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8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI

CSS AND GPS RADIO SOURCES. 8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI. Toruń, Poland, 26-29 September 2006. Carlo Stanghellini Istituto di Radioastronomia INAF Bologna. The onset of radio activity in AGN.

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8th EVN Symposium 2006 Exploring the Universe with the real-time VLBI

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  1. CSS AND GPS RADIO SOURCES 8th EVN Symposium 2006Exploring the Universe with the real-time VLBI Toruń, Poland, 26-29 September 2006 Carlo Stanghellini Istituto di Radioastronomia INAF Bologna

  2. The onset of radio activity in AGN • Extended extragalactic radio sources have ages of several million years. • They form at the center of active galaxies and expand for up to a few Mpc outside the host galaxies. • To understand why and how a radio source starts and develops we need to find the youngest thus (intrinsecally) smallest radio sources at the center of active galaxies.

  3. find young radio sources To find young radio sources we may look for compact sources with the same morphology of the large ones (in the assumption they maintain their basic structure during their lifetime). These sources are known as Compact Symmetric Objects (CSO, < 1kpc) and Medium Size Objects (MSO, 1-20 kpc). They generally have a convex radio spectrum (flux density versus frequency).

  4. CSO/MSO and GPS/CSS • selection of CSOs and MSOs has severe problems. • They have in general a convex radio spectrum peaking around 1 GHz (CSO) or 100 MHz (MSO). • Selection based on the spectral shape is easier. • then Compact Steep Spectrum (CSS) and GHz Peaked Spectrum (GPS) radio sources.

  5. GPS CSS O'Dea 1998

  6. CSS/GPS/HFP radio sources Turnover

  7. Are these objects really young? • Youth scenario – they are young (10^4 yr). • Frustration scenario – they are old (10^6 yr) and confined. • Recurrency – they die and start again. • Short lived – they die when still young.

  8. The density in the inner kpc From X-ray, infrared, HI at 21 cm, radio spectrum at low frequency, optical line diagnostic There is not a conclusive evidence to distinguish between the youth and the frustration scenarios

  9. Evidence for youth Owsianik et al. 1998 2352+495 Hot-Spot Core Hot-Spot

  10. 0710+439Owsianik et al. 1998

  11. OQ208

  12. Polatidis and Conway 2003

  13. Proper motions Polatidis, Conway 2003 --- 10 detections (0.1-0.3 c) 3 upper limits (<0.1c) Gugliucci et al. 2005 --- 9 detections (0.4c ?), 8 upper limits (<0.2c) Dynamical ages 100-10000 years

  14. B1943+546 Determination of LOCAL spectral aging: assuming: - no reacceleration - equipartition magnetic field - no expansion losses Hot Spots Lobe Age=~1300 yr V_sep=0.28c Core Core 50pc Need pc-scale spectral index images via Multifrequency VLBA+Y1 observation 100pc Jet

  15. 1323+321

  16. Dynamical ages and radiative ages agreeand strongly favour the youth scenario but

  17. Extended emission present in a fraction of GPS Recurrency? Not always

  18. 2.7 GHZ VLBA tapered 2.7 GHZ VLBA (RRFID) 8.4 GHZ VLBA (RRFID) 1.4 GHZ VLA B 1127+145 1127+145 from mas to arcsec

  19. 0738+313 from mas to arcsec 15 GHz VLBA 5 GHz VLBI 1.4 GHz VLA B 15 GHz VLBA 0738+313

  20. What are the hosts of CSS/GPS? • CSS/GPS/(HFP) are a mix of galaxies and quasars. • Quasars rarely show a symmetric morphology, mostly core-jet at mas resolution. • Presence of weak extended emission (>10kpc) when deep observations are available.

  21. Fraction of core-jet quasars CSS Some (Dallacasa et al., Fanti et al.) GPS Half (Stanghellini et al.) HFP Most (Dallacasa et al., Tinti et al. 2004) • Incidence of quasars and/or core-jet morphologies decreases with increasing size (and decreasing turnover frequency). • Consistent with the view that the convex radio spectrum in quasars and galaxies originate from intrinsically different emitting regions.

  22. CSS/GPS/HFP quasars In the framework of evolution of radio sources from pc to Mpc scale, most GPS quasars are contaminating objects. Any inference based on complete samples of HFP/GPS/CSS radio sources should take in consideration this contamination, and should be limited to CSOs when information morphologies are available or limited to Galaxies, if mas morphologies are unknown.

  23. Even excluding contaminating objects CSS/GPS/HFP are too many. • They should decrease in luminosity by an order of magnitude during evolution (Fanti et. al 1995, Odea et al. 1997) • Existance many short-lived objects (Readhead et al. 1994)

  24. Cotton et al. 2003

  25. HFP/GSP/CSS sources become a “tool” to study the evolution of the extragalactic radio sources.

  26. Spencer et al. 89 CSS 3C/PW Fanti et al. (1990) Kunert et al. 2002 B3-VLA Fanti et al. 2001 Compact Low Pol - Stanghellini et al. half Jy Parkes – Snellen et al. 2002 Marecki et al 1999WENSS-GPS Snellen et al. 1998 GPS 1Jy Stanghellini et al. 1998 CORALZ – Snellen et al. 2004 HFPBright HFP Dallacasa et al 2000 Faint HFP Stanghellini/Dallacasa CSS/GPS/HFP samples size Flux density limit

  27. Begelman 1996 Self-similar hypothesis: cocoon will evolve with a fixed ratio of width to length Density profile Luminosity into FRI, FRII Expansion velocity weakly dependent on source size A fraction of sources die young

  28. Alexander 2000 Atmosphere with a King profile Self similar expansion No cosmological evolution of the Luminosity Function Comparison of predicted distribution functions with observational data - Samples: Stanghellini et al. 1998 (GPS) and Fanti et al. 1990 (CSS) Luminosity increases in the GPS phase (<1kpc) Luminosity decreases afterwards GPS/CSS become FRII and FR I A fraction are short lived sources

  29. Snellen et al. 2000 Samples: Snellen et al. 1998 (GPS), Stanghellini et al. 1998 (GPS), Fanti et al. 1990 (CSS) – only galaxies Luminosity evolution derived Local Luminosity Function of CSS/GPS Atmosphere with King profile Equipartition conditions, self similar expansion L increases in the GPS phase, then decreases, CSS/GPS become FRII and FR I strong comological evolution of the LF. NO need for short lived objects

  30. Tinti & De Zotti 2006 They combine several samples of GPS galaxies: Dallacasa et al. 2000, Stanghellini et al. 1998, WENSS Snellen et al.1998, Half-Jy Snellen et al. 2002, CORALZ Snellen et al. 2004, Edwards and Tingay 2004, Bolton et al. 2004 (111 objects) NO self similarity L decreases with time GPS become only FRI NO need for cosmological evolution of LF

  31. The different models are constrained by the available samples of CSS/GPS/HFP radio sources • The problem of different predictions/results arises because the different groups introduce different assumptions to put the samples together

  32. what is needed? • Selection and characterization of a large sample of HFP/GPS/CSS radio sources with symmetric morphology, at a low flux density limit, and a wide range in turnover frequency, to test and discriminate the proposed models. • Detection of proper motions in a large sample of HFP/GPS/CSS to investigate trends, make some statistics, and constrain the models New instruments are important to go to weaker flux densities and higher resolutions but a lot can be done with just the EVN, VLBA, VLA

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