multiwavelength observations of the gamma-ray blazars detected by agile filippo d’ammando inaf -...

Multiwavelength observations of the gamma-ray blazars detected by AGILE

Filippo D’Ammando

INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica RomaINAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma

Università degli Studi di Roma “Tor Vergata”Università degli Studi di Roma “Tor Vergata”

Ph.D in Astronomy - Cycle XXII Ph.D in Astronomy - Cycle XXII

Roman Young Researchers Meeting 2009

Active Galactic Nuclei - Unification ModelActive Galactic Nuclei - Unification Model

• central Black Hole (106 -109 Mʘ)

• accretion disk rotating around the SMBH

• clouds of gas gravitational attracted by the black hole and illuminated by the disk radiation

• optically thick torus of molecular gas and dust

• two collimated relativistic jets

Urry and Padovani 1995

RYRM 2009 Filippo D’Ammando 21 July 2009

Almost all galaxies contains a massive black hole but 99% of them are silent and 1% is active (mostly radio-quiet AGNs)... and only 0.1% is radio-loud AGNs

Blazar characteristics:

- compact radio core, flat or inverted spectrum

- apparent superluminal motion

- irregular, rapid and often very large variability at all frequencies

- high and variable polarization at optical and radio frequencies


Emission mechanisms in blazars

Leptonic processes:

- synchrotron emission

- inverse Compton where seed photons came from the internal synchrotron radiation

- inverse Compton where seed photons came from external radiation (accretion disk, BLR and/or torus)

Hadronic processes:

- synchrotron emission

- proton-initiated cascades

- proton-synchrotron emission


Synchrotron SSC

Synchrotron Self-Compton (SSC)Synchrotron Self-Compton (SSC)Electrons in a magnetic field can work twice: first producing

synchrotron radiation, and then Comptonizing it (SSC)


Sikora, BegelmanSikora, Begelman and Rees 1994 and Rees 1994

In External Compton model the seed photons come from outside to the jet


The blazar (spectral) sequenceThe blazar (spectral) sequence

Fossati et al. 1998 Donato et al. 2001

FSRQ

BL Lac

Epk of synchrotron and Compton components inversely correlated with L

L

peakRYRM 2009 Filippo D’Ammando 21 July 2009

Low power slow cooling large ɣpeak

Big power fast cooling small cooling small ɣpeakpeak

Ghisellini et al. 1998, 2002


Giuliani, D’Ammando, Vercellone, et al. 2009, A&A, 494, 509

First extragalactic source detected in gamma-ray by AGILE-GRID, monitored simultaneously in optical band by REM telescope and in X-rays by Swift

<Fɣ> = (210 38) 10-8 ph cm-2 s-1 E > 100 MeV

Gamma-ray flux similar to the EGRET high state but soft spectrum

The soft spectrum during a flaring episode could be an indication of a dominant contribution of EDC emission compared to ECC emission model

9 - 13 July 2007

First AGILE multi-λ campaign: 3C 279

ECDECD

ECCECC


R-band light curve between December 2006 and December 2007: a strong minimum occurred about 2 months before the AGILE observation

This optical minimum might be correlated with a low accretion state of the disk and then with a ECC component deficit, delayed of about two months

Hartman et al. 2001


Pucella, Vittorini, D’Ammando, et al. 2008, A&A, 491, L21

<Fɣ> = (195 30) 10-8 ph cm-2 s-1 E >100 MeV

Possible correlation between optical and gamma-ray bands: contemporaneous decrease in fluxes

The IC contribution from the BLR can explain the observed hard gamma-ray spectrum

23 August - 1 September 2007

PKS 1510-089


D’Ammando, Pucella, Raiteri, et al., submitted to A&A

Serendipitous detection during an AGILE pointing towards the Galactic Center

3 ToO by Swift/XRT: the spectrum becomes harder when the source is brighter

GASP-WEBT observed intense optical activity between January and April 2008

17 - 21 March 2008

PKS 1510-089: a rapid gamma-ray flare in March 2008


Between January and April 2008, the blazar PKS 1510-089 showed intense optical activity with several episodes of fast variability detected by GASP - WEBT

Peaks was detected in the optical band on 15 February, 29 March and 11 April 2008

After two episodes of medium intensity the

source was not detected for some days in

gamma-ray band and suddenly a rapid flare

was observed by AGILE on 18-19 March 2008


Radio-to-optical behaviour

The light curve at 230-345 GHz suggests that the mechanism producing the flaring event observed in optical in the second half of February and in late March-April 2008 also interested the millimetric emitting zone, with some delay

At 22-43 GHz a hint of flux increase is visible in the second part of the light curve, while the radio flux at 5-15 GHz shows no trend


Spectral Energy Distribution - March 2008

Likely signatures of the little and big blue bumps

hard X-ray spectrum: soft X-ray excess?


