy] 3mm PV 9mm EFF 20mm EFF 60mm EFF

PRELIMINARY

SLIDE 18

3) Direct LC analysis

The setup + first results # of prominent γ-flares: 44 S3mm[γ-peak] / <S3mm>

t

0.5 1 1.5 2 2.5 3 S_flare / <S> 5 10 15 20 Number all sources/flares 86 GHz / 3mm

86.4%

SLIDE 19

Conclusion

1) statistical Discrete Cross-Correlation Function (DCCF analysis) single sources: often DCCFs still not significant! 18 cases so far! but stacking: significant correlations, radio lagging (3mm: 36 days, 60mm: 197 days), opacity: Δr ~ 0.8 pc (3mm), ~ 8 pc (60mm) 2) fluxr – fluxγ analysis using simultaneous, monthly fluxes possible flux-flux correlations mostly apparent due to distance bias! but frequency dependence robust! 3) direct LC analysis difficult task to obtain proper LC parameters/values mm-flux high during γ-ray flares for ~ 90 % of the cases!