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On the nature of High Frequency Peaker radio sources

On the nature of High Frequency Peaker radio sources. Monica Orienti. (INAF – IRA, Bologna). Daniele Dallacasa (UniBo, Bologna). Girdwood, 22/05/2007 Monica Orienti – Extragalactic Jets. The Goals.

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On the nature of High Frequency Peaker radio sources

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  1. On the nature of High Frequency Peaker radio sources Monica Orienti (INAF – IRA, Bologna) Daniele Dallacasa (UniBo, Bologna) Girdwood, 22/05/2007 Monica Orienti – Extragalactic Jets

  2. The Goals • Analysis of the variability, morphology and polarization of candidate HFPs; • Selection of a sample of genuine young HFPs; • What can we learn from HFPs?

  3. A sample of young HFP High Frequency Peakers • Peaks > 5 GHz; • t ~ 102- 103years • Bright HFP sample consists of • 55 objects: • 10 galaxies; • 34 quasars; • 5 BL Lacs; • 6 Empty Fields • (Dallacasa et al. 2000)

  4. A sample of young HFP Contamination from BL Lac objects • Young radio sources • No flux-density variability; • “Double/Triple” structure; • Unpolarized • Blazars • Strong flux density variability; • Core-Jet structure; • Significantly polarized Blazars may display the characteristics of young radio sources when their emission is dominated by a flare in the jet-base.

  5. 2 1 m S V= m si2 i = 1 A sample of young HFP Multi-frequency VLA observations 4 epochs of VLA observations at 9 frequencies ( 1.4 – 43 GHz) (Si – Si) • Galaxies V<3; • 21 sources (18 quasars and 3 BL • Lacs) V >>3; • 12 quasars no longer show a peaked spectrum;

  6. A sample of young HFP VLBA observations • Two-frequencies VLBA observations • In the optically-thin part of the spectrum • We find that: • 27% “Double/Triple” morphology; • 12% “Core-Jet” morphology; • 61% Unresolved • Orienti et al. 2006a, A&A, 450, 959 a =0.2

  7. A sample of young HFP Polarization properties • From simultaneous VLA observations at • 4.5, 8.4, 15 and 22 GHz + information • from the NVSS at 1.4 GHz, we find: • 57% have fractional polarization >1%; • 36% are completely unpolarized; • All the galaxies are unpolarized; • 70% of quasars are highly-polarized.

  8. A sample of young HFP Results From the flux density variability, morphology and polarization we find that: Quasars are: Variable; “Core-Jet” morphology; Polarized emission (>1%). Galaxies are: No Variability “Double-Triple” morphology Unpolarized or slightly (<1%) polarized Only 25 from the HFP sample are still young radio source candidates

  9. Constraining the radio source evolution HFPs and the source growth Strong flux-density and arm- length asymmetries in compact (< 15 kpc) radio sources

  10. n r -β n0 2 ncl ncl vj,c v n0 9 8 ncl Lj,c l n0 t3 t2 t1 t0 t1 t2 t3 Constraining the radio source evolution The evolution model The source growth in an ambient medium with a King-like profile: Jet-cloud interaction: t -1/2 (NLR) v  Const (ISM) t 5/8 (NLR) L  t -1/2 (ISM) Asymmetries cannot be reproduced

  11. Constraining the physical conditions Magnetic field RXJ1459+3337 From equipartition: Heq ~ 0.16 G Direct measurement: H~ 0.150.03 G From X-ray luminosities: H~ 0.14 G Consistent with a source in equipartition condition with X-ray luminosity due to Synchrotron Self-Compton

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