PKS 1510-089 showed an extraordinary gamma-ray activity

during March 2009, with several flaring episodes

D’Ammando et al., in preparation

PKS 1510-089 March 2009


GASP observations of PKS 1510-089

During March 2009 the optical activity of PKS 1510-089 is greatly increased with a peak on 26 March 2009

D’Ammando et al., in preparation


Chen, D’Ammando, Villata, et al. 2008, A&A, 489, L37

<Fɣ> = (97 15) 10-8 ph cm-2 s-1 E >100 MeV

with a peak level of (193 42) 10-8 ph cm-2 s-1

z = 0.31 0.08 (Nilsson et al., 2008)

Total power transported in the jet is extremely

high ( Ltot > 3 x 1045 erg s-1) , at the limit of the

maximum power generated by a spinning black

hole of 109 Mʘ

4 - 23 September 2007

S5 0716+714 in September - October 2007


The Discrete Correlation Function (DCF) displays a significant peak for a time-lag of -1 day

Possible delay in the gamma-ray flux variations with respect to optical variations of the order of 1 day

To fit the SED we use 2 different SSC components:

- the first component reproduces the ground state

- the second components dominates the optical and gamma-ray bands


Giommi, Colafrancesco, Cutini, et al., 2008, A&A, 487, L49

<Fɣ> = (47 ± 11) 10-8 ph cm-2 s-1 E >100 MeV

The gamma-ray flux is about a factor of 2 lower than in September

Strong variability in soft X-ray, moderate variability at optical/UV and approximately constant behavior in hard X-rays

The SED is consistent with a two-components SSC model

23 October - 13 November 2007

Swift and AGILE simultaneous obs. in October - November 2007


Pacciani, Donnarumma, Vittorini, et al. 2009, A&A, 494, 49

<Fɣ> = (22 6) 10-8 ph cm-2 s-1 E >100 MeV

Fɣ [peak] = (33 11) 10-8 ph cm-2s-1 E >100 MeV

Multi-wavelength campaign: REM, Swift, RXTE, INTEGRAL and AGILE

No optical variability during the entire campaign. Hint of a possible anti-correlated variability

between X-rays and gamma-rays

SSC + EC: spectral variability consistent with an acceleration episode of the electron population

16 December 2007 – 8 January 2008

3C 273: simultaneous detection by GRID & SA


Vercellone, Chen, Giuliani, et al. 2008, ApJL, 676, 13

AGILE repointing the source during a period of strongly enhanced optical emission

<Fɣ> = (280 ± 40) 10-8 ph cm-2 s-1 E >100 MeV

Highest gamma-ray flux from this source in the last 15 years but see Fermi obs.

3C 454.3: July 2007

24 - 30 July 2007


MW Observations of 3C 454.3 in November 2007

10 November - 1 December 2007

Vercellone, Chen, Vittorini, Giuliani, D’Ammando et al. 2009, ApJ, 690, 1018

<Fɣ> = (170 13) 10-8 ph cm-2 s-1, with a peak of ~400 x 10-8 ph cm-2 s-1 E >100 MeV

Rapid variability in the optical band

Emission in the optical range appears to be correlated with that at gamma-ray energies

The DCF indicate a moderate correlation with no lag between gamma-ray and

optical flux variations


The contribution of ECD radiation alone cannot account for the hardness of the spectrum. The gamma-ray emission seems to be dominated by IC scattering of the external photons from the broad line region clouds

ECD

ECD

ECC

ECC



MW Observations of 3C 454.3 in December 2007

Donnarumma et al., 2009, submitted to ApJ

Simultaneous multi-wavelength campaign with the contribution of Spitzer, REM, GASP-WEBT, MITSuME, Swift, Suzaku and AGILE

<Fɣ> = ~ 250 x 10-8 ph cm-2 s-1 E >100 MeV

A leptonic EC model is considered, with also a contribution of EC on a hot corona (T=106 K),

to account for the hard ɣ-ray spectrum


DCF analysis shows a (possible) delay of the gamma-ray flux variations with respect to the optical ones of about 10 hours

The longest monitor so far of a blazar in the gamma-ray band

A factor of about 10 in dynamic range in about 2 years with a

possible spectral trend (harder when brighter)

Vercellone et al., in preparation

Mrk 421: WEBT + AGILE + VERITAS + MAGIC = …


Donnarumma, Vittorini, Vercellone et al., 2009, ApJ 691, L13

<Fɣ> = (42 ± 13) 10-8 ph cm-2 s-1 E >100 MeV

Swift/XRT: Flux (2 - 10 keV) = 2.6 x 10-9 ph cm-2 s-1

Possible correlated variability between optical, X-rays and high-energy parts of the spectrum

SSC model: hardening/softening of electron energy distribution caused by particle acceleration process

Mrk 421 from optical to TeV energies

Summary and remarks• Gamma-ray astronomy is still a largely unexplored territory,

in particular for the class of blazars• AGILE (and EGRET) detected only few objects with flux

greater than 100 x 10-8 ph cm-2 s-1? Why? Selection effects or there is a subclass of blazar with peculiar characteristics?

• SSC vs EC vs more complex models? How to distinguish?• AGILE observations has brought to light a more complex

behaviour of blazars with respect to the standard models: - the presence of two emission components in any BL Lacs

- the possible contributions of an hot corona as source of seed photons for the EC in FSRQs

• The study of multi-wavelength correlations is the key to understanding the structure of the inner jet and the origin of the seed photons for the IC process

• The study of sources in different activity states, not only during flaring states, could provide new informations

Thanks for your attention!!!

multiwavelength observations of the gamma-ray blazars detected by agile filippo d’ammando inaf -...

Documents

synchrotron emission

disk radiation

synchrotron emissionryrm

ecc emission model

external compton model

gammaray bands

gammaray blazars

seed photons